Does everyone age at the same rate?
People demonstrably age at different rates, and after the age of sixty those differences only grow larger. Inherited traits, lifestyle, sex, and environment together determine the pace.
No, people do not all age at the same rate. Up to the age of sixty, differences in brain volume between people are almost entirely determined by inherited traits. After that, the paths diverge ever more widely: by the age of eighty, up to 50% of the variation in brain size can be explained by the brain shrinking faster in some people than in others.
Whether your brain looks older or younger than your calendar age suggests depends on both inherited tendencies and lifestyle choices and environment. An unhealthy lifestyle widens the gap between actual and predicted brain age, and a larger gap is in turn linked to a higher risk of 69 diseases, including heart, metabolic, and brain conditions. Shorter telomeres, the protective end caps of your DNA, are also linked to faster brain ageing.
Muscle loss does not progress evenly either. Among Asian adults aged 60 and over, an average of just over 16% already have measurable muscle loss, but that figure varies considerably by country and by how it is measured. Skin ageing is the clearest example of how living conditions set the pace: prolonged exposure to ultraviolet light is the main cause of wrinkles, age spots, and loss of elasticity, and this varies enormously from person to person.
Sex also plays a role. Women score higher than men on measures of frailty at every age, yet at the same time have a lower risk of dying. Men have a higher risk of death in every age group, right up to the 90 to 94 age group. Women therefore live longer but are, on average, frailer: ageing manifests differently in the two sexes.
Diet also has an influence on paper: sticking more closely to dietary guidelines is linked to a slightly lower biological age. But in identical twins, who share the same genes and early environment, this link largely disappears. That suggests inherited factors explain much of the association, not diet itself.
This answer draws on several large studies in people, including a study on lung function and cognition with more than 20,000 participants, brain scans followed over time, twin studies, and population research in older Asian adults. The evidence for brain ageing and muscle loss is solid; for diet and epigenetic ageing the evidence is limited, partly because the association largely disappears in twins.
Does stress make you age faster?
Prolonged stress measurably accelerates your biological ageing. Healthy habits can noticeably slow that process.
Does excess weight accelerate ageing?
Excess weight demonstrably accelerates biological ageing, both through shorter telomeres and through epigenetic clocks. The clearest evidence is already visible in young adults, and losing weight appears to be able to partly reverse the process.
Do you age faster if you have chronic pain?
Chronic pain is associated with measurable signs of accelerated biological ageing. Whether the pain is the cause or the other way around has not yet been established.
Does your biological age advance more quickly when you are lonely?
Loneliness is associated with measurably faster biological ageing, and that association has been found across multiple independent measures. Whether loneliness directly causes this has not yet been proven, but the evidence is strong enough to take social connection seriously as part of healthy ageing.
Does your body age faster after a prolonged period of stress?
Prolonged stress is associated with signs of faster cellular ageing, but whether this is truly causal and applies to everyone has not yet been proven. If you want to limit the biological consequences of stress, it pays to pay attention to how you personally experience and process stressful situations.
How does ageing work and how can you slow it down?
Ageing is well described biologically, but there are no proven means of genuinely slowing it in humans yet. For now, focus on what works: sufficient exercise, a protein-rich diet and avoiding overeating.