RHR: Can You Reverse Your Biological Age?

In this episode we discuss:

• What biological age means and why biological-age tests can be misleading
• Why slowing aging is different from reversing aging
• How aging-related changes in muscle, strength, cognition, and physical function can be meaningfully improved
• The role of sleep, movement, nutrition, stress management, connection, and purpose in healthy aging
• Why foundational lifestyle habits should form the base of your longevity pyramid
• Where interventions such as sauna, cold exposure, red-light therapy, and other advanced tools fit into a sensible longevity strategy
• Which markers may be more actionable measures of healthy aging than a single biological-age score
• What the research says about multivitamins, omega-3s, spermidine, ergothioneine, and other emerging longevity compounds

Show notes:

• “Effects of cocoa extract and a multivitamin on cognitive function: A randomized clinical trial” by Baker, L.D., et al.
• “Prospective study of dietary mushroom intake and risk of mortality: Results from continuous National Health and Nutrition Examination Survey (NHANES) 2003–2014 and a meta-analysis” by Ba, D.M., et al.
• “DunedinPACE, a DNA methylation biomarker of the pace of aging” by Belsky, D.W., et al.
• “Individual and additive effects of vitamin D, omega-3 and exercise on DNA methylation clocks of biological aging in older adults from the DO-HEALTH trial” by Bischoff-Ferrari, H.A., et al.
• “Erythrocyte long-chain omega-3 fatty acid levels are inversely associated with mortality and with incident cardiovascular disease: The Framingham Heart Study” by Harris, W.S., et al.
• “Impact of healthy lifestyle factors on life expectancies in the US population” by Li, Y., et al.
• “Effect of multivitamin-mineral supplementation versus placebo on cognitive function: Results from the clinic subcohort of the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial and meta-analysis of 3 cognitive studies within COSMOS” by Vyas, C.M., et al.
• “Effect of long-term caloric restriction on DNA methylation measures of biological aging in healthy adults from the CALERIE trial” by Waziry, R., et al.
• “The effect of spermidine on memory performance in older adults at risk for dementia: A randomized controlled trial” by Wirth, M., et al.
• “Multivitamin supplementation improves memory in older adults: A randomized clinical trial” by Yeung, L.-K., et al.
• Learn more about the Bio-Avail Multi, Bio-Avail Omega+, or take our quiz to see which products best suit your needs
• If you’d like to ask a question for Chris to answer in a future episode, submit it here
• Follow Chris on Instagram or Facebook

Hey everybody, Chris Kresser here. Welcome to another episode of Revolution Health Radio. Today we’re going to talk about something that’s everywhere right now: biological age. You’ve probably seen it on social media. One of the newer blood testing companies like Function Health or Superpower gives you a number, and that number tells you how old your body “really” is according to them, regardless of what your birth certificate says. Maybe your chronological age is 52, but your biological age comes back at 46, and you feel great about it. Or it comes back at 58, and suddenly you’re spiraling.

There’s a whole industry built on this idea now. Test your biological age, buy the protocol, take the supplements, run the therapies, and watch the number drop. The promise is that you can reverse aging itself. I have a somewhat complicated relationship with all of this. I’m a functional medicine clinician, as many of you know, and I spent years helping people optimize their health at the deepest level. So I’m genuinely interested in the science of aging. But I’ve also watched a lot of health trends come and go, and I’ve learned to be skeptical when the marketing runs way ahead of the evidence. Before you think I’m here to tell you these tests are worthless, or that you can absolutely rewind the clock, I want to walk through what the research shows, because it’s more nuanced than either camp will admit.

Some of the best evidence we have comes from randomized controlled trials published in journals like Nature Aging, where researchers took the most advanced aging clocks and tested whether real interventions could move them. The results are humbling. They tell us that yes, you certainly can influence how fast you age, but the effects are smaller and messier than the biohacking world would have you believe. This matters because we’re in a moment where longevity has become a status symbol, and people are spending enormous amounts of money chasing exotic interventions while neglecting the boring fundamentals that overwhelmingly drive how well and how long we live. I don’t want you to waste your time or your money.

By the end of this episode, you’ll understand what biological age measures, why those clocks are less precise than they look, what the research says you can and can’t reverse, and where you should put your energy if you want to age well. Let’s dive in.

Let’s start with what biological age even means. The idea is simple and compelling. Two people can be the same chronological age, born the same year, but their bodies can be in very different shape. One 60-year-old has the arteries, muscle, and brain of someone a decade younger. Another has aged faster. Biological age is an attempt to capture that difference with a measurement instead of a guess. Most of these tests are built on something called epigenetic clocks. Your DNA sequence, the actual genetic code you were born with, doesn’t really change as you age. But the chemical marks sitting on top of it do. This is DNA methylation, small tags that attach to your DNA and help switch genes on and off, and the pattern of those tags shifts in fairly predictable ways over a lifetime. Scientists figured out that if you measure methylation at a few hundred specific sites, you can build an algorithm that estimates age surprisingly well across a population. The clocks have gone through generations, each one a little more sophisticated than the last. The first ones, like the original Horvath clock, simply tried to predict your chronological age from your methylation pattern. The next generation, with names like PhenoAge and GrimAge, went further and tried to predict health and mortality rather than just years lived. And the most recent versions don’t estimate how old you are at all; they estimate how fast you’re aging right now. One of the best known, called DunedinPACE, was described in a 2022 paper in eLife, and it was trained on people tracked across two full decades to capture the pace of biological aging in a single blood test. The idea is quite elegant. Instead of a snapshot of where you are, it’s more like a speedometer for how quickly you’re moving toward the end of the road.

That’s a genuine scientific achievement, and I don’t want to diminish it. These clocks are powerful research tools. Across thousands of people, they predict things that matter, like the risk of disease, disability, and death. But the single most important thing to understand about the number on your report is that these clocks were designed to be accurate across large groups of people, not to be precise for you as an individual. There’s an important difference. A tool can be excellent at showing that a population of fast agers has worse health outcomes, while still being shaky when you try to pin down one person’s number on a particular day. The researchers who built these clocks now know this, which is why the DunedinPACE team specifically engineered their measure to be more reliable, throwing out the methylation sites that gave inconsistent readings when the same blood sample was tested twice. That was a deliberate fix for a real problem because earlier clocks could give you meaningfully different numbers from the same person depending on the sample, the lab, or the day. Imagine stepping on a bathroom scale, then stepping on it a minute later, and getting a reading four pounds different. You’d probably stop trusting the scale. Some of the early clocks had that kind of wobble built in. So when your report tells you that you’re 46.2 instead of 52, that decimal point implies a precision that the underlying biology doesn’t really support, at least at this point.

None of this means the tests are useless. I’ve seen a real upside. In some cases, a biological age result genuinely motivates people to change. I’ve known folks who got a number back that was significantly higher than their chronological age, and that jolt was exactly what they needed to finally get serious about their sleep, their diet, their drinking, their movement. The number cut through years of denial in a way that a lecture from a clinician never could. If the test does that for you, it’s earned its cost. But notice what’s happening in that scenario: the value isn’t in the precision of the number; it’s in the behavior change it triggers. For most people, the result simply confirms what they already know. Someone who eats well, exercises, sleeps enough, and manages their stress is rarely shocked to see a lower biological age, and someone who’s been running themselves into the ground isn’t usually surprised to see a higher one. The test is often just an expensive mirror. That’s not worthless. Mirrors can be motivating, but it’s worth being clear-eyed about what you’re paying for.

This brings us to the biggest myth of all: the idea that you can completely reverse your biological age. The internet’s full of people claiming they knocked years off their clock with some protocol. The controlled research tells a more sober story. One of the most rigorous tests of this question came out of a trial called CALERIE, and the results were published in Nature Aging in 2023. Researchers took adults without obesity and randomized them to either cut their calories by 25 percent or to eat normally for two years. Then they ran several different aging clocks on their blood. Caloric restriction, which is one of the most studied longevity interventions in all of biology, did slow the pace of aging on the DunedinPACE clock. That’s a meaningful finding, and it supports the idea that aging is at least somewhat modifiable. But look closer, because two details get lost in the headlines. First, the effect was quite small. We’re not talking about turning back the clock a decade. We’re talking about modestly slowing the rate at which it ticks forward. Second, and this is the part almost nobody mentions, the intervention slowed one clock but did not significantly change the others, like PhenoAge and GrimAge. Same people, same blood, same two years of serious caloric restriction, and the different clocks disagreed about whether anything happened at all.

Biological age has become one of the hottest topics in the longevity world. But what does that number actually tell you—and can you really make yourself biologically younger? In this episode, Chris separates the promising science of aging research from the hype surrounding biological age testing and longevity hacks #ChrisKresser #longevity #aging

That really reframes the whole conversation. If the most powerful longevity intervention we know of produces only a small effect on one clock and no clear effect on the others, then the person online claiming they reversed their age by nine years is almost certainly seeing noise, regression to the mean, or the natural bounce of an imprecise measurement, not a genuine rewinding of their biology. Now, again, I don’t want to swing too far in the other direction because that would be its own kind of dishonesty. The pure skeptics get this part wrong. There’s a difference between reversing a number on the methylation clock and genuinely improving the hallmark signs of aging you can feel and function with. And in my years of clinical practice, I saw the second kind of change over and over. I worked with people who came in with real cognitive decline, the kind of brain fog and memory trouble that scared them, and by addressing the fundamentals, their nutrition, their sleep, their blood sugar, their movement, their function improved in ways that were obvious to them and their families. These weren’t people chasing a number on a report; they just wanted their minds back. And for many of them, the basics delivered.

I often saw the same thing with muscle, and this one is worth dwelling on because it’s so widely misunderstood. Muscle loss, what physiologists call sarcopenia, is one of the clearest markers of aging, and it’s often treated as an inevitable one-way decline. It isn’t. Skeletal muscle remains remarkably responsive to training throughout life. People in their 60s, 70s, and even their 80s can build measurable muscle and strength with consistent resistance training. This isn’t just about looking better or being able to open a jar. Muscle is metabolically active tissue that supports blood sugar regulation, bone density, balance, and independence as you age. When an 80-year-old gets stronger, they’re not slowing aging in the abstract. They’re reversing one of its most consequential physical signs, at least for a meaningful stretch of time. I watched it happen again and again, and it always struck me that something so effective is so often overlooked.

So my honest position is this: Can you rewind a cellular clock and become biologically younger in some deep, permanent sense? The evidence for that is weak. But can you significantly slow the pace of decline, and in some cases restore function you thought was gone, like cognition and muscle? Absolutely, and the research and the clinical experience both support it. Those are two very different claims, and the longevity industry blurs them together on purpose. Once you understand that distinction, the picture gets much clearer. The things that move the needle are remarkably boring, which is exactly why they don’t go viral.

A large study published in Circulation in 2018 followed more than 100,000 people for decades and looked at five basic low-risk habits: not smoking, staying at a healthy weight, moving your body for at least half hour a day, drinking only in moderation, and eating a reasonably good diet. That’s it. Nothing exotic. People who hit all five of those at age 50 lived, on average, 12 to 14 years longer than people who hit none of them. 12 to 14 years, from five habits your grandmother would recognize. No epigenetic test, no cold plunge, no rare peptide comes anywhere close to that kind of effect. That’s the frustrating irony at the center of the whole longevity conversation. The interventions with the strongest evidence are the ones nobody wants to sell you, because you can’t really put a premium price on “go to bed earlier and take a walk.”

I think about this as a pyramid. At the base, you have the true foundations: sleep, nutrition, movement, stress management, sunlight, connection, sense of purpose. These are unglamorous. They take real work and consistency, and they are overwhelmingly what determine your health span. Most people who are pouring money into the fancy stuff at the top are quietly neglecting this base, precisely because the base is harder to change than swiping a credit card for a new gadget.

I want to linger on the base for a moment, because people nod along when I say sleep and movement, and then completely underestimate how much leverage is there. Sleep is the clearest example. When you’re chronically shorting yourself on sleep, you’re impairing glucose metabolism, appetite regulation, memory consolidation, immune function, and the brain’s overnight cleanup process all at once. There is no supplement, no peptide, and no red light panel that compensates for years of five-hour nights. Movement is similar. A body that sits for 10 hours a day is sending a very different set of signals than one that walks, lifts, and moves throughout the day, and those signals reach nearly every system you care about. This is what makes the foundations so powerful. They’re not single-target interventions. They’re upstream of everything.

On top of that foundation, there’s a layer of what I’d call pleiotropic interventions. Things that hit many systems at once and most people will benefit from. Deliberate heat and cold exposure fits here. Regular sauna use, for instance, has been associated with better cardiovascular and brain health outcomes, and cold exposure appears to nudge metabolism and resilience in useful ways. So does smart supplementation, which I’ll come back to in a moment. These aren’t hacks that replace the basics, they’re multipliers that work when the basics are already in place. Layered on top of good sleep and consistent movement, they can push you further. Layered on top of a broken foundation, they mostly just drain your wallet.

At the very top of the pyramid, you have advanced tools everyone loves to talk about: photobiomodulation, or red light therapy, pulsed electromagnetic field devices, various regenerative therapies. I’m not against any of these, and in fact, I use most of them myself. But they belong at the top for a reason. If your sleep is a mess and you’re not moving your body, buying a red light panel is like putting a spoiler on a car with no engine.

If you do want to track your own aging with something more actionable than a methylation number, there’s a better approach, and it’s mostly free. Track the markers that are both meaningful and modifiable. Your grip strength and how many times you can stand up from a chair in 30 seconds tell you a lot about muscle and function. Your VO2 max, which you can estimate from a hard walk or a run, is one of the strongest predictors of longevity we have. Your waist circumference, your resting heart rate, your blood pressure, and standard blood markers like fasting glucose, triglycerides, and your omega-3 level round out the picture. Unlike a biological age report, every one of these responds to the work you put in, and you can watch them improve month over month. That feedback loop is worth more than any single number a lab can hand you.

Let’s talk a bit more about that supplementation layer. The most valuable role supplements play, again, isn’t some exotic anti-aging effect. It’s shoring up the nutritional basics that a huge percentage of people are falling short on. Take the humble multivitamin, which the longevity influencers tend to sneer at as too basic to matter. Before you dismiss it too, consider how common nutrient gaps really are. National survey data consistently show that large fractions of the population fall short on magnesium, vitamin D, vitamin K, choline, and many other essentials. Even people who consider themselves healthy eaters. Modern soil depletion, refined foods, and the simple reality of busy lives all conspire to leave gaps. A multivitamin doesn’t turn a poor diet into a good one, and it was never meant to. What it can do is provide a nutritional floor, so that the raw materials your body needs to build neurotransmitters, repair tissue, and run its metabolic machinery are consistently available. That’s a modest, sensible goal, and it’s exactly the kind of unglamorous move that pays off over decades.

The COSMOS trial, one of the largest studies of its kind, put the multivitamin assumption to the test. In one arm published in Alzheimer’s and Dementia in 2022, older adults took a daily multivitamin and multimineral or a placebo for three years, and the multivitamin multimineral group showed better global cognition. A separate arm published in the American Journal of Clinical Nutrition in 2023 found a memory benefit equivalent to about three years of age-related change. When researchers pooled the COSMOS cognitive studies together, the benefit on overall cognition held up, roughly the equivalent of reducing cognitive aging by a couple of years. That’s from a daily multivitamin, and frankly, not even a great one. It’s not flashy, but it’s real, replicated, and cheap.

Omega-3 fatty acids are another one worth your attention, and here the aging research is especially interesting. A 2025 study in Nature Aging, drawing on a trial called DO-HEALTH, tested vitamin D, omega-3s, and exercise on those same DNA methylation aging clocks. Omega-3s on their own slowed several of the clocks, and when you combined omega-3s, vitamin D, and exercise, the effects added up. The effect sizes were small, in keeping with everything else we’ve discussed, but the direction was consistent. When you zoom out to hard outcomes, a 2018 analysis from the Framingham Heart Study, published in the Journal of Clinical Lipidology found that people with the highest levels of omega-3s in their blood had roughly a third lower risk of dying from any cause compared to those with the lowest levels. That’s the kind of endpoint that really matters.

There are trendier longevity molecules that biohackers get excited about, and a few of them do have legitimate research behind them. And I’m quite interested in these nutrients and take some of them myself, and follow the research on them carefully. Spermidine is one. A small 2018 trial in Cortex found that older adults at risk for memory decline who took a spermidine-rich supplement showed modestly better memory performance than those on placebo. Ergothioneine is another, an antioxidant found in its highest concentration in mushrooms. A 2021 analysis in Nutrition Journal pooling several cohorts found that higher mushroom consumption, the richest dietary source of ergothioneine, was associated with the lower risk of dying from any cause. Others, like fisetin and pterostilbene, are genuinely promising but still in the earlier research process, with most of the compelling data coming from animal and lab studies rather than larger human trials. So these compounds are definitely worth watching, and some are worth taking, in my opinion. But notice where they sit on the pyramid. They are a layer on top of a solid foundation, not a substitute for it. If you’re taking spermidine but sleeping five hours a night, you’ve got your priorities backward. I’d gently point out that the money people spend on a rotating cabinet of exotic longevity compounds, peptides, etc. would, in many cases, be far better spent on a good mattress, a standing desk, a gym membership, or simply better food. The math on that trade almost always favors the basics.

Which brings me to what you should do with all this information. If there’s one action step I’d give you, it’s this: don’t try to overhaul everything at once, and don’t start at the top of the pyramid. Instead, take an honest look at your foundations and identify the weakest one. For a lot of people, it’s sleep, and you probably already know if that’s you. For others, it could be a diet built around processed convenience food, or a body that barely moves during the day, or chronic unmanaged stress that never gets a release valve, or life that’s become quietly disconnected from other people. You usually don’t need a test to tell you which one it is. If you sit quietly and ask yourself where the biggest gap is, the answer tends to surface pretty quickly. Pick that weakest link and start there. Just one. Give it a few weeks until it’s a stable habit that doesn’t require white knuckle willpower anymore, and then move on to the next one. Build some momentum, let each change reinforce the next, and work your way up the pyramid rather than down from the top. This sequencing matters more than people think, because trying to fix everything at once is how most people end up fixing nothing. That approach is far less exciting than getting a printout that tells you you’re biologically 46 when you’re 56. There’s no dashboard, no trend line, no gadget. But it’s the one that works, and it’s the one I’d stake my reputation on.

Before we wrap up, I want to mention two of the foundational supplements I formulated, because they map directly onto what we’ve just covered. When I built the Bio-Avail line, my goal wasn’t chasing anti-aging compounds. It was supporting the nutritional basics as well as possible, since that’s where most people have the biggest gaps. Bio-Avail Multi is a comprehensive multivitamin, multimineral, and phytonutrient blend designed to fill those everyday nutrient shortfalls, the kind the COSMOS research suggests can help support healthy cognitive function as we age. Bio-Avail Omega+ delivers a meaningful dose of EPA and DHA in a highly absorbable form to help maintain healthy omega-3 levels, which support brain, heart, and healthy aging. It also contains curcumin and black seed oil, which have longevity benefits as well. Neither of these is a magic bullet, and I’d never present them that way. They’re there to reinforce the base of the pyramid, so the rest of your efforts have something solid to stand on. You can find both at AdaptNaturals.com if you want to learn more.

Here’s what I keep coming back to: the longevity industry has been very good at selling us the top of the pyramid because the base can’t be patented, packaged, or marked up. But the number on a report was never the point. The point is the life you’re living underneath. Take care of the foundations, and the years will take care of themselves.

Thanks for listening. You can find show notes and links to all the studies I mentioned at ChrisKresser.com. If you have questions about this episode or suggestions for future topics, head over to ChrisKresser.com/podcastquestion and leave me a message. I read all of them, and your questions help shape the content I create. Until next time, be well.