Intermittent fasting, cortisol and blood sugar


There’s been a lot of discussion about the benefits of intermittent fasting (IF) in the paleo community lately. Paul Jaminet mentions it’s role in boosting the immune system in his book, The Perfect Health Diet, and IF can also be helpful for those trying to lose weight and tune their metabolism.

From an evolutionary perspective, intermittent fasting was probably the normal state of affairs. There were no grocery stores, restaurants or convenience stores, and food was not nearly as readily available or easy to come by as it is today. Nor were there watches, schedules, lunch breaks or the kind of structure and routine we have in the modern world. This means it’s likely that our paleo ancestors often did go 12-16 hours between meals on a regular basis, and perhaps had full days when they ate lightly or didn’t eat at all.

So, while I agree that IF is part of our heritage, and that it can be helpful in certain situations, I don’t believe it’s an appropriate strategy for everyone.

Why? Because fasting can elevate cortisol levels. One of cortisol’s effects is that it raises blood sugar. So, in someone with blood sugar regulation issues, fasting can actually make them worse.

I’ve seen this time and time again with my patients. Almost all of my patients have blood sugar imbalances. And it’s usually not as simple as “high blood sugar” or “low blood sugar”. They often have a combination of both (reactive hypoglycemia), or strange blood sugar patterns that, on the surface, don’t make much sense. These folks aren’t eating a Standard American Diet. Most of them are already on a paleo-type or low-carb diet. Yet they still have blood sugar issues.

In these cases, cortisol dysregulation is almost always the culprit. When these patients try intermittent fasting, their blood sugar control gets worse. I will see fasting blood sugar readings in the 90s and even low 100s, in spite of the fact that they are eating a low-carb, paleo-type diet.

That’s why I don’t recommend intermittent fasting for people with blood sugar regulation problems. Instead, I suggest that they eat every 2-3 hours. This helps to maintain stable blood sugar throughout the day and prevents cortisol and other stress hormones like epinephrine and norepinephrine from getting involved. When my patients that have been fasting and experiencing high blood sugar readings switch to eating this way, their blood sugar numbers almost always normalize.

I don’t think eating every 2-3 hours is “normal” from an evolutionary perspective. But neither is driving in traffic, worrying about your 401k, or staying up until 2:00am on Facebook. The paleo template is there to guide us, but it’s not a set of rules to be followed blindly. This should also be a reminder that there’s no “one size fits all” approach when it comes to healthcare. Successful treatment depends on identifying the underlying mechanisms for each individual and addressing them accordingly.

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Comments Join the Conversation

  1. Lins says

    Hi Chris,
    I am 34 and was diagnosed with Type 1 diabetes 18 months ago. Shortly after diagnosis I switched to paleo and low carb and only require occasional insulin if I have a high carb meal or for a few days each month around my period when my fasting blood sugar tends to be higher than usual.

    My problem is that when I take the long acting insulin I feel physically edgy and my body is tense all day long even though my blood sugar levels are normal. This happens even if I take long acting insulin outside of the time of my period.

    I am wondering if this is related to cortisol dysregulation? It does not occur when I take rapid acting insulin such as with a high carb meal and when I’m not taking long acting insulin I feel great!

    For months before and shortly after diagnosis of Type 1 diabetes I had this same constant nervous tension (even before I went paleo/low carb so I haven’t linked it to my diet). No one was able to shed any light on it for me and the only test results that showed anything were that my salivary cortisol levels were very high all day long. I have only recently linked this same feeling to when I take long acting insulin so I believe it is somehow related to autoimmune/diabetes.

    I have had no luck in getting any insight from my endocrinologist so any help would be much appreciated!

  2. Dale says

    I’m a 69 years old male, I’m on hormone therapy combating prostate cancer. My fasting glucose level, is between 90 to 97. The side effects of hormone therapy is weight gain and increase belly fat. I also think that it has effected my glucose level, like increased it. I am hoping that IF, can offset some of these side effects. I am vegan, no meat or dairy.

    Will IF help as I hope? I just started the eating plan, yesterday, with a 16hr fast. How long do does it take to see some measureable effects, if there is to be?

    • Gloria Cole says

      Dale. What intermittent fasting really does is reset your insulin which may be off from following a high carb junk food diet. You may not be a candidate. It looks like your “problem” is really an effect of the hormone therapy. Is there any way you can work with your doctor to cut back some on the therapy your are doing? And check with your doctor to see if fasting might interfere with the therapy. (Make sure he isn’t just giving you a knee jerk reaction, Oh fasting! That can’t be good!)
      Your fasting blood sugars are ok, probably healthier to be in the 80s, rather than the 90s. As you say they may be running a little high because of the therapy. If you want to try IF you should see results in a few weeks. And results would be slightly lower blood sugar, and less belly fat. You will be burning fat instead of glucose. Also, you want to eat a variety of good fats (oils, nuts, seeds), along with your regular vegan fare.

      • Arod says

        Hello Gloria and all of you IF people, just wanted to give an update on my progress after using the IF method to reverse my type 2 Diabetes, I’m so happy to say that my numbers have changed dramatically. My fasted blood sugars were out of control (over 300) and now since I’ve gotten on the IF diet, my numbers are no more than 120 and sometimes under 100. I have to admit it does take work for your body to adapt but it eventually it will, combining HIIT (high intensity interval training) workouts, along with IF and a fully committed KETO diet, you will be amazed at what you can achieve. I wish that some of my closest family members that have deceased because of Type 2 Diabetes would of known about this, they never stood a chance, I just feel so blessed that I found out how I can fight back and “kick type 2 diabetes ass”. I currently feel “leaner, faster and stronger than ever. I thought I could never stop drinking soda and now I don’t even crave it lol. I can’t wait for my follow check up with my Dr and brag about my numbers because he thought that my diet was extreme and immediately wanted to put me on insulin, Actos and merformin. But I declined I told him let me try my IF method and if this doesn’t work then i guess I’ll have to start heavy meds, so 3 months later “bam” Don’t need those meds, I stayed with metformin but to be honest with you guys, that pill really doesn’t make a difrence so when I go back I’m going to tell my Dr that I want to try 3 months without metformin or any diabetic medication to see my results. Here’s my iF process on mon, wed and thurs I hit the gym at 6am I combine weight training and cardio with HIIT workouts, 9:30 i’ll drink my black coffee and won’t eat until 2pm, then my last meal at 8pm, but before all that you need to consider watching your cortisol levels and also monitoring your sugars 3 times a day, to see what foods really spike up your sugar, but anyway just giving you guys my update and I hope someone here will take the time and read this to be as blessed as I did, to learn this knowledge, thanks guys and good night.

        • Gloria cole says

          Wow! Arod. I am impressed. Shows what can happen when you take reversing diabetes seriously.

          One question: Watching cortisol. How do you do that, and what do you do if your cortisol is running your blood sugars up?

    • Dale says

      Update from my previous post. Two weeks after I started an IF regimen from 6pm to 9am, I check my blood glucose. I was consistently over 90 and my first check this morning I’m at 74. Hopefully, I can contribute this improvement to the new regimen. Its never since I have been checking has it been that low.

      • Gloria Cole says

        Yesterday I listened to a presentation between Brian Mowl (diabetes educator) and Dr. Jason Fung. Fung is a proponent of intermittent fasting. I tried intermittent fasting and essentially reversed my Type 2 diabetes. The only remnant is high morning blood sugars. I am inspired by what Dr. Fung said yesterday: Its a back log of sugar. Just keep fasting and eventually you will use it up and your body will be normal once again. Dale, I am envious of your 74 morning blood sugar. And I am going back to my fasting routine to see if I can accomplish the same. Who knew that that curing diabetes could be that simple?

        • Dale says

          Gloria, I am seeing my step brother today. He has type 2 diabetes, his glucose values are over 300. How much of an impact can IF have on a guy like this? When you were type 2, how large were you glucose numbers.

          • Gloria Cole says

            Dale. If he has glucose numbers over 300, either he is newly diagnosed and in denial about the seriousness of this disease, or someone has convinced him to manage his diabetes with insulin and he hasn’t a clue about the dietary changes he needs to make. I was on insulin briefly, but I wound up with bg numbers in the 40s, and faced passing out. Finally, the endocrinologist put me on metformin, only.
            i don’t think Ive ever had numbers in the 300s–because I am pretty careful about what I eat. I have pretty much been off sugars, grains, and processed foods, even before I was diagnosed with diabetes. My diagnosis followed a period of severe stress (job harassment). And stress is significant for diabetics and anyone living with a chronic disease. As for your step brother, if he is on insulin, that may be a complication, be cause he is going to have to commit to the necessary diet changes, and then wean off the insulin. Also, people get attached to the bad food they are eating. And no one likes to make changes away from their familiar things. I am sure IF is the way to reverse Type 2 diabetes, but it does require some commitment and determination to get well. Search for some basic articles on EF. I find the “window” method easiest, rather than fasting whole days at a time. Just define the hours you are going to eat, and then don’t eat the rest of the time. Dr. Jason Fung says it doesn’t matter, any mode of fasting will work. But, the foods eaten when you do eat have to be the highest quality- no processed foods, sugars or grains. And, thanks for caring about this guy. I hope he decides to do what it takes to get healthy.

            • Dale says

              Hey Gloria, I spoke with my step-brother about his situation. He is not taking insulin but is on metformin. He is on a low carb diet. He is also kind of on a non-regimented fasting regimen. I believe he has been doing for 1 to 2 months. His fasting glucose is now 370+. If he is truly doing what he says, should he be having better results than this? He has lost about 35lbs, he’s a big guy. I would say hes 240lbs. He is also 76 years old.

              • Gloria Cole says

                Dale. I am 75, and one thing Im learning is there is life after 70. I mean 70+ year olds can and do have a right to be healthy! I have also found that fasting seems to trigger high morning glucose levels–for me its in the 160s to 180s even though I haven’t eaten since 4 pm the previous day. Dr. Jason Fung recently spoke about this (Q&A with Brian Mowl). He says its just that we have a large sugar reserve, and the solution is to just keep eating right –off processed foods, eating mostly fruits and vegetables, and fasting, until the reserve is depleted. Metformin is a good strategy–at least according to Life Extension Magazine. It not only keeps insulin levels low and regulates insulin resistance, but it also is antagonistic to cancer. And for diabetics–with all the excess sugar we have–cancer is an ever present danger. I would say he is on the right track. And he is so lucky to have your support.

  3. Kadz says

    I’ve always wondered about this topic.
    I’ve tried IF in the past and maintained it for a long time. I was mainly doing the bullet proof diet which consists of high fat and protein diet, very low carbs. First I lost some weight then I stalled. During that whole IF daily, I was ready to faint. Right now I weigh about 125lb and it fluctuates. My last meal was last night 7pm and today I haven’t eaten since 5. Usually if was doing the IF correctly I would start eating at around 3:30. But around 12pm I was ready to faint. So generally if I don’t eat anything for breakfast I get tired, dizzy, spinning head. I’m prone to low blood sugar. But if I have let’s say a normal ice cream I kinda get little excited lol.
    Any advice would be appreciated.
    Oh my current diet is fair amount of carb, (I train Brazilian jiu-jitsu almost 5 days a week twice a day) and grass fed fat.
    Thank you!

    • Gloria Cole says

      Kads. I would suggest looking at A. Christianson’s Adrenal Reset Diet and then incorporate those principles into IF – eating within a restricted window each day. When you go with out eating you bring cortisol into play. You can’t eat ice cream (not normal) on an IF diet. it is essential to eat very high quality food, because you are trying to reset your system here. If you trigger insulin, you are going to get low blood sugar. And. As Christianson suggests, you may need to eat more carbs (good quality) with fiber at the last meal. Good luck. Sounds like you need to make a few adjustments to make it work for you.

  4. Jesse says

    Thanks for all the amazing info. Hope I am not missing something with this question…

    My fasting glucose is 85. (is this a normal, high or low number?)

    2 hours after I eat my BG goes to 110+ and I get incredibly tired and foggy headed. The only way to remove the symptoms is to take a 20 minute nap. (is 110 a normal, high or low number?)

    My #1 goal is to stop these spikes and fatigue episodes.

    I never eat breakfast, just bulletproof coffee, then eat a paleo lunch and dinner (high protein and fat, low carb).

    I drink alcohol often…

    Carb cravings every day at 3PM.

    Would you describe my condition as insulin resistance, reactive hypoglycemia or a cortisol problem?

    I am generally happy but don’t get enough sleep. Stress levels are fine.

    Thanks for any info.

    • Gloria Cole says

      Jesse. Fasting glucose of 85 is a good number, and a post prandial (after meal) blood glucose of 110 is also a good number.
      As for the fatigue you might want to check out Alan Christainson’s Adrenal Reset Diet. he recommends a high protein breakfast (can be a shake), a green leafy lunch with protein, and a relatively high carbohydrate dinner (no junk) for optimum adrenal function and energy. He also has information on resetting circadian rhythms. That should fix your fatigue and energy issues. Lean about healthy carbs–fruits and vegetables and incorporate them into your diet. Alcohol–I would cut back and aim for one or less per day, Alcohol can really mess up your energy, not to mention mess with your liver and your head! Aim for 7 to 8 hours continuous sleep. Sleeping is for regeneration and repair. It should be high priority.

    • Sarah Hie says


      Those are great numbers and don’t suggest any blood sugar issues. If you’re concerned, try eating a highly carby meal of around 50-60 carbs from starches and fruit. Test your blood sugar at 1, 2, and 3 hours. If your readings are no higher than 130 at 1 hour and then begin to drop back down, you’re likely just fine and don’t need to worry about your blood sugar. The fatigue might be from some adrenal issues (as Gloria already said) and I second her opinion about alcohol. A nightly glass of wine or whatever might be completely fine for you, but I would be cautious about anything more than that – and I would certainly take out all alcohol for at least 30 days and see if that helps.

  5. Arod says

    Hello I want some advice, I’m a thin type 2 diabetic (5’4 134 lbs) , very new to the “Keto” diet, I’ve been on it for 3 weeks and emedietely saw my glucose go down, used to be in the 300’s high sugar levels, now currently down to the 140’s max, but anyway is intermittent fasting recommended for type 2 diabetics, I workout 3 times a week in the mornings on an empty stomach since 8pm the day before, I workout for hr and a half ( weight resistance and running intervals) I feel great so far and I know I still have work to do, eventually my goal is to have fasted sugar readings under 100, but anyway another question, when I workout my sugar levels tend to go up, by being on a low carb diet, will my body eventually switch and start lowering my sugars? And if so for how long and if not is there anything I can do to stop this from happening?

    • Gloria Cole says

      Arod. Question # 1. Intermittent fasting is recommended for Type 2 diabetes. It should reverse the disease. Keep in mind that your fasting blood sugars do not only reflect the carbs you are eating, it also calls into play gluconeogenesis wherein morning blood sugars are elevated due to the action of cortisol causing the liver to make glucose out of proteins and fats. Intensive exercise will raise blood sugar also, and this also involves pathways other than carb restriction. I don’t really understand your second question. On a non-ketogenic diet, your sugar levels go up, but on a low carb diet will your body starts lowering blood sugar levels and how can you prevent this?

      I understand the goal of ketogenic diet is to train into fat burning as opposed to carb burning as a source of energy. Since you are already lean, you may want to modify the ketogenic diet so it works better for you, since you don’t have that much fat to burn. Iintermittent fasting is good for “resetting” and unbalanced immune or hormone system. Above all, eat high quality food and space it such that during the time you are eating, you have enough fiber, carbohydrate, and protein in your last meal so that you are not triggering high cortisol levels during your fasting period. The point of fasting is not to starve, its just supposed to reset mechanism that have gone haywire for some reason–usually bad food.

      • Arod says

        Thank you Gloria I will definitely take your advice in regards to my Keto diet. I’m sorry about my 2nd question, but you pretty much answered it. But you know what was weird is that I felt I knew more about my type 2 disease than my Dr. He was telling me that the only way to lower my blood glucose would be by medication and maybe in the future get some insulin. When he said that I knew he didn’t understand my disease like me… From what I know is that too much insulin would make things worst, but anyway we did some blood test today and i don’t expect good numbers since I just barely started my Keto diet 3 weeks ago but I will be seeing him back in 3months. So far I only take metformin 1k ml 2 times a day (1 morning and 1 night) and 1 baby aspirin. I hope that with my momentum I will prove my Dr. Wrong and will soon not need medication to lower my gluccose levels, I have started eating big meals on my eating window low carbs high protein, another thing, my Dr. did mention that I shouldn’t worry about eating too much protein, that if anything I should make that a priority since my diabetes triggers my body and supposedly that’s why I’m a thin type 2. He said my body needs more insulin, but I say I just need to be more insulin resistant, I was just so disappointed how quick my Dr. was add more medication vs letting me try to fight this naturally but anyway thank you once again, I truly appreciated and I will keep an eye on that cortisol as well, I feel awesome so far, thank god I haven’t had any complications yet.

        • Gloria Cole says

          Hi Arod. Im amazed that you are diagnosed with diabetes 2 at all since you are lean-5.4 134 lbs and working out. Unless you were eating really bad food, there must be something else going on to get your blood sugar up into the 300s. I think you will see results soon if you adapt to a plan of intermittent fasting. Unless you have other reasons for going ketogenic, I would even out to a more balanced diet — leafy greens in the carb category at least. Most nutrients are in vegetables and fruits so if you don’t eat any, you can set yourself up for some nutrient deficiencies. Ive found when doctors start loading you up with drugs its time to move on. And when they start suggesting surgeries you don’t need-run!

          Don’t know what the baby aspirin is for. It may do more damage than good. And insulin for a type 2 diabetic is like prescribing alcohol to an alcoholic. Its the last thing you need. Insulin use can lead to “double diabetes” you lose your a bility to make insulin and become both Type ! and Type 2 at the same time. Note. I am not an M.D. I am an anthropologist and I do have diabetes (or did have before intermittent fasting). So for what its worth … here’s hoping next time you will be report to us on your good health!!

          • Arod says

            Thanks Gloria and I will definitely keep you guys posted on how I will overcome this disease. But as far as how I caught this was hereditary (Dr. Explained) because both of my parents are diabetic and eating a lot of fast food must have triggered something in me.

            • gloria says

              Arod. Recent studies in epigenetics show that genes (as in Type 2 diabeltes) allow but do not determine a disease pathology, so saying that you have Type 2 diabetes because of your genes is a cop-out. its not like blue eyes. The reason you have diabetes (Type 2) is from your own behavior and environmental pressures. And you can recover from the disease by learning to eat nutritious foods (instead of nutrient depleted and toxic foods), and getting a moderate amount of exercise. There is probably a psychological component in there also. A lot of it is just learning to respect your own biology. Good luck.

              • Sarah Hie says

                Sometimes things ARE genetic and while we can make modifications to optimize our health, telling an active, lean individual that they’ve done something to cause their diabetes is very unhelpful. Despite a very careful diet, I have blood sugar issues that have amplified during my pregnancy. My doctor isn’t concerned because I “passed” my OGTT, but just barely. Once I started monitoring myself with my glucometer, I learned that my fasting glucose is always between 90-95 (it should be in the 70s while pregnant) and very low carb meals still bring me up to 120ish for hours – even after 3-4 hours sometimes. I reduced my carb intake from 100 grams per day to 50-60 grams per day and took out all starches. I keep 1 serving of berries a day just to stay sane. If I eat anything carby (yes, I mean the good ones), my blood sugar spikes into the 140 range and stays there for a while before making me feel sick and shaky. I didn’t cause this by eating too many bananas and sweet potatoes. It’s more likely connected to a) my reaction to pregnancy; and b) my mother’s daily tray of butter tarts when she was pregnant with me (resulting in insulin resistance from day 1). I also have issues with high cortisol which I am sure contributes and which I am working on.

                • Gloria Cole says

                  I agree with Sarah, especially about the alcohol. I think the major problem here is that we are worried about blood glucose, when the real problem is insulin–too much of it. But we have no way to measure it.


    Hi, I am a 44 yo female dx’ed with late onset congenital adrenal hyperplasia in Sept of 2009, I have done search after search and haven’t found any information telling me if I should or should not be doing IF.
    My adrenals do not make much cortisol, it all goes to androgens which is why I have had a higher testosterone level all of my life. I was on prednisone for a few years but decided to wean off of it because I was not seeing any benefit of being on it.
    I have been doing IF for almost a year now. I was seeing great results at first but I am back up about 5-10 lbs over my maintenance weight. I am 5’5″ and right now weigh about 125 which is ok with me I just don’t want it to get any higher. I also have hashmoto’s thyroiditis.
    So my question is should I NOT be doing IF with this condition? Or can you point me in the right direction to do more research?
    Thanks so much.

    • StaLo says

      I have the same diagnosis, but no thyroid issues. In paleo code he does not suggest doing IF for thyroid issues. Do you trend toward low blood sugar or symptoms of low blood sugar? For then you would want to eat every 2-3 hours. The only supplements that worked for me was Chinese medicine….i did all the adaptogenic herbs and stuff for cortisol there was…but that did not work for me, and many made me feel worse.

  7. tony justman says

    I’ve been doing IF for about 2 years and started on a ketogenic diet in Jan 2015. I have noticed my FBG to be in the 85-100 range in the a.m. But my Hba1c just tested at 4.5 so I have a hard time seeing that I’m insulin resistant.

    I’m no expert, but I’m not so alarmed given these facts, especially given that my BG will continue to drop throughout the morning until I break my fast. I see something in the range of mid 50s to high 60s by that point, depending on when I eat.

    this lays out an argument that this higher, early morning FBG is a natural adaptation when one gets adept at metabolizing fat:

    It’s intuitive to me that my body has adapted to a low-carb, fat burning state where I might fast 16-20 hours and even do an intense workout in the middle by scrounging up or sparing glucose. I don’t see how this is “insulin resistance” when overall there’s never that much glucose floating around in my blood stream (HbA1c test shows that). It more like my body has a plan B now that it has the option to burn fat or use glucose.

    There’s the cortisol angle, I suppose, which might mean that I’m unduly stressing my body, so it’s something I intend to watch. I’m probably going to play with adding some more carbs in a dinner more consistently to see what that does to FBG….

    • Gloria Cole says

      Tony. I like the idea of high FBG driven by cortisol as Plan B.
      I am type 2 diabetic and my A1c’s so far during intermittent fasting were 5.4 and more recently 5.7, at the same time my FBG hs gone haywire 170 or 180 on some mornings. The IF plan Im using to the daily window routine — I eat between 10 and 4 pm. This was a problem and this is when the high FBG occurred. So now Im shifting to finish eating later in the day and fasting later in the morning. I don’t have the results yet. I am hyperthyroid. I don’t see a good reason not to use a mild form of IF with hyperthyroid. i am losing some weight, but it is not excessive. And I am determined to reverse my diabetes. Somehow I think if I get rid of the diabetes, I will also get rid of the hyperthyroid issue. I never have low blood glucose on my monitor, but I still get a radical cortisol surge with gluconeogenesis, running morning fasting blood sugars sky high.

      • Susan says

        I have always had high morning blood sugars, whether my A1C was low or not. I find that eating something around 10 at night lowers the morning BS a great deal: normally 150 or above – this morning it was 110. The numbers have really come down with the keto diet. I starter IF last week so I hope to see a big improvement in the BS levels.

        • Gloria says

          Susan. I think you will see amazing results with intermittent fasting. The problems you may encounter are high fasting blood sugars due to morning cortisol. Hunger isn’t a problem after a few days. While some people recommend eating frequently –every 2 or 3 hours to control blood sugar–I think this is mainly if you tend to hypoglycemia. For me that just shoots my blood sugar up into the 300 range where I dont want to be and do not feel well. I think the key to high morning blood sugar is to eat a relatively high carbohydrate meal for your last meal of the day, and include lots of fiber with it. Maybe even a fiber supplement such as inulin or glucomanan. A good guide to controlling blood sugars set off by cortisol is Christianson’s Adrenal Reset Diet. Incorporating circadian rhythms with intermittent fasting I think is the answer. I dont think eating frequent meals is a good idea for someone whose glucose control is problematical–based on my own experience.

          • Susan says

            Yes, eating something with a little carbs works best for me for my last meal. The night before last I ate a small nectarine (1/2 of my carbs for the day!) at the end of my window. Yesterday morning, the numbers were 88. The key is to not eat too many carbs or the numbers are higher in the morning!

  8. Mindi says

    Thank you so much for this posting. I know that I have blood sugar regulation problems and have not known how to resolve them. I appreciate the advice to eat every 2-3 hours- makes sense to me, as I feel like I could eat all day long. The challenge is to figure out how to do this on such a restrictive diet. I am following the Autoimmune Paleo diet, the Candida diet, and also a low-oxalate diet. Based on these restrictions, there are only about 15 foods I can eat. I also have to be careful to rotate my foods because of food sensitivities. Does anyone have ideas how to eat frequently on such a restrictive diet? Recommendations for a nutritionist? I would be grateful for any suggestions. Thank you.

    • sal bisslessi says

      I would advise everyone to get on a low carb, high fat and protein diet. And than after a few moths, begin intermittent fasting. You will find doing both will be tremendous.

      Eat your fruits and vegetables and keep your carbs between 50-100. You will melt away fat and health problems. You will be amazed. EAT WHOLE FOODS. This is a perfect fit for everyone. Try it.

      You see, fasting gives your body a rest period, and releases all kinds of wonderful hormones, fat burning, muscle building hormones that will burn fat in your body. Doing both will keep insulin levels very low.

      • jj says

        That is good advise however doesn’t always work. I have sluggish adrenals and liver detoxification and if ..even after ketogenic for years causes my blood sugar to sky rocket.

      • Michael Alber says

        Sal: I guess you didn’t read this article. Chris Kresser says fasting can cause cortisol levels to increase and affect your blood glucose. Funny, I guess you missed that Chris recommends not to do fasting if you have blood glucose regulation problems and to eat every 2-3 hours.

        • markku says

          But IF has been shown to improve insulin sensitivity.. so if you keep eating ever 2 to 3 hours you are not teaching your body to deal with the problem.

          • Michael Alber says

            I guess it is true to teach your body about dealing with fasting but everyone is unique. First of all we don’t live in the same world as our ancestors so I believe you have to stay on top of what you eat and the chemicals around you. Fasting today is different than our ancestor since anything affects cortisol levels. I’m finding personally cortisol is a problem with my own health problems. I believe stress is a big a factor in our modern lives.

            • musings says

              I sense the problem might have to do with different genetic problems associated with the pathways involved in processing glucose. The glitches may be at different points for different people, with various hormones as potentially flawed. One of the places this is being studied is the Salk Institute. So different genes for different people that control these hormones may be implicated.

              I myself am overweight and I get some activity, although in the recent winter, not nearly as much. My A1c went from 6 to 8 in this period and I have been prescribed Metformin.

              Meanwhile, I know that in the past I did well with intermittent fasting. I believe that my weight gain made me not so much unstable in blood sugar readings, as predictably lousy.

              For now, my solution will be to make sure each meal is calorically less because even if I think I am getting enough activity (say 2 miles of walking per day on average), this is not adequate to deal with the problem until there is significant weight loss. Twenty pounds off, if carefully maintained (not like the last time I did this), will help. Also, probably some vitamin supplements. I know that my family has a lot of type 2 – my grandfather, mother and half my siblings. The grandfather lived to be much older than the average in his day (83) and my mother is alive at 91 (though blind – which is soooo scary for me – it happened in a cascade when she was about 87, perhaps partly to do with a shock to her system with cataract surgery – don’t really know). We may have some “thrifty genes” which allowed ancestors to get through long periods of near-starvation. But like sickle cell anemia being protective against malaria, this kind of diabetes may have saved lives which later were shortened when food was more freely available. However in our having Type 2, my family is not so unusual for Americans since it is rising here.

              Here I am at my laptop, and the level of sitting during a New England winter is far too much to be healthy in any case. There have to be some guidelines – like getting up for several minutes of any hour for all chair-workers. One burst of exercise in the day, as we know, does not help enough.

          • Jer says

            I have IF’d for 3 years – skipping breakfast, fasting 16 hours a day. Every year my cholesterol gets better, and my blood sugar worse. Over 3 years it’s gone from 99 – 107 – 124. I’m going to give breakfast a shot, and maybe even eating every 2-3 hours.

      • Kip says

        Absolutely disagree. I have been on a strict ketogenic diet for over 100 days. My blood sugar would not come down. Then I tried intermittent fasting and the same results. There are those who do not gain control of their sugar levels. This is not a theory but my own experience, regardless how much sense it makes – IF. My blood pressure increased and my sugars would not drop. I appreciate the article because it makes sense. IF is not for everyone. I am one of those.

  9. says

    I have a feeling that one of the answers to the increase in blood sugar might lie in Stephen Gordon’s post further up the page.

    We are broadly applying the thinking that ‘paleo’ or ‘IF’ etc diets may be helpful because they are more in line with the nutritional environment that we evolved for. It would then make sense to modify other aspects of our life in the same manner.

    Perhaps the increased blood sugar that results from these diets is actually a natural healthy response if we look at the big picture. Maybe our body is moving back towards its natural apex physiology which suits a much higher/intense activity level (hunting, gathering, fighting predators etc) than we are exposed to in modern sedentary society?

    I think Boyd-Eaton(?) had some papers on the activity levels of indigenous/paleo peoples compared to today’s society. Showing that the old “30 minutes of moderate exercise 5 days a week” was nowhere near the levels of activity required to trigger healthy cell function.

    In fact the 30 minutes thing has only ever been the bare minimum required to avoid a diagnosed sickness – which is actually a totally different goal to creating health.

    I wonder how many of the people here have introduced a lifestyle change to a fairly high/intense activity level such as Stephen Gordon’s boxing training etc alongside the IF nutritional changes?

    Also, what about the mental-emotional component of our lifestyle. If this is not also changed in a manner that honours health it can easily contribute to amplified/misplaced endocrine responses. This could also make an otherwise healthy diet appear to be unsuitable?

    Everything is connected – the way we eat, the way we move and the way we think are all interrelated when it comes to non-linear endocrine and neurological feedback loops. Helping the body make its way from high allostatic load back to homeostasis requires an orchestration application of lifestyle change.

    Hence, I wonder if it is not so much a failing of the IF diet, but an erroneous expectation that a nutritional change alone is a fix-all solution a highly complex problem… Seeking to make food a natural ‘medicine’ to fix a diagnosis, rather than seeing it as an integral aspect of a living environment which facilitates for the creation of health.

    Without requisite changes to the interdependent physical and mental-emotional aspects of life we may be compromising or confounding the IF/paleo diets elgance or effectiveness.


  10. Larry says

    Yes doctor, you’ve got the answer why my blood glucose is much more higher at the end of the day than when I get up during fasting.

    I’m so confused whether to take my medicine or eat my low-carb diet or what? Now I’ve got it to to eat every 2-3 hours but moderate amount of food.

    Is there some way to control or reduce cortisol during fasting?

  11. Laura says

    TL;DR: I’m an archaeologist. The paleo-diet is not “one size fits all.”

    I’m an archaeologist who specializes in the studies of diets of hunter-gatherers. I’d say eating every few hours is actually pretty normal. Hunter-gatherers spend a large amount of time foraging, during this time they’re snacking more or less constantly. Like, if you go out picking berries, you’re not going to snack on a few? Also, hunters would usually take food with them.

    What we have to remember is that the hunter-gatherers you see today are disadvantaged, fourth-world peoples who have been forced into marginal environments. Many of our ancestors lived in much more accommodating environments.

    Furthermore, hunter-gatherers live (and lived) in wildly variable conditions, with wildly varying diets. The Inuit eat 90% meat whereas the San eat 90% plants (give or take). If your body tells you to eat every few hours, then do it. It might have something to do with hundreds of thousands of years of your ancestry.

    • Gloria says

      Hi Laura. I am an archaeologist, also, and thanks for setting the record straight. Our ancestors normally had plenty to eat. They did not normally spend a lot of time starving. If they did, they would not be us!

  12. Al says

    Hey thanks for the post. It was very helpful.

    Over the past 3years, I have lost about 30lbs by just eating meat and vegetables with regular exercise. I am a 5’8″ male and weigh about 210lbs.

    I believe I hit a plateau. I am looking into intermittent fasting. I want to start very slow. I find that I have more bowel movement when I fast, once/week. I came to use fasting since I found that after about two weeks of intense/cardio exercise (5x/wk) and eating 3x/day, I was tired and my weight fluctuated between 205-210lbs.

    What are your thoughts?

    thanks so much again !

  13. Melissa says

    I just switched over to a 30 day paleo meal plan from “Practically Paleo” from a typical diet high in carbs and sugars. I have PCOS and to help prevent insulin resistance I am on metformin 500mg twice a day. My question is this: I am 4 days in and seeing spikes in my blood glucose levels. I monitor with a meter as you suggested in one of your articles. I typically have very normal non-diabetic numbers for blood glucose. Now I am seeing my baseline at 93-95 and my fasting at 100. Is this typical? should I see it level out and return to my old levels if I just stick with the paleo diet?

    • says

      . getting too much protein can work against the metformin
      by raising glucagon that increases liver-made sugar;
      remember, the magic of the Atkins diet
      in the way it lowers blood sugar and cholesterol
      is not just from being low in carbs,
      but also by being high in fat
      rather than high in protein .
      . try getting less than 50g protein per day;
      and get more gentle, low-glycemic carbs
      like greens, cabbage, broccoli … .
      — peas are a low-toxicity, nearly-Paleo legume
      and hence a good carb according to the Perfect Health Diet .

  14. Gloria Cole says

    I have been intermittent fasting for several years now. I stop eating at 4 pm and start again around 9 or 10. I would not eat every 2 or 3 hours — that would only run my bood sugar up. For me eating is a problem, I feel much better when I dont eat. I eat 2 or 3 small meals a day. More ketogenic than paleo. I am diabetic and hyperthyroid. I am now off insulin. A1c 5.4. So Im still working on diabetes. This summer I started having unreasonable fasting glucose readings–to 180. It turned out to be due to deydration — and a faulty blood glucose monitor. I can recommend IF as a means to deal with diabetes.

    • Janet Ruffin says

      Hi Gloria,
      Thanks for your post. Can you clarify your IF for me? You stated that you stop eating at 4pm and you start eating at 9-10. I assume that is 9-10 AM but don’t want to assume….

      I have been doing IF from 8p-about Noon…. having my first meal at lunchtime. The morning I am drinking some bulletproof coffee. Gets me through the morning fast…

      Trying to get my morning BS’s below high 90’s. Some days it is and others it isn’t. Having quite figured out the trick yet….
      I’ll just keep on working at it.

      • Gloria says

        hyperthryoid. No. In fact its worse. Yesterday, the M.D. recommended radiation therapy to destroy my thyroid gland. Also, high morning blood sugars continue. I like intermittent fasting. To me its simple to do, and it does keep my insulin levels low–so A1.c 5.4 tells me there is something right about the method of IF I am using. I don’t want to eat every 2 to 3 hours. It seems to me this discussion is focusing on blood sugar, when the real problem in diabetes is insulin.

    • Gloria Cole says

      Well this is June, 2015. The high fasting blood glucose problem continues. I replaced the monitor, and I am trying to drink more water. My fasting blood sugar is sometimes as high as 180. Clearly there are endocrine complications. In addition to the not controlled diabetes, hyperthyroidism has kicked in. I didn’t need to lose weight, but I did lose 20 lbs –and atrophied muscles are starting to show. Also bulgy thyroid eyes. You would not want to meet me on a dark street at night! Houston. There is a problem! Yes I do have chronic stress, from the apartment complex next door–a blaring stereo 24 hours a day.

  15. anna says

    Sigh! I eat a low-carb, ‘clean, wholefood’ type of diet (spend quite a bit of time in nutritional ketosis), and I fast daily for about 18 hours, plus a 24 hour fast weekly.

    I LOVE fasting – it gives me a sense of control, and wonderfully level energy, and for the first time in my life, I am free of cravings.

    But my blood glucose sux – fasting can be as high as 7, and I spent most of the day at around 6. It drops to 4-5 soon after eating (the strange patterns you mentioned). HBA1c has gone 34mmol/mol -> 35 -> 37 over the last year (which my Dr says it completely normal, as is my BG).

    I am very frustrated – I desperately don’t want to stop fasting and go back to feeling out of control, hungry, and like I am on an energy rollercoaster.

      • anna says

        Except I’m pretty sure I am not high protein – I am a pescetarian, but my diet is largely planted-based. I worked out I am eating about 50g/day protein.

        I had a look at Zone, and why it may cause high BG – but if it was a cortisol issue then I think I would be experiencing loss or muscle mass, possible weight gain etc, but I’m 14% body fat, and pretty strong, so I’m not convinced it is that. Interesting trying to work it out.

        • says

          I wasn’t referring to your cortisol;
          the zone diet says dietary protein raises your glucogon hormone levels
          which cause your liver to produce more glucose;
          you don’t need 50grams per day unless you’re doing major weightlifting work .

          • Janet Ruffin says

            PhT. – I believe that this is what occurs with me. If I eat more protein than 50, my morning FBS seems to be elevated (high 90’s to low 100’s). If I eat limted protein the day before, I have been getting FBS’s in the 80’s. I am finally getting to the bottom of this. I think I am very sensitive to carbs and protein. Too much protein is not what is needed for me.

    • sal bisslessi says

      Fasting and consuming high fat only gets very old. If I fasted as much as you did, I would be ripped to shreds.

      You never want to totally get rid of wholesome foods, like vegetables and fruits. I understand fruits have sugar, but eat small amounts.

      I seldom use ketosis. I like staying between 50-100 carbs per day.

      I like ketosis in theory but giving up my fruits, can’t do it. Wholesome nutritional foods have too many benefits for the human body.

      Ketosis is overrated. 100 grams and below should do you well. You need some carbs to keep your body to trigger bother energy sources fat and glycogen. Have the best for both worlds just do not blow out you cabs consumption. Works for me.

    • Gloria says

      I agree. And I think the problem is that we are using blood sugar levels to guage how our diabetes is doing–when we should have some way to measure insulin.

  16. Ben says

    Cortisol is a hormone that’s released when we are physically or mentally under stress (the body can not tell the difference between the two) the reason that blood sugar increases is because your body thinks you are about to be physically active. So it provides glucose for your muscles… Even if you aren’t going to use them

  17. Janet Ruffin says

    I find this very interesting. I believe that I am similar. If I don’t eat for a long period of time, my fasting BS is high 90’s to 110…. When I eat prior to going to bed, my fasting BS is better. I think I am going to have to do some more reading on this to get a better handle on this. I had no idea. Thanks everyone for sharing your stories.

  18. Aimee says

    Thanks for these fabulous posts! It is refreshing to hear some data from a practitioner who is NOT just pushing pharmaceutical solutions. I am attempting to lose weight low-carb style. I know I’ve been insulin resistant for years. After a week and a half averaging 14g of net carbs per day, I’m only losing a small amount of weight, and my blood sugar is hovering between 95-100 (fasting and after meals). Why would blood sugar remain so high, and why am I not seeming to stay in ketosis with heavy carb restriction? Thanks!

    • Janet Ruffin says

      I’m anxious to hear some responses as I am in the same boat as you. I don’t think I am as low as 14 for carbs each day…. that’s pretty incredible.

    • says

      . if 14g of carb hinder ketosis,
      consider less-glycemic carbs, eg, for 2 weeks
      try your only carbs are a soluble fiber supplement
      and remove conditions causing insulin resistance
      like caffeine, alchohol, other meds .
      if stress or lack of sleep is causing
      too much cortisol and not enough DHEA,
      do weightlifting or peak resistance isotonic exercises .

    • jh says

      moderately educated theory here:

      protein, especially in excess(high) amounts as in many low carb diets can undergo the gluconeogenesis pathway. If you were eating a traditional/standard american high carb and relatively frequent meal schedule prior to switching to low carb but high protein, perhaps the body is trying to do what it’s used to – using the enzymatic pathways that are ramped up – burn glucose for fuel. To get the body shifted to fat burning, we have to eat fat and moderate/adequate protein (approx under 100 g perday) and fasting should help with that, but it takes some time for the body to build up the fat/ketone burning enzymes. Apparently, I believe I heard in an interview with Tim Noakes, full ketoadaptation can take years.

  19. Kerrie Dolan says

    Hi Chris:
    This sounds like me! I’ve had reactive hypoglycemia for years. Now I’m dealing with post-menopause while on bio-identical hormones. Meanwhile, my fasting blood sugar is hovering around 100, my cholesterol is over 200 even on a statin & I just feel old & gross. I’m 51 & weigh 170. Yuck! I know eating my husband’s BLT, tuna melt or chicken parm w/ garlic bread along w/ several glasses of red wine on a Saturday night aren’t helping! I know I need to exercise but I feel so wiped out after work & a 40 minute drive. I also have a spouse & an 11 year old (which is great) but does take some time. Sorry this is so whiny but it’s been hard to find sound realistic diet & exercise advice for women my age! I’m having a hard time with sustained motivation! Thanks!

    • Gloria says

      I think it is very difficult to focus on personal habits and needs, when your life is focused on others. Getting healthy is about personal responsability –and that is not an easy thing to do when your life is oriented to responsability for others.

  20. c says

    hey everyone- i have a question. can anyone tell me why i get horrible hypoglycemia, weight gain, and just feel horrible when my cortisol is LOW? i have had cushings disease, and when my cortisol is high i immediately lose weight, feel wonderful, and my blood sugars normalize. this is the opposite of what should be happening. any advice is greatly appreciated. i recently had to have my adrenals removed because of the high cortisol- and the cure from cushings and the “low cortisol” has brought on serious weight gain, blood sugar issues, and pre diabetes. it is insane. any a dice is greatly appreciated.!

    • says

      if you felt great, why remove your adrenals? just kidding 😉
      too much cortisol is like too many pain killers …
      you feel great but you die young .
      . usually people who feel bad (as from low cortisol)
      abuse food — which would be the likely cause of your
      “serious weight gain, blood sugar issues, and pre diabetes.”
      . it’s not high cortisol that causes blood sugar instability;
      rather, insulin rebound from a glycemic (grainy sugary) diet
      (which mean having too high then too low of blood sugar)
      causes cortisol to be raised in order to
      protect the brain from low blood sugar
      (cortisol causes insulin resistance in the body
      so there is a guaranteed supply of sugar for the brain).

    • Rachel says

      From what I’ve learnt on my MSc in personalised Nutrition, when your blood sugar levels are low, your body needs to pump cortisol & adrenaline from your adrenals to raise your blood sugar levels, so if you can’t produce enough cortisol to do this, your BS will remain low. It also uses glucagon from your liver to turn glycogen into glucose but if glycogen is depleted through low carb diet then you won’t be able to increase your blood sugar that way either…just a thought

  21. Sonya says

    I didn’t hear any mention of time frame. Yes, glucose may temporarily be worse, but is blood pressure when you exercise. What matters is the long term benefit.

  22. Sky says

    Hi thee, Just got diabetes, eat no carb or sugar for 3 weeks now. My FBS was 283, now when I test myself in the morn it’s 220-240. As soon as I eat something it drops to like 178. & steady or drops more throughout the day to never as low as 173 so far. Still working on that. But my post meal never spike more then 20 points. Sometimes it only spike 2 points. I try to always snack & morning readings is still high. Fasting about 12 hrs. Please help. Any ideas? Or do I need to be patient, it’s been only 3 weeks. And am I lowering the numbers fast enough? Is hardly any post meal spike more important then the over all high number.? HELP!

    • says

      I believe waking up with high glucose
      is a sign of too much protein;
      get most calories from monounsaturates or mct oil,
      get a little fish oil, and cut back on vegetable oils (omega-6).
      . get most protein from raw yolks
      (Eggland’s Best or pastured eggs).
      . get carbs that increase insulin sensitivity
      like greens and brocolli . puree the hot greens in olive oil .
      take supplements that enhance metabolism:
      carnitine, alpha lipoic acid, Q10, mct oil .
      . if that wasn’t working for me,
      I would see my doctor for metformin (Glucophage).
      google this: metformin

      • Amy says

        PhT, who are you and what is your background/what are your credentials?

        You’re giving out a lot of advice here and IME not all of it is good.

        Be careful what you say to people.

        • says

          . I get the thread is about
          hyperglycemia due to high-stress cortisol;
          but if a person is still not getting results,
          then according to the zone diet’s Dr.Sears,
          high protein will raise your blood sugar levels .

    • Gloria says

      It takes longer than 3 weeks, and insulin levels, not transient blood sugar levels are what’s important. Blood sugar is just a down stream event. Hang in there and stick with the program.

  23. Stephen Gordon says

    In 2007 I was diagnosed with diabetes Type 2, cholesterol of 340, blood pressure 210 over 179. & a liver enzyme count that was headed straight for cancer. I was 57 years old, 5’8 & weighed 223 pounds.

    Luckily for me I spent a lot of time in hippie communes in the 60’s & i already knew a lot about diet & herbal medicine although I had obviously not been applying such knowledge.

    The day I was diagnosed I quit smoking & drinking. I refused all the poisonous meds that the doctors offered me & put myself on a basically vege diet & cut out all sugars hidden or otherwise. This eventually evolved into the Paleo diet which I have been on very strictly for the last 4 years.

    I also started exercising heavily. I had been an amateur boxer & long distance runner in my youth before everything start falling apart in my early 30’s. I started an intense program that has evolved to 2000 crunches 5 days a week, weight lifting twice a week & hitting the heavy bag for 3 sessions of 3 – 15 minute rounds a week. Plus a lot of floor exercise & stretching

    Lastly just under a year ago I took up a heavy intermittent fasting protocol: I eat once every day after fasting between 20 & 24 hours. The results of all this is that I’ve gone from 223 pounds to 142 (what I weighed at 21, I’m 64 now). My diabetes has been gone for over 5 years, I now have low blood pressure & cholesterol of 167.

    I have never felt stronger or had more endurance in my life. The point of writing all this is to let people know that it’s never too late to improve your health. Also, I was never a paragon of virtue & will power. If I can do this as messed up as I was, anybody can.

    Reading the article posted here & the comments got me to write all this as I have never posted on someone’s blog before but this is a terrific site with some great information!

    • Gloria says

      Stephen Gordon. Have you ever had a fasting blood sugar problem? I mean high fasting blood sugar?

      I agree with you, intermittent fasting is the best way to fix a diabetes/obesity problem.

  24. jen says

    I am newly diagnosed with diabetes type 2. I also have high blood pressure. I take nothing for the high blood pressure…and currently on metformin 500mg 1 time daily. When i had a random test two months ago my sugars were 256. Since then i have gone on a low carb diet/high protein. I eat about 25-30 grams of carbs a day. I also walk every day and ride my bike 5 miles every other day. I am 50 pounds overweight. The weight is coming off and the sugars are down dramatically. But not as far down as i would like to see them. My morning is usually around 106, eating walnuts before bedtime helps that. My after meal sugars are usually around 117 to 122 except for dinner which is usually under 140 unless i eat anything with starch- then it zooms near 160. I just cant seem to stop thinking that my morning sugars should be much lower and that i should be seeing more readings in the 90’s. But anytime im in the 90’s which is rare i feel really horrible. I have also noticed that when my period comes thdn my sugars go up no matter what i do and even if i have a simple cokd they also seem to rise a bit. I sleep 5-6 hours a night then nap in the daytime after work. Even on the weekends i cant sleep more than 7 hours. Im so worried that I’m killing myself and that something is very abnormal that even eating a half cup of low carb pasta would send my sugars soaring to 155! I’ve been told that things will get better after i lose more weight…but I’m truly scared about my fasting sugars and the fact that starches of any kind send me soaring. Im 47 and other than being overweight much of my life i dont have any serious health conditions…til now. Any suggestions or info would be really appreciated. Im thinking maybe fasting would help…but of course Im scared to try it.

  25. Joe Smith says

    Hello Mr. Kresser –

    The patients you mention are clearly clinically abnormal, and their results or experiences are not at all representative of those achievable by the general population.

    If conventional dieting strategies do not work for this particular set of patients, its hardly fair to malign IF for not working either.

  26. says

    Can you recommend some instructions re: how to use a glucometer to assess potential blood sugar issues? I’d like to know when I should test, and basic reference ranges.

    I recently began IFing as per PHD suggestions, but I’ve been eating low-carb for nearly four years and have also just begun introducing more “safe starches.” I am trying to understand whether these changes are making things better or worse!

    Much appreciation for this article, and the podcast I listened to today where Chris/Laura discussed various low-carb challenges and possible treatments!

  27. Julie says

    after reading all the comments i have a question: if i have become insulin resistant due to long term fasting and low carb diets- but am not in the pre diabetes stage as yet- is there any way that i can reverse this condition? because frankly, the thought of diabetes really scares me…

    • Ryan says

      I believe the answer is “yes, it is reversible”. From reading this post from Peter at Hyperlipid, there are different mechanisms behind what he refers to as physiological insulin resistance (what you experience on a low-carb diet) and pathological changes that causes diabetes.

      On a very low carb diet, your body makes your muscles and other tissues less insulin sensitive to spare glucose for those tissues that absolutely require it (brain, red blood cells, etc.). Once you start eating more carbs, your body will sense the higher availability of glucose and allow your muscles and other tissues to take it up.

  28. ambreen says

    okay, this is wierd. i have never had sugar issues before. infact, it almost always was on the lower edge. now suddenly my fasting blood sugar is in 90s. my bmi is good…. so is my blood pressure. my diet is fine as well…. no high carbs or high fats. my h1ac came back 5. last night before going to bed my sugar was 79. yet in the morning it was 96. i dont get it. my peak comes at about 90 minutes after a meal and it is in 120s. so i think my only problem is fasting blood sugar. any suggestions on what i should do now?

    • Michael says

      Hello Ambreen. I recently started IF and I am getting similar results you are. Post-prandial BS is below 85, I eat nothing of course since I am on a fast and take my BS in the morning and it’s 99. I don’t get it. Are you still having this issue or have you found a way out of this by manipulating your macros? Would really like to know. Thank you. — Michael, Tampa FL

  29. Lynn says

    I was going crazy with worry before finding this article. I eat low-carb and have been getting blood sugar readings in the 190’s post meals!
    I have been on a low-carb diet for 4 months (less than 25 grams per day). I work-out 45 minutes to an hour 6 days a week (alternating between kettlebells and recumbent bike).
    After a month of this diet and exercise routine (just recumbent bike at first), I bought a glucose meter (ReliOn) and started tracking my sugar levels. After a dinner of spinach salad and chicken and lime vinaigrette, I would consistently see readings of 135 mg/dl an hour after eating, but I wasn’t too worried and would lower the levels with a post meal workout. My morning fasting blood sugar has always been good (mid 80’s). After a 3 egg and cheese breakfast, my levels generally would rise to 115 and fall quickly. For lunch I’d have chicken and broccoli and see 135 an hour after eating. This was consistent for 3 months. I had couple of post-dinner readings in the 150’s, so I had an A1C test done at this point, and it came back normal. My fasting was also normal; my doctor wouldn’t perform the OGTT.
    Then, I started adding weight training to my workout routine via kettebells (love them). Additionally, I started intermittent fasting by skipping lunch at work. My afternoon blood sugar levels are in the low 70’s during this period. I drink one cup of coffee in the morning and another at noon. I eat my normal dinner of chicken and spinach, but now my blood sugar levels are in 190’s a half hour after eating and 170’s an hour after eating. This is not normal. I immediately go and workout to lower them back down, but I really am not eating carbs!
    After reading this, I think it may be attributed to cortisol imbalances from either overtraining or fasting or both. I have a heart condition (LQTS) that requires that I take a beta blocker, which can cause blood sugars to increase, too. But, I really think my issue may be cortisol. As much as I feel good on the afternoon fast between breakfast and dinner, I am going to try to have more frequent small meals or snacks (low-carb and high-protein) to see if I can fix these high blood sugar readings.

  30. rdzins says

    THANK YOU! I have been low carb for many years, and after listening to the mainstream of reducing calories, and intermittent fasting gospel, it is good for someone to come out and say hey that doesn’t work for everyone. I even gained weight by eating less and fasting. I am one of those people, the longer I go without eating the higher my numbers go. The problem was also that being I was eating low carb I really wasn’t hungry. Now I have to force myself to eat regularly, this does work for me and keeps my blood sugars below the 100 mark. It would be nice if there was more information out there on this. It is hard after years of being engrained on the the eat less theory that maybe we actually need to eat more.

  31. says

    Thanks for the useful information you are giving people who need to keep their blood glucose level normal. diabetes is a serious health condition and proper dieting is one crucial solution to keep it t bay.

  32. Peter says

    Prolonged fasting or severe calorie restriction causes elevated baseline levels of cortisol. This occurs in conjunction with depletion of liver glycogen, as cortisol speeds up DNG, which is necessary to maintain blood sugar in absence of dietary carbs, protein, or stored glycogen. It seems someone looked at what happens during starvation and took that to mean that short-term fasting is bad.

  33. Margaret says

    shredded you are misinformed. It is not a false reading. You have a high fasted glucose level because the low carb has made you insulin resistant. Low carb is bad news for a lot of people and you are one of them!

  34. shredded says

    I did IF and low carb for about 6 months. Prior to that, my fasting glucose was always in the low ’80s. I went for a test in December and it was 96. I freaked out, thinking I was becoming diabetic. Then I read on several sources that prolonged low carb can give you a high fasted glucose level. I’ve heard it’s not dangerous, it’s just a false reading, but it scared me enough to cut out fasting and eat more carbs. I might also add that I gained nearly 20 pounds doing IF and low carb…

  35. jana topinkova says

    I really need someone’s opinion on these hormonal isssues, eating low carb, and IF because I have had some very confusing contradictory experiences, and now I don’t know how and what to eat anymore.
    When I try eating high fat low carb diet tohether with IF (but even without), it always leads me to immediate fat loss (i am a woman with 21% body fat), high energy, glowing skin, no blood sugar issues, and just everything seems great. But after just a week or 10 days, I always encounter some unpleasant effects. Namely: hypoglicemia (for example the other day, after skipping dinner, I woke up with fasting glucose reading of 58, and so I ran for a sugar fix), i get very angry or anxious very often(as if my body is either trying to raise cortisol levels or maybe they re too high already…i dont really know how this works…), I d say it happens especially after a meal of protein and fat (I always eat vegetables, and i have often a glass of wine, so I am far from zero carbs). but it happens also in between meals. Another issue: night sweats and waking up around 3/4am each night (yet it doesnt make me tired). But I feel just very uncalm, I become obsessive, and it is rather a hell. Yet, when I complain, no believes I feel so crappy because it is during these periods that I look the fittest. So then I usually go back to eating pasta and bread, having breakfast. The symptoms disappear immediately. I become calm, I sleep normally, I always start to gain weight. I must absolutely eat 5 times a day food with carbs and protein to avoid shakiness from hypoglicemia. But overall, I certainly feel less energy burning all those carbs then when i have very little (I play tennis competitevily- so I notice immediately whrere my energy levels are). So if it wasnt for all those side effects, I would happily continue eating high fat-moderate protein-low carb. But it just doesnt seem sustainable for me. And having glucose of 58 is even rather dangerous I think. It is probably hormonal issues. When i eat paleo, i become so insulin sensitive that I think I realease too much insulin even just with a portion of fruit and some vegetables. And then the cortisol is obviosly there to raise the glucose to make up for thw catbs I didn’t eat….so I do t know what to do? Should I go back to my standard “balanced” diet of 3 meals (with starches), and snacks inbetween?

    • stephanie says

      I agree with everything you say!
      Why don’t you just eat good carbs like veggies. but still follow the protein/fat/carbs diet (but good carbs).
      I think cortisol is a big factor in all this and cortisol regulation is the factor in weather or not your body can handle fasting and low carb. I just don’t think the anxiety and side effects we get are worth it. It is too much stress on the body not eating any carbs. I think everything is so linked… it all gets so confusing!

  36. Stephanie says

    Also I think it would be worth me using a blood sugar monitor a testing which foods and what amounts keep my sugar levels in the healthy range. As I will do anything to keep those panic attacks away!! They are absolutely dreadful.

  37. Stephanie says

    Thank you for the article.
    I have hypoglycemia and pcos (hormone issues) and for a period of about 6 months I did fasting for about 20 hours 3-5 days a week. I felt great while doing it, lost a lot of weight! Although one day I started getting horrible panic attacks which I am still suffering from here and there to this day. I believe that it was the fasting, that put such a strain on my body and elevated cortisol levels. Do you agree with this? Right now I kind of follow a paleo, low carb, High protein kind of lifestyle… Thinking this is the best way to keep my hypoglycemia and panic attacks at bay- as they both go hand in hand. My naturopath/homeopath seems to think this is the best way.. Do you agree and what are your thoughts?

    I think fasting is great for those with no sugar imbalances- but I also know that fasting can lead to sugar imbalances! My hypoglycemia was unnoticeable till I started fasting… It was just something the doctor told me I had but I felt no affect from it prior to those months of fasting. So I think people should be careful before entering into fasting as it must elevate cortisol and put a lot of strain on the adrenals and other organs. Now if I feel I need to shed a kilo or two I just eat a very small protein breakfast such as an egg or a small can of tuna, and this really seems to work as eating less in the morning seems to make me less hungry for the rest of the day.
    Sorry for rambling but I would love your opinion!

    P.s just read your article on stress making you fat.. This couldn’t be truer. My body is in such harmony when I have inner peace. The weight seems to fall off no matter what I eat and food digests so easily!

  38. Andy says

    My blood sugar ranges from 84 to 125. Usually anytime I test it, it is around 115 to 125. I haven’t eaten for two days. My sugar began at 135 the evening I began fasting. It was 115 in the morning and 96 that night. It was 114 the next morning and 84 that night. What’s going on is that my liver dumps sugar into my blood in the early morning to fuel my body. I suspect my sugar will be in the 90s in the morning. I think it is important to get one’s sugar down below 85 part of each day – whether it’s before bedtime or when waking up in the morning. Below 85 is when the pancreas stops producing insulin constantly. If you don’t give your pancreas a rest it wears out over the years, and your diabetes gets worse. I need to lose about 15 pounds. I gained 10 over the past two months, and my blood sugar rose slightly as a result. I am beginning to believe that a low fat vegan diet is the way to go.

    • Gloria says

      I agree that a vegan diet is the way to go, since I myself have been mostly vegan for some 40 years. Vegan, low fat–no. Vegan plus moderate amounts of healthy fats–yes.

      I still get very high fasting blood sugars, though.

  39. Eggie says

    Thank you so much for this article. I started monitoring my glucose two weeks ago and my fasting blood sugar upon waking has never been under 100 – usually in the 110’s. Is this really a problem though? By lunch time, my first meal of the day, it’s back around the high 80s/low 90s.

  40. Susan says

    Would this also explain why glucose readings before going to bed can be lower or the same as when one rises (morning fasting numbers)? I have that problem. (note: I am still learning about this diet and have not implemented it; was following a dietician).

  41. Dave says

    Very informative article. I am following IF with pretty low carbs for weight-loss and despite having pretty low bodyfat, around 13%, I find my fasting blood sugar to be in the 90’s no matter when I test it, after 8 hours, 16 hours, or 16 hours + light cardio. The strange thing is, that even after a high-carb meal, blood sugar goes down to 82-83 or so, and stays there for a couple of hours.
    I have diabetes in my family and am worried I could make things worse with the current pattern of low carb IF + high carb refeeds 2x/weekly.
    I’d like to add in to Ryan’s question about carb/calorie levels during the normal meal pattern test period. Should I also switch to a moderate carb diet and near-maintenance level calories before I check for improvement?

  42. Ryan says

    Interesting post. This sounds like it could be the cause for my high fasting glucose. In addition to my high fasting glucose, my total cholesterol has been creeping up, to where it is now over 300 last time I had it checked. Could the high cholesterol level also be caused by excessive IF? I have been using daily IF for well over a year, sometimes one meal a day, along with heavy weight training 3-4 times a week.

    How long does it usually take to see improvement when switching from IF to several meals a day?

  43. jackie says

    is IF not recommended for people with adrenal fatigue? and what if you have cravings from neurotransmitter imbalances. i also have hormonal imbalances. in other words, should people who do not have optimal health be IFing at all?


  44. Sharon says

    Chris..thanks for this. Very interesting!
    I’ve been intermittent fasting since July 2011 using the Warrior Diet concepts. Big meal at night, undereating during the day, using whey concentrate and water before and after workouts, etc. I was only 116 lbs when I started and got to about 108.
    My post prandial numbers were fine and my AM Blood fasting numbers were low to mid 80s since I got my glucometer in November.
    For the past week, I have tested randomly in the mornings. I have been getting readings of 70, 73, 78 and today I got 65. This scared me a little.
    I’m wondering if it’s a good idea to go back to 3 meals a day..with some snacks.
    Also, I eat pretty low carb and have been for quite a long time. I’m adding a lot more fat than usual lately since the high fat/mod protein theory has come about.
    Any thoughts? Should I be worried about these low AM fasting numbers and what can I do to correct it?

  45. Mike Ellwood says

    This makes sense. I doubt if our ancestors would choose to go 12-14 hours without food if they didn’t have to. Fasting is a stressor, and cortisol is a stress relief hormone.

    How do we know that our ancestors didn’t take “snack” food with them on hunting expeditions? (e.g. dried meat or pemmican). I’m sure the more intelligent groups (i.e. the more adaptable and more resilient and the ones more likely to survive and propagate) would have done.

  46. says


    I also wanted to add something to my last post. Sometimes at night my blood sugar will feel low. I will check it and it will be in the 90’s. If I don’t eat anything, I will continue to wake up off and on and feel bad in the morning. If I do eat something then my numbers will be up higher when I check them in the morning. I really want to maintain good blood sugar control but short of not eating at all, I am not sure what to do.

  47. says

    I have been hypoglycemic since I was young. I had borderline gestational diabetes with one pregnancy and had gestational diabetes with another. My endocrinologist told me I was fine after my baby was born when I had a follow up appt. She said I wouldn’t have any problem as long as I continued to stay thin, which I am. A few years ago, I had a blood test for life insurance and saw that my A1c was 6.1 and my fasting was 78 so I knew there was a problem. I have been low carb since then but my fbs now is usually around 90-100. After a low carb meal, it usually stays under 120 but hangs around 98-105 2-3 hours after eating. It takes several hours for it to come down into the low 90’s or 80’s. Do you think eating every 2-3 hours would be helpful? I recently tried pgx for blood sugar control which kept my bs low but I think I had an allergic reaction because I was very itchy. Do you have any suggestions?

    • Amy says

      Cristie – Hi! I wonder what has transpired for you over the last few years since your post. I have had basically the exact same presentation of dysfunctional blood sugar regulation. I rarely run across someone whose story fits mine so closely. Would love to hear what has transpired and what you’ve learned. I wasn’t tested in my first pregnancy at age 31, and ended up very, very sick with HELLP Syndrome. I was borderline gestationally diabetic in my second and third pregnancies. I’ve considered myself “diet-controlled” pre-diabetic ever since. Basically, anyone who has gestational issues has underlying dysfunction and it’s just a matter of time, diet and lifestyle. My numbers have been on a gradual decline over the last 7 years since my first pregnancy despite my fitness, thinness and low carb high protein diet. These days I can’t get my fasting under low 100s no matter what I do. This morning it was 131 and I cried. Anyway, hope you are still getting the email follow-up for this post! Hope you are well!

      • Tara says

        Christie, Amy, are we all the same person? :) I don’t know if either of you are still reading this, but I have a very similar story. After gestational diabetes with my second baby, my blood sugars never returned to normal. I have a BMI of 20, I am fit, I have great cholesterol numbers, I eat a strict low-carb diet. It doesn’t make sense and my doctor has no explanation. For two years now I have been diet-controlled, with my a1c right around 5.6. But my fasting blood sugar, which always used to be normal, is creeping up now into the 90s. I’m just not sure what else I’m supposed to do.

        • says

          Add me as a 4th with the same issue. 😛 I also discovered prediabetes during pregnancy, have had to take out more and more carbs to keep blood sugars low and stable. And lately, they’ve crept up, too, where fasting is ~90 in the morning. It sometimes used to be 70! I’ve read about physiological insulin resistance from a low carb diet, but I don’t think that’s it. When I add carbs back, I feel awful, on that blood sugar roller coaster. I do only eat 3 low carb meals a day–meat, veggies, and coconut oil.

          • christina says

            Hi, me too. I had gestational diabetes with my second baby, however, it was gone after baby delivering. Last month my a1c test was 5.7! I am prediabetic, but fasting was 68! Then, since i cut almost carbs (sweets, noodle,rice…), my fasting increasing to 100!!!! two hours after one cup of soy milk in the moring, raising to 190!!!
            I have no idea…

  48. says

    you mentioned at front of the article that some IF’ers had high fast glucose, then, listed 90-100 as high? I always thought that was “acceptable”? I’d love to have a fasting glucose of under 100– haven’t had that since I was born.., I think? I was 120 fasting at one time, since have gotten down into the hundreds with IF, and just loosing wt. and healthy life.

  49. Cg says

    I have Crohn’s disease and have been interested in giving my gut more of a rest by intermittent fasting, just having an 8 hour feeding window, the Lean Gains approach. However, I’m flaring and am currently on prednisone, which I know raises your blood sugar and cortisol. Am I making things worse by intermittent fasting while on prednisone? Also, do you recommend IF for people with autoimmune diseases like Crohn’s, or are our adrenals probably too taxed to be doing something like this? What are your thoughts?

    • TV says

      Hey Cg,

      I, like you, are a crohn’s sufferer, and contemplating intermittent fasting for the reported healing benefits. Currently undergoing a flare as you were and i’d be very interested to know how you got on if you ultimately decided to go ahead with IF.



  50. Trevor Edmond says

    I’ve been searching long for a discussion on fasting and cortisol/cortisone levels.
    Several years ago I came across published results on the effects of fasting. This was publicised on (ABC Radio National – Health Report) and the Sydney Morning Herald.
    18 hours of fasting each day caused
    production of glucocorticosteroids sufficient to counteract inflammatory responses
    stimulates production of growth hormone
    strengthens the immune system
    With this regime I have managed to control (poly) arthritis in my body. I have a gouty arthritis condition. Stopping this regime brings on severe joint aches and pains within two or three weeks.
    Unfortunately I have developed type 2 diabetes. Together with a previous condition of sleep apnoea and a sleep requirement of 5 hours or less per day has precipitated a complex metabolic outcome for me.
    I continue to fast 16 to 18 hours a day. I feel all the better for it.

  51. Warthog says

    I have had “reactive hypoglycemia” for years, and had kept it under control by very careful staging of meals and snacks. My experience is that “intermittent fasting” works BETTER than such staging. I do IF three days a week (20 hours with an eating window of 4 hours). My blood sugar is MORE stable, I have MORE energy, and my mental clarity is better than on the days I eat normally.

    • chriskresser says

      That’s interesting. I suspect cortisol dysregulation is the x-factor which determines whether people do well or poorly on IF.

  52. Samantha Price says

    Perhaps the reason for the continued blood-sugar control issues in patients going paleo is rooted in under functioning adrenals. I have been following your blog for a awhile and I do not recall you ever addressing adrenal fatigue issues which are rampant in our super fast paced culture. I know that thyroid dysfunction is an area you specialize in and there are many hypothyroid patients that potentially have adrenal fatigue as well.

  53. chriskresser says

    Thanks for your comment, Paul.

    I think your last suggestion of including fiber and ensuring enough coconut oil during the fast is key. I can see that helping to balance the blood sugars and prevent cortisol – and thus glucose – spikes during the fast.

    It’s certainly an interesting topic and one well-worth exploring further.

    • mark says

      How is “taking coconut oil and fiber-rich foods like berries and leafy green vegetables during the fast” considered a fast?

  54. says

    Hi Chris,

    It’s a very interesting and complex topic, and great to hear your clinical experience.

    Fasting is a stress on the body, but it is normally a healing stress, because it stimulates cells to exercise metabolic pathways that are damaged in people with blood sugar control issues.

    Like resistance exercise, which is a stress that builds a stronger body, IF can be a stress that makes cells function better.

    So the fact that people don’t deal well with fasting doesn’t necessarily mean they shouldn’t do it. But it’s good to fix diet and nutrition first. A well-nourished body will get the most benefit and the least stress from fasting. (Thus, in our book, fasting comes in Step Four, the last step toward health.)

    In regard to high fasting blood glucose, one should also look at other causes — like very low carb intake. If people eat sufficient starches during their feeding period, fasting blood glucose shouldn’t be elevated by fasting.

    Also, taking coconut oil and fiber-rich foods like berries and leafy green vegetables during the fast can help reduce the stress of the fast, provide some benefits from ketosis, and improve gut flora.

  55. chriskresser says


    If you limit your snacks to high-fat, low-to-moderate protein choices, they shouldn’t spike your blood sugar/insulin so much. Eat just enough between meals to keep your blood sugar stable.

    Mike: sounds like a reasonable approach. Let us know how it goes.

    • says

      Hi Chris

      Great post. You mention “blood sugar issues” and irregular patterns, but what are the negative health effects of these? It seems to me that may people learn to live with that without ill effects.

      Look forward to your insights on this.

      Much appreciated,

      • says

        I have had issues with blood sugars for a year now. they drop low, 50-60 and I feel shaky and anxious.
        My fasting Insulin level was 12. I switched over to a paleo diet and now my fasting insulin is <2 (in june) and 4 now.
        My fasting blood sugar is between 83-86.
        My morning cortisol is 10.6
        I have gained 15lbs!
        Oh and my fructosamine is 283 (borderline high)
        my A1C is 5.
        something is not adding up.
        anyone have any ideas?

        I am eating 3-4 times a day and have a snack when I feel I need it, avacado or yogurt.

        typical day
        eggs with greens and pancetta
        decaf coffee with coconut oil/butter and tsp coconut sugar, oh and a bit of whole cream
        steak/chicken and vegetables and olives
        yogurt or goat cheese
        meat and veggies

        • armando says

          I am pretty sure you are not even counting calories it doesn’t matter whether you fast or not,it is all calories in calories out. Intermittent fasting is only good if you are trying to build muscle while gaining fat

  56. Deidre says

    Thanks. I may try it. I find eating to 3 times a day to be so much easier, plus grazing tends to get me into trouble. I definitely have reactive hypoglycemia, and I hated to see them up, so I figured if I minimized eating, even though my net carbs are usually under 30 per day, it would help. This is all very interesting, and there are so many differing points of view. I know that as long as I am paying attention and not following any advice from the ADA, I am much better off. Love your advice on this blog! Thanks again.

  57. Mike says

    Good points! I tried IF for muscular definition, etc, and it did not work initially. If anything, I felt like I had more stubborn belly fat. I am trying IF again now (“leangains” approach). I am careful to keep my (subjectively measured) cortisol levels down and to only IF when I feel like I’m not stressed. I minimize coffee, get adequate sleep, eat properly, then IF. The results seem to be better so far.

    Looking forward to future posts on the topic,

  58. chriskresser says

    It depends on your pattern. For people with reactive hypoglycemia, they have an overactive insulin response after eating a larger meal, and their blood sugar plummets. Then cortisol kicks in and raises it back up – but higher than it needs to go. This creates a “yo-yo” pattern throughout the day.

    You might try eating every 2-3 hours (small snacks between relatively smaller meals) and test your blood sugar throughout the day to see how that changes things.

  59. Deidre says

    Thanks for this post. This is me exactly. Paleo and very low carb, yet higher than I would like blood sugars. I have been trying to do 3 meals a day, thinking that if I didn’t eat snacks, I wouldn’t increase blood sugar post eating and release insulin and would be able to shed that last 10-15 pounds. Is my thinking wrong? I also recently started taking some herbs and cinnamon to try to bring it down.

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