Even if you feel invincible in your 30s, the ageing process is already subtly at work. By the time you reach your 70s, most people notice more stiffness, reduced strength, and perhaps a slight decline in cognitive sharpness. Sleep patterns often shift, leaving you drowsier in the evenings and waking earlier, and population averages suggest many will face at least one chronic health condition.

Yet researchers increasingly argue that these outcomes are not inevitable. "Based on what we now know, most people could expect to live to 90 or even 95 in good health if they were to optimise their lifestyle," says Eric Verdin, president and chief executive of the Buck Institute for Research on Ageing in California. "And that's very far from where we are, where most people live to 65 or 70 in good health, and then become ill and suffer all the indignities of old age."

Verdin emphasizes that improving your health is possible at any age through positive lifestyle changes, whether that’s exercising more, eating better, or reducing alcohol, but the earlier you start, the greater the benefits. In particular, your 30s represent a pivotal decade. It’s when many physiological systems, muscle mass, bone density, metabolic regulation, begin showing the first subtle age-related changes. "It does highlight this period as an important opportunity to reinforce behaviours that build long-term resilience," says João Passos, a professor of physiology.

To understand the potential of healthy ageing, scientists often study those who defy typical age trends, such as masters athletes. These are individuals over 35 who continue competing in sports like running or cycling well into their 60s and beyond. Paul Morgan, a senior lecturer in nutrition and metabolism at Manchester Metropolitan University, notes that these athletes often experience a slower decline in cardiovascular function and muscle strength, maintaining mobility and independence longer than average. "They have this additional reserve which acts as a protective barrier through the middle stages of life," he explains.

Morgan suggests that everyone can benefit from aiming to reach the highest physical peaks possible in their 30s, particularly in aerobic capacity, flexibility, and muscle strength. Lower-body muscles are especially important. "I always see the muscle groups in the lower limbs that are responsible for locomotion as having the biggest role to play in maintaining independence, and with that, good health in later life," he says.

Playing sports is one practical way to achieve this. Research consistently links racquet sports, such as tennis or badminton, with longer lifespans. A 2025 Japanese study also highlighted cycling, showing that older adults who cycle regularly are less likely to require long-term care or die prematurely. Running over 75 minutes per week can slow certain ageing processes, though extreme endurance efforts, such as marathons, may accelerate some aspects of biological ageing.

Even modest activity helps. "Even a brisk 15-minute walk after a meal can make a meaningful difference," says Aditi Gurkar, an assistant professor of medicine at the University of Pittsburgh. Just five minutes of moderate to vigorous activity daily may slow brain ageing.

Protecting Your Brain

Your 30s are also crucial for building cognitive resilience. Simple habits like regular dental care, good brushing, avoiding smoking, and limiting sugar can help protect the brain. Research links periodontal disease, a gum condition with elevated inflammation, to an increased risk of cognitive decline, likely due to the chronic systemic inflammation it triggers.

Reducing alcohol intake is another key step. Alcohol affects gene expression in ways that accelerate ageing and disrupts sleep. Verdin highlights consistent sleep patterns as essential for preventing age-related brain shrinkage and lowering dementia risk. "Even if you're lacking sleep for one night, your metabolism changes, and your willpower to do all the things that are keeping you healthy goes away," he says.

Verdin personally sets an alarm each night, not to wake up, but to remind himself to go to bed. "The reason for this is we're circadian beings," he explains. "Our whole biology, from gene expression to metabolism, is in synchrony with the 24-hour cycle, and so I tell people, going to bed at the same time each day helps your body to stay really well synchronised to all of this."

Nutrition and Fasting

Nutrition in your 30s can also shape how you age. Verdin recommends giving the body extended periods without eating, for example through intermittent fasting. While many promote a 16:8 schedule, 16 hours of fasting and eight hours of eating, even a 12:12 split offers significant benefits. "Essentially when you're fasting, that allows your body to focus not on digesting but on repairing," he says. "I tell people, when you are eating, you are building. When you're fasting, you are repairing."

Consuming more fruit and vegetables at the expense of ultra-processed foods could also make a difference. Gurkar points to work that she and others have carried out show that people who ingest higher amounts of dietary carotenoids, plant chemicals found in vegetables such as sweet potatoes and carrots, and fruits like mango and apricots, age more slowly, possibly because these chemicals can play a role in protecting our cells from a form of damage called oxidative stress. Overall, Passos is convinced that the choices we make in early adulthood can have a lasting impact on how we age. He points to large studies which have tracked tens of thousands of people in the US for decades, such as the Framingham Heart Study and the Nurses' Health Study, which reveal that people who maintain healthier lifestyles in midlife have lower risks of cardiovascular disease, cognitive decline and frailty, even decades later.

"By maintaining healthier behaviours in our 30s, we may prevent or delay subtle molecular and cellular changes that, if left unchecked, accumulate over time and contribute to functional decline in our 70s," says Passos. "While I don't believe that by doing this we can stop ageing, we can certainly shape its trajectory."

Ultimately, the choices you make in your 30s, limiting alcohol, choosing a sport you can enjoy long-term, maintaining sleep regularity, eating more plant-based foods, and giving your body breaks from constant eating, can pay dividends decades later. Your heart, muscles, joints, and brain will all benefit as you age, helping you stay stronger, sharper, and more independent well into your 70s and beyond.