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Is a Low-Carb Diet Ruining Your Health?

by Laura Beth Schoenfeld, RD

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Carbohydrates, and the role they play in a healthy diet, are one of the most hotly contested nutritional debates in the world, both in conventional and ancestral health circles.

One one side, you’ve got folks who say that carbohydrates are nonessential and increase your risk for diseases such as diabetes, cancer, and neurological disorders. On the other side, some say that carbohydrates are crucial for good health and should make up the majority of your calories.

It’s no wonder I have so many clients who come to me completely confused about carbs and whether or not they should eat more or less of them.

While some people do incredibly well following a low carb Paleo diet, there are many people who crash and burn on this type of dietary plan. So, how can you tell if you’re the type of person who shouldn’t be eating a low carb diet, and how do you figure out how many carbs you should be eating? I plan to teach you just that in this article.

Is your low-carb diet doing you more harm than good? Find out how many carbs YOU should be eating.


I recently discussed the role of carbohydrates during pregnancy in an episode of The Ancestral RDs Podcast. The most important reason why women need adequate carbohydrates during pregnancy is to ensure adequate fetal brain development and growth. Another reason is because a high protein diet can be dangerous during pregnancy, and when you cut out carbohydrate as a major macronutrient, you usually can’t help but increase protein as a percentage of calories. Protein intake greater than 25% of calories during pregnancy may lead to decreased mass at birth and increased perinatal morbidity and mortality for the baby.

The Institute of Medicine recommends a minimum of 175 grams of carbohydrates per day during pregnancy, which is 29% of calories on a 2400 calorie diet. Paul Jaminet advises pregnant mothers to restrict protein to about 15% of calories and to obtain 30% of calories as carbohydrates. Chris recommends a moderate carb approach for most pregnant women (except those with any type of diabetes) in his book, Your Personal Paleo Code (published in paperback as The Paleo Cure in December 2014).

Like these other experts, I generally recommend 30% of calories from carbohydrates for my pregnant clients, and also for those who are struggling with fertility. Unless you have diabetes or a serious neurological condition that requires carbohydrate restriction, it’s not worth the risk playing around with a low carb diet when you’re pregnant, and these diets aren’t conducive to fertility for many women either. (If you’re interested in more reasons why carbohydrates can affect fertility, read this great post by Stefani Ruper.)


If you’re a professional or recreational athlete who trains hard 4, 5, or even 6 days per week (I hope you’re not doing 7 days per week!) and trying to maintain this level of activity on a low carb diet, you may be doing more harm than good to your health and fitness.

While there are athletes who thrive on a well-planned low carb approach (LeBron James most recently!), there are many others who do not. Each athlete is completely unique in their ability to perform well on a low carb diet, and there’s nothing wrong with testing out the diet to see how it affects your athletic ability.

But if you’ve been trying a low carb diet for months now and your workouts are suffering, your weight isn’t budging (or maybe you’ve even gained weight!), and your recovery time is increasing, you’re probably not the type of person who can handle a low carb diet combined with regular intense physical activity.

I’ve had many clients come to me on a low carb diet who, after switching to a more moderate carb approach, found that their energy and endurance significantly increased, and they were able to make quicker strength gains than before. Many also were able to shed some of the stubborn body fat that they’d been retaining despite eating a low carb diet and training hard, which was a result they didn’t expect!

For my athletic clients, I usually recommend a minimum of 20% of calories from carbohydrate, and depending on the person’s health goals, training schedule, and current issues, I may actually recommend more like 40-50% of calories from carbs.

Again, each athlete is an individual and what works for one person, or even a thousand people, may not work for you. So don’t be afraid to experiment and pay attention to how your diet makes you look, feel, and perform! And don’t hesitate to get help if you need it!

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Hypothyroidism and HPA Axis Dysregulation (Adrenal Fatigue)

Hypothyroidism is one of the most commonly cited medical reasons for needing to eat a moderate carb diet. The main reason why carbs affect thyroid function so directly is because insulin is needed for the conversion of the inactive T4 hormone into the active T3 hormone, and insulin is generally quite low on very low carbohydrate diets.

So if you’ve suddenly started developing hypothyroid symptoms on your low carb diet, it’s a pretty good sign that you’d be better off upping the carbs (and getting your thyroid tested if you haven’t already!) For more about how low carb dieting affects your thyroid, listen to this great interview with Chris by Jimmy Moore.

HPA axis dysregulation, also known as adrenal fatigue, is another condition where a moderate carb intake is important for general health. Kelsey and I talked about adrenal fatigue on our first Ask the RD podcast, so listen to it if you’re unfamiliar with this condition. The main hormone that gets dysregulated in adrenal fatigue is cortisol, and cortisol has been shown to increase on a low carb diet. This means that a low carb diet is a potential adrenal stressor in susceptible individuals. Combine that with a stressful job, inadequate sleep, and overexercise, and you’ve got yourself a recipe for adrenal burnout.

So if you have adrenal fatigue, or if your current lifestyle is already high stress in a few different areas, you may want to increase your carb intake until you can get those additional stressors under control, as you may drive yourself into adrenal fatigue by having a chronically elevated cortisol output. Lara Briden has written a great article on the benefits of whole food carbohydrates in lowering cortisol and raising GABA, a calming hormone that is often low in adrenal fatigue patients.

If you’re experiencing symptoms of hypothyroidism or adrenal fatigue, you may be worsening them with a well-intentioned low carb Paleo diet. I recommend working with someone to help you figure out if your diet is indeed making these symptoms worse, and how to change what you eat to better support your thyroid and adrenal health.

Gut Health

One of the less discussed downsides of a very low carbohydrate diet over the long run is the potential for alteration of the gut flora. Chris recently covered this issue in a podcast with Jeff Leach, where they discussed evidence that a very low carb diet can lead to gut dysbiosis and a reduction in the diversity of the gut flora. A lot of the information on this topic is new and not fully understood, but it’s reasonable to believe that when you avoid carbs, you’re also avoiding important prebiotics (i.e. food for your gut flora) like soluble fiber and resistant starch.

These prebiotics are essential for promoting the growth of beneficial gut flora. Without them, your beneficial flora can’t produce as much gut-healing substances like butyrate and other short chain fatty acids, and your microbiome composition may even shift in an undesirable direction. And as Chris would say, you’re only as healthy as your gut is: an unhealthy gut contributes to everything from obesity and diabetes, to digestive illness, to autoimmune disease, to skin disorders.

Those who are doing very low carbohydrate diets, and who simply can’t increase their starch intake for whatever reason, should use prebiotic supplements such as resistant starch-rich unmodified potato starch or FOS powder. However, these products must be incorporated slowly into your supplement regimen, as you can experience severe gas and bloating if too many prebiotics are taken all at once, or if there is existing gut dysbiosis or bacterial overgrowth. In this case, it would be wise to work with someone who can help you get the prebiotics you need while on a very low carbohydrate or ketogenic diet to protect the health of your gut microbiota.

How Many Carbs Do I Need?

To determine how many carbs my clients need to eat in a day to reach their health goals, first I decide what percentage of calories from carbs they’d possibly do best with. As an example from above, a woman struggling with fertility issues may benefit from a carb intake around 30% of calories. I then determine her caloric needs using a calculator like this one. If we determine that her daily needs are roughly 2000 calories per day, 30% of calories from carbs is 600 calories. As there are 4 calories in a gram of carbohydrate, this works out to be 150 grams of carbs per day.

Usually I give my clients a target range to hit depending on their activity levels, and we use these targets to re-evaluate their food diaries and see if they’re hitting their goals. Most of my clients are surprised to learn how much carb-rich Paleo foods they have to eat to get up to 150-200 grams per day! But once they start making a real effort to hit those targets, the health benefits are immediate.

These benefits include weight loss, elevated mood, skin improvements, increased energy, normal menstrual function, more satisfying sleep, and more. It’s so exciting to see what a couple of starchy tubers and pieces of fruit can do for a person’s health when they simply need to eat more carbs!

Final Thoughts

The purpose of this article was not to bash low carb diets. I truly believe that there are many people out there who get amazing health results from a low carb plan, and there are dozens of health conditions that benefit from a very low carb or ketogenic diet, especially severe neurological conditions. Paul Jaminet has written some great posts explaining when a ketogenic diet may be useful and necessary, so I strongly suggest reading those posts if you’re still on the fence about where you stand with carbohydrates and your health needs.

My hope is that by reading this article, you’ll be able to understand the many factors that play into how a person handles a low carbohydrate diet, and whether or not their health will improve on such a plan. Everyone is different in their ability to thrive on a low carbohydrate diet. If you’ve found yourself identifying with any of the issues I’ve written about in this post, you may be in need of a macronutrient adjustment in your diet.

Helping people optimize their carb intake is a challenge I truly enjoy. As a dietitian, I love to help people evaluate their diet to determine if they’re meeting their health needs with the food they’re eating. If you think you could benefit from a Paleo diet makeover, I’d love to chat with you about where you’re at and where you want to go with your health.

Your carb intake shouldn’t be the major factor that’s preventing you from reaching your health goals. I hope you use the information I’ve shared today to evaluate your own nutritional needs and make the changes that make sense to you.

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Laura Beth Schoenfeld, RD
Laura Beth Schoenfeld, RD

Laura Schoenfeld, MPH, RD, is a licensed registered dietitian and women’s health expert trained in Functional Medical nutrition therapy. She assisted in the creation of educational materials for both the ADAPT practitioner and health coach training programs.

Her passion is empowering women to nourish their bodies, develop true strength, and ultimately use their improved health to pursue their purpose. Laura guides her clients in identifying and implementing diet and lifestyle changes that allow them to live a healthy, fit, symptom-free life without being consumed by thoughts of food and exercise. She draws from a variety of sources to form her philosophy on nutrition, including ancestral diets, principles of biochemistry, current research, and clinical experience. Her areas of expertise include women’s hormones and fertility, gut health, autoimmune disease, athletic performance, stress management, skin health, and weight loss. Recognizing that health goes far beyond just diet and exercise, Laura teaches her clients how to focus on and implement life-changing mental and spiritual health habits as well, including changing their thoughts and beliefs to ones that drive health-supporting decision-making around food, fitness, and life in general.

Her greatest mission is to help health-conscious women realize that, while their health is priceless, they are so much more than a body. When she’s not educating and serving her coaching clients and community, Laura loves traveling with her husband, Sundays with her church family, hikes with her dog, beach trips, live music, and strength training.

Professional website: lauraschoenfeldrd.com

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Join the conversation

  1. Thank you so much for your contribution to this topic! I’m a 35 year old female and I’ve been Euthyroid Hashimoto’s since 1997. After a period of severe stress last fall, I went into adrenal fatigue, vitamin D deficiency (17) had a surge in thyroid antibodies (tested 2/1/17) which led my functional medicine doctor to start me on AIP for 60 days, adrenal support supplements and 50,000 IU of Vitamin D for 30 days beginning 3/25/17. I’ve seen an increase in energy and emotional stability, and have lost 7 lbs (I’m 5’8 and was only 108 lbs to begin with so we’re watching it closely) I’ve been able to successfully reintroduce eggs, almonds, coffee, brown rice and ghee.

    I just received my 2nd set of lab results from 6/13 and was shocked to see my TSH enter hypo territory for the first time in 20 years (6.68 on 6/13 compared to 3.32 on 2/11) My antibodies have decreased negligibly. My Vitamin D has jumped to 105 after the thirty days of D3.

    It’s hard not to think my protocol over the past 80 days doesn’t have something to do with the TSH, so I began searching and found your explanation of the potential effects of low carbohydrates and hypo/adrenal fatigue.

    I’d be so grateful for your input on my situation. My instinct at this point is to reintroduce other non-gluten grains to increase my carbohydrate intake. Any other suggestions?

  2. My energy crashed badly after going into ketosis, with exhausted adrenals and thyroid meds not working with the efficacy that they did and experiencing terrible hypoglycemia. Low carb is not for me.

    Thank you for this article, it’s helped me understand why my body cannot function on no carbs.

    Back to the carbs……yum! 🙂

  3. Thanks for the article, it illustrates very wll my experience, which is 100% as you describe, since keto-enthousiasm on the web can make you miss the point that everyone is different and continue to make wrong. After 1 year of low carb (50-80gr/day) which combined with a lot of exercise made me lose 20kg (and gain some muscle), I started to feel exhausted. So increased protein even with supplements I had not used before, but it got worse. I added some carbs but they probably were not enough and not the right ones for my body (beans for instance, they don’t make me feel energized, basmati rice or potatoes do), I hit a plateu so convinced my self to go full ketosis. It was quite easy at beginning, my body was accustomed to low carb but nevertheless the first week with low veggy and <30gr/day was quite hard, then second and third was ok and even nice (no hunger), but after that it was a progressive crash down up to 4 months of keto adaptation (measured). Energy went down, I could make just a bit of exercise probably thanks to the fitness I had accomplished before but it was like a car using the last fuel, it got worse day by day. Then some bad things happened: cold body temperature (even 35°), panic and insomnia, even lower energy and feeling sick even if I used to eat lot of good fats (avocado, coconut, olive olil etc). I added grey salt and magnesium, followed all the tips by keto-gurus (!), my body got exhausted, fasting blood glucose increased from 70 to 90, colesterol increased (LDL too), body pressure was (is still) quite low. I think I messed with my thyroid. I started reintroduce carbs I tolerate well, such as basmati rice and potatoes and they made the magic. For instance after a carb meal my body temperature increases upt to the norm (36,6°C) but not if I don't eat carbs. Must add that I follow an intermittent fasting every day, which I had to interrupt during the pure keto diet (4 months, no recharges). It seems that only if I eat some carbs at the evening than feel energized the morning after and have no wish for food. It results as a natural aproach to fast if I eat some carbs, otherwise I need to always eat. I just think my body can't do it without a bit of carbs, and if I don't the consequences are quite hard. I felt like crap and almost got to the hospital, so no more keto for me, at least not without (many) carb-up days

    • Wow. I have been eating clean and exercising, in my opinion, moderately for 10 weeks now (about 4-5 this mes a week). The last couple of weeks my muscles really suffered more than usual. It became intolerable finally so much that I I decided to take time off from exercising. Originally it was going on o be a few days but ended up one week. I did feel the inflammation going down significantly in my legs but the exhaustion was terrible. All I want d to do was sleep. And then I had a small toast plate of spaghetti with meat sauce. Within minutes quite literally, I felt like I drank copious amounts of energy drinks. It has remained that way the rest of the day. I feel like I was starving myself of carbs. I felt my fatigue and brain fog lift after I ate the glorious toast plate of spaghetti. Anyone else ever feel this way?

  4. I can´t tolerate carbs anymore and have them cut out for longer than 6 months. I have substituted this through eating a smoothie with 1 cup of blueberries and 2 bananas in the morning, and one in the evening. But now i begin to have a intolerance against fructose, and i don´t know what to do anymore. Im from Germany and don´t have the money to go to a Functional Neurologist.

    • Use an app like my fitness pal to see how many carbs are in what you eat. Sayying you are eating a low carb diet, but you are having 4 bananas a day doesnt add up. 1 banana has 29g of carbs and 4 fiber = 25 net carbs each toal of 100g of carbs = 400 calories. And on a 2500 cal diet you are at 16% carbs just from the bananas.