101 Facts About Ageing #52: Ageing And Weight Gain

As Daniel Patrick Moynihan, an American sociologist, politician, and diplomat once said: “Everyone is entitled to his own opinion, but not his own facts”. And we wholeheartedly agree. A shared set of facts is the first step to building a better world with longevity for all. In that spirit, we are creating a series that covers 101 indisputable facts about ageing, health and longevity.

On average, body weight tends to increase with age until late life, at which point it may decrease. The increase in body weight is usually the result of increased adipose (fat) tissue, which contributes to increased risk of age related diseases such as type II diabetes and heart disease. The graph below shows the proportion of different age groups that fall into each category of body mass index (BMI) in Sweden as of 2020. BMI is calculated by dividing one’s body weight (kilograms) by the square of one’s height (metres). Being overweight or obese is most common among those aged 50-64. Slightly fewer 65+ year-olds are overweight or obese, but over 65s are still more likely to be overweight/obese than those below the age of 50.

We still don’t know for certain why people gain weight as they age, but it’s likely to be a combination of different factors that may vary from person to person. Weight gain requires a calorie surplus (more calories consumed than calories burnt), which may become more likely with age for various reasons:

• People tend to exercise less as they age due to life commitments or due to age related disease/disability in old age.
• Muscle mass may decline due to lack of exercise and due to the effects of the ageing process itself. Muscle tissue is a major consumer of energy, even when it is inactive, and so loss of muscle mass reduces the basal metabolic rate (your calorie expenditure at rest).
• People tend to eat more as they age. Increased fat tissue, hormonal and neurological changes may affect appetite control and encourage overeating.

One recent study suggested that energy expenditure doesn’t actually change very much between the ages of 20 and 60, implying that overeating might be the primary culprit for weight gain between these ages.