The Promise and the Evidence

"Exercise keeps you young" is one of those claims that sounds too convenient to be true. Gyms print it on posters, supplement brands put it on labels, and most of us half-believe it without knowing what it actually means. Younger how — on the inside, in the mirror, or both?

The research gives a more interesting answer than the posters do. Some of the effects are large and well established. Others are real but small. And a few popular ideas — like exercising your face to lift it — rest on very little evidence. There is also a point where training stops protecting the body and starts wearing it down.

This guide goes through what regular exercise does to the markers of ageing inside your cells, to your skin, muscles, and posture, and to the sleep that holds it all together. It also covers how much training is enough and the signs that you're doing too much.

First, What Kind of Exercise Are We Talking About?

"Sport" can mean three quite different things:

  • Exercise for health — walking, running, cycling, swimming, strength training, yoga, group classes. The goal is to feel and function well, not to beat anyone.
  • Amateur competition — local football leagues, park runs, weekend cycling races. Training is more structured and there's a competitive edge, but it's still a hobby.
  • Elite sport — near-daily training from childhood, where the body is a tool for winning. Health and appearance often come second to performance.

When researchers say exercise slows ageing, they almost always mean the first two. The dose they have in mind is set out in the World Health Organization's 2020 guidelines: 150–300 minutes of moderate aerobic activity a week, or 75–150 minutes of vigorous activity, plus muscle-strengthening exercise on at least two days.

How much does that dose matter? In a 30-year study of more than 116,000 American adults, people who met the guidelines for either moderate or vigorous activity had roughly 20% lower risk of dying from any cause over the follow-up period, and similar reductions in deaths from cardiovascular disease and other causes. Doing two to four times the minimum brought a little extra benefit. Beyond that, the curve flattened. There was no clear further gain, but also no sign of harm. Strength training adds its own benefit: a 2022 meta-analysis of 16 cohort studies found that muscle-strengthening activity was linked to lower risk of death, cardiovascular disease, cancer, and diabetes, independent of aerobic exercise — with the largest reduction, about 10–20%, at just 30–60 minutes a week.

That's the foundation: moderate, regular training, well short of elite volume.

Telomeres: The Ageing Marker Everyone Talks About

Inside almost every cell, DNA is packed into chromosomes. At the ends of each chromosome sit telomeres — repetitive stretches of DNA that act a bit like the plastic tips on shoelaces, protecting the genetic material from fraying. Each time a cell divides, its telomeres get a little shorter. When they become too short, the cell stops dividing. Telomere shortening is one of the recognised hallmarks of ageing, and shorter telomeres have been linked to a higher risk of coronary heart disease.

An enzyme called telomerase can rebuild some of that lost length. And exercise seems to switch it on.

The best evidence comes from a 2019 randomised controlled trial in the European Heart Journal. Researchers took 124 healthy but previously inactive people and assigned them to six months of continuous running, high-intensity interval training, resistance training, or no change. Each programme was three 45-minute sessions a week. All three types of exercise improved fitness. But only the two endurance programmes — steady running and intervals — raised telomerase activity two- to threefold and increased telomere length in white blood cells. Resistance training did not.

That doesn't make strength training pointless — it does other important things, as you'll see below. But it suggests that different kinds of exercise work through different biological pathways.

Before you treat telomere length as a scoreboard, three caveats:

  1. The wider evidence is mixed. A 2022 systematic review of 43 studies found that observational studies fairly consistently link moderate-to-vigorous exercise with longer telomeres, but randomised trials show inconsistent results. The optimal type, intensity, and duration are still unknown.
  2. It's usually measured in blood cells, which may not reflect what's happening in your skin, heart, or brain.
  3. Longer isn't automatically better. A large genetic study found that people born with genetically longer telomeres have a higher risk of several cancers. Cancer cells rely on maintaining their telomeres so they can divide indefinitely. The goal is healthy maintenance, not maximum length.

Why a little stress helps

Exercise itself produces reactive oxygen species — the unstable molecules often called free radicals, which can damage cells. That sounds like a problem, but in moderate doses it's the point. Regular training prompts the body to strengthen its own antioxidant defences, so over time it copes better with oxidative stress of all kinds. Researchers describe this as a bell-shaped curve: too little stress and there's no adaptation, too much and damage wins. This is one reason moderate training is protective while chronic overtraining is not.

What Exercise Does to Your Skin

This is where the evidence has become genuinely surprising.

In a 2015 study from McMaster University, researchers found that endurance exercise reduced age-related changes in skin structure in both mice and humans. They traced part of the effect to a signalling molecule, interleukin-15, released by working muscles, which improved how skin cells use energy. In other words, muscles talk to skin, and exercise changes the conversation.

A 2023 trial in Scientific Reports looked at training and skin in people. Sixty-one sedentary, middle-aged Japanese women were assigned to 16 weeks of either aerobic training or resistance training. Both groups improved skin elasticity and the structure of the upper dermis — the layer that holds collagen and elastin, the proteins that keep skin firm and springy. Resistance training also increased dermal thickness. In the resistance group, the researchers linked the changes to lower levels of circulating inflammatory factors. (Several authors work for a cosmetics company, POLA, and it's a single trial, so it needs replicating — but the result is striking.)

One important counterweight: for most people, the biggest external driver of visible skin ageing is ultraviolet light, not a lack of exercise. If you run, cycle, or play sport outdoors, sunscreen and a hat do more for your face than any training programme. It would be a shame to undo the benefits of exercise with years of unprotected sun.

Muscle, Shape, and Posture

The most visible effect of exercise on how you look is muscle.

From middle age, people gradually lose muscle mass and strength. It's a process that, in its advanced form, is called sarcopenia and is a major cause of frailty and disability in later life. A review of meta-analyses on resistance training in ageing adults shows it reliably increases both strength and lean body mass, with more volume and intensity bringing bigger gains. That's true well into older age.

Muscle changes body shape more than weight does. Two people can weigh the same and look quite different depending on how much of that weight is muscle. Strength training is what makes the difference.

Protein supports this, up to a point. A 2018 meta-analysis of 49 trials found that protein supplementation increased gains in muscle size and strength during resistance training. The benefit plateaued at a total intake of about 1.6 g of protein per kilogram of body weight per day. Above that, extra protein added no further muscle mass. For most people who train, somewhere between 1.2 and 1.6 g/kg is a sensible target. That can come from ordinary food — meat, fish, eggs, dairy, legumes — not necessarily supplements. The target counts grams of protein, not grams of food: 100 g of raw chicken breast, for example, contains about 20–23 g of protein.

Posture is often cited as a hidden factor in how old someone looks. A rounded upper back, head pushed forward, and dropped shoulders can make people look older and more tired. Strength training for the back and shoulders, combined with mobility work such as yoga or Pilates, is a reasonable way to build the strength and flexibility that upright posture needs. The research here is thinner than for muscle mass, so treat it as a sensible bonus rather than a proven anti-ageing effect.

Sleep: Where Recovery Actually Happens

Exercise and sleep feed each other. A meta-analysis of 66 studies found that regular exercise has a moderate beneficial effect on sleep quality, small benefits for how long you sleep, and small-to-moderate benefits for how quickly you fall asleep. Sleep, in turn, is when much of the body's repair work happens.

Adults need at least seven hours a night on a regular basis, according to the joint consensus of the American Academy of Sleep Medicine and the Sleep Research Society.

A common piece of advice — never exercise in the evening — turns out to be mostly wrong. A 2019 meta-analysis of 23 studies found that evening exercise does not generally harm sleep and, if anything, slightly increases deep sleep. The exception is vigorous exercise that ends within about an hour of bedtime, which may make it harder to fall asleep and reduce sleep time. A hard session at 7 p.m. is fine for most people. A hard session at 10:30 p.m. before an 11 p.m. bedtime may not be.

Does Face Yoga Work?

Facial exercises — often sold as "face yoga" or "face fitness" — promise to lift sagging cheeks and smooth wrinkles by training the muscles of the face. The evidence is limited to small studies.

The best-known is a 2018 pilot study in JAMA Dermatology. Middle-aged women did 30 minutes of facial exercises daily for eight weeks, then every other day until week 20. Dermatologists rating their photos judged that their faces looked a little younger — about three years younger on average — with fuller upper and lower cheeks. But only 16 women completed the programme, there was no control group, and the exercise regimen was designed by one of the study's co-authors.

That's enough to say face exercises aren't obviously useless. It's not enough to say they work. If you enjoy them, there's little harm. Just don't expect them to replace sunscreen, sleep, or general fitness.

When Training Starts Costing You

The benefits above come from moderate, regular exercise with adequate recovery. Push well past that without enough rest or food, and the balance can tip.

Overtraining. A joint consensus statement from the European College of Sport Science and the American College of Sports Medicine describes a spectrum. Short-term overload followed by rest makes you fitter. Chronic overload without enough recovery can lead to overtraining syndrome: persistent fatigue, falling performance, and mood disturbance that can take months to resolve. There's no single blood test for it. It's diagnosed by the pattern and by ruling out other causes.

Not eating enough for the training you do. The International Olympic Committee calls this Relative Energy Deficiency in Sport (REDs). When energy intake falls short of what training burns, the body cuts back on non-essential functions. The result can include hormonal disruption, loss of menstrual periods, weaker bones, impaired recovery, and mood changes. It affects men as well as women, and recreational athletes, not only professionals.

Performance-enhancing drugs. Anabolic steroids and related drugs are often associated with elite sport, but an Endocrine Society scientific statement points out that the vast majority of users are non-athlete weightlifters. Their use is linked to a higher risk of death and to cardiovascular, psychiatric, hormonal, liver, and kidney problems. The visible effects people notice — acne, hair loss, breast growth in men — are the least of it.

A Plan That Actually Supports Healthy Ageing

  1. Hit the aerobic minimum. 150–300 minutes of moderate activity a week (brisk walking, cycling, swimming, dancing), or 75–150 minutes of vigorous activity (running, fast cycling, intervals), or a mix. Endurance work is the type most clearly linked to telomere maintenance.
  2. Add strength training twice a week. Bodyweight exercises, machines, or free weights, working the major muscle groups. In cohort studies, the benefit peaked at around 30–60 minutes a week.
  3. Include mobility work — yoga, Pilates, or stretching two or three times a week — for joint range and posture.
  4. Recover deliberately. Leave time between hard sessions for the same muscles, and build lighter weeks into your plan. More training needs more recovery, not less.
  5. Sleep seven hours or more, and keep the hardest sessions away from the last hour before bed.
  6. Eat enough, including enough protein — around 1.2–1.6 g/kg a day if you train regularly.
  7. Protect your skin outdoors. Sunscreen and shade protect the gains exercise makes.

Keeping an Eye on the Balance

The line between training that builds you up and training that wears you down is personal. The early signs of tipping over — poor sleep, lingering tiredness, low mood, unplanned weight loss — tend to creep in over weeks, which makes them easy to miss day to day.

This is where a simple record helps. In WatchMyHealth, the Wellbeing check-in logs your sleep hours and how you feel each day, so a slow slide in either is visible as a trend rather than a vague impression. The Weight tracker shows whether your weight is stable or drifting down without you meaning it to — one of the early warning signs of under-eating for your training load. And if you're aiming for a protein target, the Food tracker totals protein alongside the other macronutrients for each day.

None of this needs to be obsessive. A few seconds a day is enough to notice when your routine is working — or when it's time to back off.

The Bottom Line

  • Regular, moderate exercise is one of the most reliable things you can do for healthy ageing: getting the WHO-recommended dose is linked to roughly 20% lower mortality, and strength training adds its own benefit.
  • Endurance training raised telomerase activity and telomere length in a randomised trial; resistance training did not. But telomere length is a rough marker, not a scoreboard.
  • Both aerobic and resistance training improved skin elasticity in a 16-week trial, and resistance training also thickened the dermis. Sunscreen still matters more for your face.
  • Strength training preserves and builds muscle at any age, which shapes how your body looks and works more than your weight does.
  • Face yoga rests on small studies; the best-known had 16 completers and no control group. It's interesting, but not proven.
  • More isn't always better: chronic overtraining, under-eating, and performance-enhancing drugs undo the benefits. Watch your sleep, mood, and weight for early signs.