Aging is inevitable, but how fast your cells age isn’t set in stone. On a molecular level, biological age is measured using something called the epigenetic clock, which isn’t tied to chronological age in calendar years. This clock measures chemical changes, such as DNA methylation patterns, and gauges a person’s “youthfulness” or “agedness” based on their epigenome, the system that controls how our genes are expressed, irrespective of birth-certificate age.

As chronological time marches on, how can you slow your epigenetic clock? Research suggests that lifestyle choices (e.g., diet, exercise, stress management) can slow down epigenetic aging or even rewind it. According to a recent review (Kawamura et al., 2025), working out regularly acts as a powerful geroprotector that slows biological aging by influencing your epigenome. As the authors explain:

Emerging evidence suggests that physical activity, exercise, and physical fitness may delay or reverse epigenetic aging, with implications for the extension of healthspan. […] Interventional studies further suggest that structured exercise training can induce epigenomic rejuvenation, particularly in blood and skeletal muscle.

By engaging in regular physical activity, in other words, you can optimize exercise’s geroprotective power in ways that help “turn back” your body’s epigenetic clock in at least three ways:

1. Geroprotection via Anti-Aging Shields

Exercise’s geroprotective mechanisms don’t rewrite your genetic script. Instead, they provide stage directions that help your genes outmaneuver oxidative stressors while shielding against mitochondrial damage and the wear-and-tear of senescence (growing older).

Moderate-to-vigorous physical activity (MVPA) sustains DNA stability in a “Goldilocks zone” that’s just right for optimizing methylation-related enzymes. Too much methylation can silence protective genes, while too little may activate harmful ones. By nudging methylation toward a youthful balance, MVPA slows the rate at which someone’s epigenetic clock ticks, as measured by indices such as Horvath’s DNAmAge and GrimAge.

Exercise also influences histone modification, another epigenetic mechanism. Histones are proteins that DNA wraps around. When wrapped too tightly, repair genes can’t be accessed. Exercise loosens tightly wrapped packaging, making DNA more resilient to stressors.

Actionable Tip: Aim for at least 150 minutes of moderate-to-vigorous activity per week. Brisk walking, cycling, or swimming all count. Even brief efforts (e.g., taking the stairs) can recalibrate your epigenetic clock.

2. Epigenomic Rejuvenation: Turning Back the Clock

Whereas “physical activity” includes any movement, “fitness” reflects the body’s capacity to adapt to physical exertion. On average, fitter individuals are younger than their chronological age, according to methylation-based epigenetic clocks that predict lifespan and healthspan.

A common measure of being physically fit is cardiorespiratory fitness (CRF), which is based on how efficiently your heart, lungs, and muscles deliver oxygen during aerobic workouts. Higher CRF is strongly linked to epigenomic rejuvenation, meaning DNA methylation patterns shift back to a younger profile and may help “turn back time” on your epigenetic clock.

CRF also supports mitochondrial health. Mitochondria generate energy but also produce reactive oxygen species (ROS) that accelerate aging when unchecked. Exercise strengthens mitochondria, converting what could be harmful oxidants into hormetic signals that protect cells and refresh the epigenome in ways that actively slow aging.

Actionable Tip: Add high-intensity interval training (HIIT) once or twice weekly. Alternating short bursts of effort (like 1 minute of fast running) with recovery (2 minutes jogging) boosts CRF and supports epigenetic rejuvenation.

3. Exercise-Induced Hormesis: Eustress Boosts Resilience

Not all physical activity offers the same level of geroprotection against aging. Light movement, such as a casual stroll or gardening, has clear health benefits, but it often doesn’t create enough cellular stress to spark a strong hormetic response.

Hormesis is the body’s “tough love” mechanism: A challenging (but not overhwhelming) dose of stress activates repair and defense systems, making cells more resilient. Intense exercise, such as resistance training or HIIT, stimulates key pathways like AMPK and sirtuins that regulate DNA repair, mitochondrial growth, and antioxidants.

When it comes to exercise-induced hormesis, the distinction between eustress (“good” stress) and distress (“bad” stress) is key:

Eustress = beneficial stress, like a challenging but doable “sweaty” workout
Distress = harmful overload, such as compulsive overtraining without adequate recovery

Think of hormesis as an inverted U-shaped curve: Too little stress (inactivity) offers minimal benefit, the right amount builds resilience, and too much (overtraining) causes harm. The sweet spot is vigorous activity pursued with enough intensity to trigger repair systems, but not so much that it backfires.

Actionable Tip: Incorporate 75 minutes of vigorous activity per week—roughly three 25-minute sessions of running, climbing the stair master, or uphill hiking. Build up intensity gradually, and listen for warning signs associated with injury-causing overload.

Take-Home Message

The key to unlocking exercise’s anti-aging benefits lies in pushing your body enough to trigger hormetic adaptations without crossing the line into distress. Whether you’re walking briskly, running, cycling, or doing HIIT, finding the right “dose” of duration, intensity, and frequency for your fitness level is essential.

By understanding the inverted U-shaped curve of hormesis and fine-tuning exertion within the sweet spot between burnout and relaxation, you can create personalized workouts that slow aging and safeguard your DNA. Harnessing exercise’s geroprotective power can help keep your body biologically younger for years to come.