Your birth certificate says you are fifty, but a blood test may give another number: forty-eight or fifty-four. “Biological age” has become the main promise of the longevity market in recent years, and every exercise or diet claims to take some years off our biological clock.
The question of this article is what the evidence actually says. The short answer: associations are visible, but most are observational, and the claim of “several years younger in a few weeks” runs ahead of the evidence. Below I give the numbers, sources and limits of each study.
Chronological age is just a count of years, whereas biological age tries to gauge the real state of the tissues. The most common research tool is the “epigenetic clock”: the DNA methylation pattern in a blood or tissue sample is read, and models such as Horvath, Hannum, PhenoAge and GrimAge convert it into an “age.” The gap between this age and chronological age is called “epigenetic age acceleration.” Another model, DunedinPACE, measures the “pace of aging” rather than age itself.
Chronological age is one number and daily habits are another; research tries to measure the gap between them — Image: AI-generated / Gemini 3.1 Flash via OpenRouter
The key point is that these clocks are still research tools. As the next section shows, in a single study exercise was significantly linked to some clocks and not to others. So the number from a commercial test of “my biological age” should be read as approximate, not as a firm verdict on the body.
Does Exercise Really Turn Back the Biological Clock?
A recent systematic review and meta-analysis in Lancet Healthy Longevity (2026) examined 44 studies with 145,465 participants. Overall, higher physical activity was associated with lower biological age, but many associations did not reach statistical significance. In the meta-analysis of seven cross-sectional studies, each one standard deviation of higher activity was linked to 0.03 SD lower Horvath acceleration and 0.09 SD lower GrimAge acceleration. No significant association was seen for Hannum or PhenoAge.
These effects are small, and the authors stress that the evidence is mostly cross-sectional which limits causal inference. Healthier people may simply exercise more, rather than exercise having made them younger.
For strength training the evidence is of a different kind: not epigenetic age, but mortality and disease. A meta-analysis of 16 cohort studies in the British Journal of Sports Medicine (2022) linked muscle-strengthening activities to a 10–17% lower risk of all-cause mortality, cardiovascular disease, total cancer, diabetes and lung cancer. The association was J-shaped: for all-cause mortality, cardiovascular disease and total cancer, the largest risk reduction, about 10–20%, was at roughly 30–60 minutes per week, and the effect of higher volumes was unclear. This too is an observational association, not proof of causation.
The popular claim that “90 minutes of strength training a week takes four years off biological age” was not found in the sources I reviewed for this article [needs further verification].
What Role Does Diet Play?
The Stanford identical-twin trial is cited often. Twenty-two twin pairs (mean age 39.6 years, 77% women) followed a healthy vegan or a healthy omnivorous diet for eight weeks. In JAMA Network Open (2023) the vegan twins, compared with their omnivorous co-twins, had a 13.9 mg/dL greater drop in LDL, a 2.9 μIU/mL greater drop in fasting insulin and 1.9 kg greater weight loss. But the primary outcome was LDL and the secondary outcomes were other cardiometabolic risk factors, and “biological age” is not reported in its abstract.
A systematic review of 21 intervention studies in Frontiers in Aging (2024) gives a more cautious picture. Of four studies on healthy dietary patterns, two were linked to lower epigenetic age acceleration, one showed an increase in global methylation and one found no effect. The authors explicitly write that larger randomized trials are needed.
The most recent example is a pilot study in GeroScience (2026). Thirty-four adults aged 48 to 81 with metabolic syndrome consumed one ounce of tree nuts (about 28 grams) and two tablespoons of extra virgin olive oil daily for four weeks. Adherence exceeded 95%, but no significant change was seen in DunedinPACE or AgeAccelGrim. The study was designed to test feasibility, not to prove or refute an effect.
Why Are We So Eager to Stay Young?
Psychoanalysis adds another layer to this question. In “Thoughts for the Times on War and Death” (1915), Freud writes that our unconscious does not believe in its own death. On this basis, the obsession with a biological-age number can be read as an attempt to master something the mind cannot picture: finitude. Freud’s insight explains why a single number can carry so much psychological weight.
The practical consequence is simple. A number from a test can create false reassurance or fresh anxiety. If we exercise and eat well for a better life today, and not to bargain with a number, it fits the evidence better and is less tempting to obsess over.
Does 90 minutes of strength training a week take four years off biological age?
I did not find such a figure in the sources reviewed for this article [needs further verification]. What is documented is that 30 to 60 minutes a week of muscle-strengthening activity was linked to 10–20% lower mortality risk in cohort studies; an association, not proof of causation.
Does a vegan diet lower biological age?
In the identical-twin trial, a healthy vegan diet over eight weeks lowered LDL, fasting insulin and body weight compared with a healthy omnivorous diet. Biological age was not reported in its abstract. So it has evidence for cardiometabolic risk factors, not for “rejuvenating” epigenetic clocks.
How reliable are commercial biological-age tests?
Different clocks do not give the same answer: physical activity was significantly linked to Horvath and GrimAge, but not to Hannum or PhenoAge. Treat a commercial result as approximate and dependent on the chosen clock, and do not base a medical decision on it alone.
Where should I start?
Start with behaviors whose link to health is better documented: regular movement, including muscle-strengthening, and a dietary pattern rich in vegetables, fruit, whole grains and nuts. If you have an underlying condition or pain, talk to your doctor before starting a heavier program.
Conclusion
Exercise and healthy eating have documented links with better health, but the promise of “several years younger” on epigenetic clocks still runs ahead of the evidence. The exercise data are mostly cross-sectional, the nutrition trials are small and heterogeneous, and the twin trial did not report biological age at all. What can be said today is that regular movement, including muscle-strengthening, and a dietary pattern rich in vegetables, fruit, whole grains and nuts are the most reasonable choices, provided we do not draw verdicts from numeric claims or from a commercial test result.
This article does not replace medical advice; if you have an underlying condition or want to begin heavy training, speak with your doctor.
Shan J, Tay JH, Wang W, Tan R, Joshi R, Maier AB, Feng L. Physical activity and biological age measured by DNA methylation clocks: a systematic review and meta-analysis. Lancet Healthy Longev. 2026;7(4):100835. PMID: 42068988 · DOI: 10.1016/j.lanhl.2026.100835
Momma H, Kawakami R, Honda T, Sawada SS. Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases: a systematic review and meta-analysis of cohort studies. Br J Sports Med. 2022;56(13):755-763. PMID: 35228201 · DOI: 10.1136/bjsports-2021-105061
Landry MJ, Ward CP, Cunanan KM, et al. Cardiometabolic Effects of Omnivorous vs Vegan Diets in Identical Twins: A Randomized Clinical Trial. JAMA Netw Open. 2023;6(11):e2344457. PMID: 38032644 · DOI: 10.1001/jamanetworkopen.2023.44457
García-García I, Grisotto G, Heini A, Gibertoni S, Nusslé S, Gonseth Nusslé S, Donica O. Examining nutrition strategies to influence DNA methylation and epigenetic clocks: a systematic review of clinical trials. Front Aging. 2024;5:1417625. PMID: 39077104 · DOI: 10.3389/fragi.2024.1417625
Reynolds LM, Howard TD, Langefeld CD, Vitolins MZ. Epigenetic aging biomarkers in dietary geroscience: feasibility, participant perceptions, and trial design considerations. Geroscience. 2026;48(5):6251-6262. PMID: 42527728 · DOI: 10.1007/s11357-026-02443-0
Freud S. Thoughts for the Times on War and Death (Zeitgemäßes über Krieg und Tod). 1915. [needs further verification: page reference]
Article data are from PubMed (NLM).
Image Credits: Featured image and first image: AI-generated / Gemini 3.1 Flash via OpenRouter.
