Your lifestyle says more about your biological age than your date of birth

This article is written by Dr. Arne Løberg Sæter, physician and Chief Medical Officer at Amino.

As a doctor, I am occasionally struck by how big a difference there can be between the age listed in the medical record and the age the patient in front of me actually appears to be.

My experience as a doctor

Recently, I went out to the waiting room to fetch my next patient, a man in his 50s. There sat no one who fit the description. Only an older man I assumed was around 70. I went back into my office to check, but the screen showed that the patient who had arrived was indeed the 50-year-old I was supposed to fetch. Excess weight, diabetes, smoking, and physical inactivity had left their mark. His face, posture, gait – everything told a different story than his date of birth.

A few days earlier, I had had the exact opposite experience. A brisk and upright woman I assumed was in her seventies came in with sprightly steps, obvious zest for life, and clear speech. She was over 90 years old, and still an active runner.

It is such contrasts that many attempt to describe with the term biological age.

We still have no perfect blueprint for how biological age should be measured. Many try to create tests and biological clocks, but none of them provide the whole answer. Nevertheless, research points in the same direction: several measures of biological aging seem to indicate more about the risk of disease and death than chronological age alone.

Intuitively, this makes sense. Two people can be the same age on paper, but have completely different physical capacities, metabolic health, blood pressure, inflammation, muscle mass, and function. The difference between biological and chronological age can therefore be significant – and it says something important about what aging is actually about.

Such contrasts are not exceptions. Every time, I am struck by the same thought: physical inactivity seems to be a bigger factor in aging than the clock.

If we had a medicine as effective and free of side effects as physical activity, almost everyone would take it – regardless of the price. The difference is that this "medicine" is often free.

Large studies, such as the Global Burden of Disease, suggest that a large proportion of the disease burden in society can be prevented, and physical activity is probably one of the most important single factors we can influence ourselves.

Inactivity comes first, aging follows

The classic narrative is that we move less because we get older. But there is much to suggest that the causal relationship also goes the other way: We age faster because we move less.

Studies of older people who have remained physically active throughout their lives show a completely different picture than what many associate with aging. Fit 70-year-olds can have the same cardiorespiratory fitness, mitochondrial function, and muscle quality as inactive people decades younger. Booth and colleagues summarized this in Comprehensive Physiology in 2012: physical inactivity is a major cause of more than 30 chronic conditions, and much of what we call age-related changes in the muscle, heart, and brain may be due to a loss of movement stimulus – not just the passage of time.

Perhaps the clearest example comes from the classic Dallas Bed Rest Study. It showed that three weeks of bed rest in healthy 20-year-olds caused a greater decline in fitness than what the same participants experienced through 30 years of normal aging. The study was later followed up and published by McGuire and colleagues in Circulation in 2001.

This is quite a dramatic finding. If three weeks in bed can mimic several decades of aging in the body, what then do decades of low everyday activity do?

Modern studies point in the same direction. Krogh-Madsen and colleagues showed in the Journal of Applied Physiology in 2010 that just two weeks with significantly fewer daily steps led to measurable insulin resistance, more visceral fat, and poorer vascular function in healthy young adults.

At the cellular level, we see the same thing. Mitochondrial function, insulin sensitivity, muscle mass, blood vessels, and the brain are negatively affected by inactivity and positively affected by exercise. Werner and colleagues showed in Circulation in 2009 that endurance-trained middle-aged individuals had longer telomeres than their inactive peers. Erickson and colleagues showed in PNAS in 2011 that moderate aerobic exercise could increase the volume of the hippocampus in older adults – an area in the brain crucial for memory, learning, and spatial orientation.

This does not mean that exercise makes us immortal. But it shows that the body is far more plastic than many believe. It doesn't just decay because time passes. It adapts to the life we actually live.

If activity were a pill

If we had a medicine that worked as broadly as physical activity, the vast majority would probably want it. It would impact the risk of cardiovascular disease, type 2 diabetes, depression, certain types of cancer, dementia, falls, muscle loss, and premature death. Quite simply, a great many of the signs of aging.

The difference is that this "medicine" is largely free.

Wen and colleagues showed in The Lancet in 2011 that just 15 minutes of moderate daily activity was linked to lower mortality and more years of life. Arem and colleagues showed in JAMA Internal Medicine in 2015 that 150–300 minutes of moderate activity per week was associated with an approximately 31% lower risk of premature death, and that more activity provided further benefits.

Step data points in the same direction. Saint-Maurice and colleagues showed in JAMA in 2020 that taking more daily steps was clearly associated with lower mortality, with benefits increasing up to around 12,000 steps daily. Mandsager and colleagues showed in JAMA Network Open in 2018 that high cardiorespiratory fitness was associated with far lower mortality than low fitness.

This does not mean that fit people do not get sick or die. But they die later on average – and often live a larger part of their lives with good physical function and less illness.

When looking at specific diseases, the picture is also clear. Pedersen and Saltin summarized in the Scandinavian Journal of Medicine & Science in Sports in 2015 that physical activity is an evidence-based treatment for at least 26 chronic diseases, ranging from type 2 diabetes and cardiovascular disease to anxiety, depression, COPD, and several cancers.

The latest report from the Lancet Commission on Dementia from 2024 considers physical inactivity as one of several modifiable risk factors for dementia. This is particularly important because dementia remains a disease for which we have limited treatment options. Once the disease has developed, it is difficult to reverse the trend. Therefore, prevention becomes all the more critical.

Even though most people know that physical activity is healthy, I believe many underestimate how great the effect actually is. We often overestimate the importance of age, and underestimate the importance of lifestyle.

Given that physical activity has such a well-documented effect on so many age-related diseases, function, and lifespan, it perhaps should have been given a far larger place in both medicine and society. More people would likely be more active if the effect had come in pill form.

But better information is only part of the solution.

It's not just about pulling yourself together

At the same time, it is important to be honest: "Pulling yourself together" helps. If a person exercises more, walks more, eats less, and keeps at it long enough, it will usually lead to better health, lower weight, and a lower risk of lifestyle diseases.

But that does not explain why so many fail to do so.

The big question is not whether willpower works. It does. The question is why modern humans need so much willpower to live in a way the body can tolerate.

In practice, we have the same genes as people had a few hundred years ago. Yet, very few struggled with obesity, diabetes, and other lifestyle-related diseases to the same degree as we do today. That does not mean people in the past were morally stronger. They just lived in a different environment.

In the past, movement was to a greater extent built into everyday life. Food required more work. Transportation required more physical activity. Work was more often manual. And access to cheap, energy-dense, and easily consumable food was far lower.

Today, it is the opposite. We can work, shop, communicate, entertain ourselves, and move around almost without using our bodies. At the same time, the food around us is more accessible, more energy-dense, and often designed to make us eat more than we need. It is convenient. But it comes with a price.

Our bodies are still built for movement. Our everyday lives are increasingly designed for a sedentary lifestyle.

"Pull yourself together" is not wrong. It helps to exercise more, walk more, and eat less if you manage to do it consistently over time. But for many of us, it is difficult to achieve in an environment that constantly pulls in the opposite direction. When everyday life makes sitting still easy, movement unnecessary, and energy-dense food constantly available, lifestyle changes become more than just a question of knowledge or willpower.

We must build a society for movement

If physical activity is to become public health, society must be built for movement.

We need cities and towns where walking and cycling are the easy choice, not the brave one. Workplaces that facilitate less sitting still. Schools that prioritize physical activity, not just theory and screens. And healthcare services that, to a greater extent, use exercise as a treatment, not just as a piece of general lifestyle advice at the end of a consultation.

Those who often have the most to gain from physical activity are also those who may find it hardest to get started alone: patients with chronic illnesses, those on sick leave, the disabled, the elderly, people with pain, excess weight, low self-efficacy, or little energy.

For many of these individuals, a brochure is not enough. They need low-threshold offers, guidance, structure, and follow-up.

When exercise demonstrably works as medicine, we must also dare to organize it more like medicine. And we must remember to build good habits early.

Children's joy of movement is a capital we are wasting

This starts early. Norwegian children and adolescents move less than before, and many adolescents do not meet the recommendation of at least 60 minutes of daily physical activity.

This is serious. Not because all children should become athletes, but because bodily mastery during childhood and adolescence lays the foundation for lifelong activity. Inactive children more often become inactive adults. And when organized sports become more expensive, physical education is deprioritized, and screen time displaces free play, we lose something that is difficult to get back.

Prevention does not start when blood pressure, blood sugar, and weight have already begun to rise. It starts with how we structure the everyday lives of our children.

From treating illness to a society in movement

The WHO estimated in its Global Status Report on Physical Activity from 2022 that physical inactivity will contribute to nearly 500 million new cases of non-communicable diseases globally between 2020 and 2030. Inactivity is also linked to millions of premature deaths every year.

Therefore, the question shouldn't be whether we can afford to invest in movement. My claim is that we cannot afford not to.

We cannot abolish aging. But much of what we call aging is also something else: the consequence of a body built for movement living a life without movement.

The 50-year-old in the waiting room was not just old before his time. He was inactive before his time.

The 90-year-old runner was not a miracle. She was a reminder of what the body can still endure, preserve, and develop when it is put to use.

We have one of the most effective "medicines" that exists, available for free and without serious side effects. What we lack is not evidence. What we lack is a society that takes the evidence seriously – and makes movement a natural part of everyday life for everyone.

(For info: Details regarding the patients, such as age, gender, and time, have been altered for de-identification).

Dr. Arne Løberg Sæter / Chief Medical Officer at Amino