Why Does Your Body Shape Change as You Get Older?

Have you ever noticed that your body doesn't look quite the same as it did ten or twenty years ago, even though your weight hasn't changed very much? Perhaps your waistline has become a little larger, your arms or legs look different, or clothes that once fitted comfortably now feel tighter in certain places. It's something many people experience as they get older, and while it's easy to assume that it's simply part of ageing, there are several reasons why our body shape can change and one of the biggest factors is muscle mass.

From around our thirties, we can gradually begin to lose muscle if we're not doing enough to maintain it. This process is known as sarcopenia, although the rate of muscle loss varies considerably between individuals. Muscle gives our bodies much of their shape and structure and when we lose muscle, particularly around our legs, arms and shoulders, our appearance can change even if the number on the scales stays the same. It's also possible to lose muscle while gaining body fat, meaning your overall weight changes very little despite a noticeable difference in body composition. The encouraging thing is that muscle loss isn't something we simply have to accept. Research consistently shows that resistance training can help preserve and build muscle throughout adulthood, including in people well into their seventies and eighties.

Where we store body fat can change too. As we get older, some people notice that more fat accumulates around their abdomen rather than their hips, thighs or other areas. Hormones do play a role in this, although they're not the only factor. For women, the hormonal changes associated with menopause can influence where fat is stored, with a greater tendency towards abdominal fat. This can happen even without a significant increase in overall body weight. For men, changes in testosterone levels, body composition and lifestyle can also contribute to changes in fat distribution, although these changes vary from person to person.

Genetics, sleep, activity levels and overall health all influence how our bodies respond as we age. It's important to recognise that these changes aren't simply a reflection of someone's effort or discipline, our bodies are influenced by a complicated combination of biological and environmental factors. We often get asked about metabolism and whether that slows down with age? It's a common explanation for weight gain, but the science is a little more interesting than that - a study published in 2021 examined energy expenditure across the lifespan and found that, after accounting for differences in body size and composition, average daily energy expenditure remained relatively stable between approximately 20 and 60 years of age.

That doesn't mean our energy requirements never change during those years. If we lose muscle, become less active or spend more time sitting down, the amount of energy we use each day may decrease. But this is different from suggesting that our metabolism suddenly slows dramatically when we reach forty. After around sixty, research suggests that energy expenditure does begin to decline more noticeably, even after accounting for body composition. So while metabolism is part of the picture, it doesn't explain every change we see in our bodies, our everyday habits can make a difference as well. Think about how your lifestyle might have changed over the past twenty years. Perhaps you used to walk more, had a more physically demanding job or spent less time sitting down. Family responsibilities, work commitments, injuries and changes in routine can all affect how active we are. These differences can accumulate gradually, often without us noticing.

Sleep also matters - poor sleep can influence appetite, food choices and energy levels, making it more difficult to maintain the habits that support our health. And while nutrition plays an important role in body composition, it's worth remembering that our nutritional needs and circumstances can change throughout adulthood too. So, can we do anything about it? Absolutely, strength training is one of the most useful things we can do to maintain muscle mass as we age. It doesn't need to involve lifting enormous weights, but it does need to provide enough challenge for our muscles to adapt. Staying generally active throughout the day, eating enough protein as part of a balanced diet and getting adequate sleep can also support healthy body composition. And perhaps most importantly, consistency matters far more than trying to make dramatic changes overnight.

It's also worth remembering that body weight and body shape don't tell us everything about our health. Two people can weigh exactly the same but have very different amounts of muscle and body fat. Equally, someone can improve their strength, fitness and physical health without seeing a dramatic change on the scales. Ageing brings changes to our bodies, but it doesn't mean we're powerless to influence how we feel, move or function. Rather than focusing entirely on getting back to the body you had at twenty-five, perhaps a more useful goal is building a body that stays strong, capable and healthy for the years ahead.