1 / Why Your Body Changes After 45 and Why Strength Matters More Than Ever

There is a point in midlife when many women begin to feel that their body has changed the rules.

The same weight may sit differently. Muscle seems harder to maintain. Getting up from the floor requires slightly more effort than it once did. Recovery after exercise takes longer, and things you never thought about before, such as bone density, balance or whether you can comfortably carry something heavy, suddenly begin to matter.

It is easy to put all of this down to menopause. But that is only part of the story.

Ageing and menopause overlap, but they are not the same process. Changes in muscle, cardiovascular fitness and physical capacity begin gradually during adulthood, while the hormonal changes around menopause can accelerate some processes, particularly bone loss and changes in body composition.

Understanding what is happening matters because much of the physical decline we associate with ageing is not completely inevitable. We cannot stop biological ageing, but we can have a remarkable influence on how much strength, muscle, bone and physical capacity we carry with us into later life.

Body changes after 45: healthy ageing is really about maintaining capacity

When we talk about body changes after 45 and healthy ageing, the conversation often drifts towards wrinkles, supplements, longevity hacks and how to remain “young.” I think there is a much more useful definition.

Healthy ageing is about maintaining enough physical and metabolic capacity to continue doing the things you want to do.

Can you walk for an hour when you travel? Carry your suitcase? Lift something onto a shelf? Get up from the floor? Climb stairs? Recover from an illness without losing your independence? Catch yourself if you stumble?

At 50, these questions may seem almost ridiculously easy. At 80, they can determine whether you continue living independently.

The important part is that the physical reserve you will need later is being built and maintained now.

Muscle loss doesn't suddenly start at menopause

We gradually lose muscle mass and strength as we age, particularly when we are physically inactive. The process eventually contributing to clinically significant loss of muscle mass, strength and function is known as sarcopenia.

But muscle mass is only part of the story. Strength can decline faster than muscle size, because ageing also affects the nervous system, muscle quality and how effectively the brain and muscles communicate.

This means that simply looking at your arms or standing on a scale tells you very little about how well your muscular system is ageing.

Menopause may contribute to changes in body composition and muscle function, but it is too simplistic to say estrogen disappears and therefore muscle disappears. Age, activity, protein intake, illness, insulin resistance, sleep and the type of physical stimulus you give your muscles all matter.

The biggest practical distinction is between a muscle that is regularly challenged and one that isn't.

Muscle needs a reason to stay

Your body is extremely economical. Maintaining metabolically active tissue costs energy, and muscle that is rarely required to produce significant force provides little reason for the body to preserve its full capacity.

This is where resistance training becomes so important.

When muscle is challenged against sufficient resistance, the mechanical and metabolic signals generated by that work stimulate adaptation. Muscle protein turnover changes, neuromuscular coordination improves and, with adequate training and nutrition, strength and muscle can be maintained or increased even later in life.

This is why ordinary movement and strength training are not interchangeable.

Walking is excellent for health, and I want women walking. But walking generally does not challenge the muscles of the entire body sufficiently to replace progressive resistance training.

Your heart needs movement. Your muscles need load.

Your muscles become less responsive to weak signals

Another important change with ageing is sometimes described as anabolic resistance.

Muscle is constantly breaking down and rebuilding proteins. Eating protein and performing resistance exercise stimulate muscle protein synthesis, helping maintain and repair muscle tissue.

With increasing age, muscle can become less responsive to relatively small anabolic signals. In practical terms, the stimulus that was enough when you were younger may no longer produce the same response.

That does not mean the ageing body cannot build muscle. Quite the opposite. Older adults can improve strength and muscle substantially with appropriate resistance training.

It means the signal needs to be meaningful.

A tiny amount of protein, combined with very little muscular loading and hours of sitting, is not an ideal recipe for maintaining muscle into your seventies and eighties. Adequate nutrition and sufficiently challenging resistance training become more important, not less.

Muscle is much more than something that makes you strong

This is where muscle becomes particularly interesting from a functional medicine perspective.

Skeletal muscle is one of the largest tissues in the body and an important site for glucose disposal. After you eat carbohydrates and blood glucose rises, insulin helps glucose enter tissues, and skeletal muscle is a major destination for that glucose. Maintaining active muscle therefore contributes to insulin sensitivity and metabolic health.

Muscle is also an endocrine organ. Contracting skeletal muscle releases signalling molecules, often referred to collectively as myokines, which communicate with other tissues and are involved in metabolic, inflammatory and adaptive processes.

And muscle acts as a reserve of amino acids. During serious illness, injury or prolonged inactivity, the body may break down muscle protein to provide amino acids needed elsewhere.

This helps explain why entering older age with very little muscle can leave someone more vulnerable when illness or hospitalisation occurs.

Muscle isn't cosmetic padding around your skeleton. It is metabolically and functionally active tissue that contributes to your resilience.

Menopause has an especially important effect on bone

Bone is not a static structure. It is living tissue that is constantly being broken down and rebuilt through a process called bone remodelling.

Estrogen plays an important role in regulating that process. As estrogen declines around menopause, bone resorption can begin to exceed bone formation, leading to accelerated bone loss. The years around the final menstrual period can therefore represent a particularly important period for skeletal health.

This is one area where menopause itself has a very clear physiological impact.

If enough bone is lost, osteoporosis can develop, increasing the risk of fragility fractures. These are fractures occurring with relatively minor trauma, often involving the hip, spine or wrist.

And this is not simply a problem of “weak bones.” A hip fracture in later life can have profound consequences for mobility, independence and overall health.

This is why I would much rather we start thinking about bone at 45 or 50 than discover at 70 that we should have been thinking about it twenty years earlier.

Bone also needs a reason to stay strong

Like muscle, bone responds to mechanical loading.

Weight-bearing activity and resistance exercise expose bone to forces that help stimulate bone adaptation. The type, direction and magnitude of those forces matter, which is why simply taking calcium while remaining physically inactive is not a complete bone-health strategy.

Nutrition still matters enormously. Bone requires adequate protein and minerals including calcium, while vitamin D is important for calcium absorption and normal bone physiology. But bone health is the result of the interaction between nutrition, hormones, mechanical loading, genetics, medications and other health factors.

This is another reason muscle and bone should not be discussed separately.

Strong muscles generate forces through bone. They also improve physical function and help protect against falls. You want strong bones, but you also want the muscular system capable of keeping those bones off the floor.

Body composition begins to matter more than body weight

Many women notice that their waist changes around menopause even when the number on the scale has not changed dramatically.

Menopause is associated with changes in body-fat distribution, including a tendency towards greater central or visceral fat accumulation. Ageing can simultaneously contribute to loss of lean tissue, particularly when activity and resistance training are inadequate.

This creates a situation where body weight alone can become increasingly misleading.

A woman may weigh almost exactly what she weighed ten years ago while having less muscle and more abdominal fat.

This matters metabolically because visceral fat is not simply passive energy storage. Excess visceral adiposity is associated with insulin resistance, inflammation and increased cardiometabolic risk.

So when we talk about healthy ageing, I am much less interested in whether you can return to the weight you were at 35 than in what your body is made of and what it can do.

Strength and metabolism are closely connected

As muscle declines and activity decreases, glucose disposal can become less efficient. At the same time, visceral fat may increase and insulin sensitivity can deteriorate.

This is one reason metabolic health and strength should never live in separate health categories.

Resistance training can improve insulin sensitivity and glucose regulation even without dramatic weight loss. Aerobic exercise improves cardiovascular fitness and metabolic health. Combining both gives us something far more valuable than exercise performed purely to burn calories.

The goal is not simply to make the body smaller.

It is to make it more metabolically capable.

Cardiovascular fitness is another form of physical reserve

Strength receives a lot of attention in healthy ageing, and rightly so, but your cardiovascular system needs training too.

Cardiorespiratory fitness describes how effectively the circulatory and respiratory systems deliver oxygen to working muscles and how effectively those muscles use it. One commonly used measure is VO2 max, or maximal oxygen uptake.

Cardiorespiratory fitness tends to decline with age, particularly in people who become less active. Higher fitness levels are strongly associated with lower cardiovascular and all-cause mortality risk.

But VO2 max is not merely an athlete's number.

It translates into everyday capacity. Can your cardiovascular system comfortably support walking uphill, climbing stairs, carrying shopping or keeping up with other people when travelling?

The more physical reserve you have, the further ordinary life remains below your maximum capacity.

That is an extremely useful way to think about fitness as we age.

Power disappears faster than most women realise

Strength is the ability to generate force. Power is the ability to generate force quickly.

You need strength to stand up from a chair. You need power to do it quickly. You need strength in your legs to walk. You need power when you trip and have a fraction of a second to stop yourself from falling.

Muscular power tends to decline particularly rapidly with ageing, which can eventually affect mobility and independence.

This is one reason healthy-ageing exercise should not eventually consist only of slow, gentle movement. Appropriate training can help preserve the ability to produce force efficiently and, where safe and suitable, quickly.

We will look at this much more practically later in the series. For now, I simply want you to understand that being able to move is not the same thing as being physically capable.

Balance is not something to worry about when you are 80

Balance depends on several systems working together, including vision, the vestibular system of the inner ear, sensation from muscles and joints, nervous-system processing and muscular strength.

Like other physical abilities, balance can deteriorate when it is not challenged.

This matters because falls become increasingly consequential as we age, particularly when osteoporosis is present. Preventing fractures therefore requires more than improving bone density. We also want to reduce the likelihood of falling in the first place.

Balance can be trained. Strength can be trained. Reaction can be trained.

Waiting until somebody has already begun falling is a very late time to decide that these abilities matter.

Sitting quietly accelerates the problem

You can technically “exercise” and still spend most of your life sedentary.

An hour at the gym does not completely erase ten hours spent sitting. Ordinary daily movement matters independently of formal exercise.

Walking to the shops, taking stairs, gardening, carrying things, standing, moving around the house and breaking up long periods of sitting all contribute to total physical activity.

This everyday movement is sometimes called non-exercise activity thermogenesis, or NEAT, when discussed in the context of energy expenditure. But I don't particularly want you thinking about it as another way to burn calories.

I want you to think about it as repeatedly reminding the body: we still use this system.

Recovery changes too

One mistake women sometimes make when they become concerned about ageing is going from very little exercise to trying to train intensely every day.

More is not automatically better.

Exercise creates a stimulus. Adaptation occurs when the body has sufficient nutrition and recovery to respond to that stimulus. Sleep, adequate energy intake, protein and sensible spacing of demanding training sessions all contribute to that process.

Recovery capacity may change with age, and menopause symptoms such as severe sleep disruption can make recovery considerably harder.

This does not mean women after menopause are fragile and should exercise gently forever. It means training should be progressive enough to create adaptation and intelligent enough to allow recovery.

Those are very different things.

Frailty is not simply being thin or old

Frailty is a clinical concept describing reduced physiological reserve and increased vulnerability to stressors.

A frail person may cope reasonably well under normal circumstances but deteriorate dramatically after an infection, fall, operation or hospital admission because there is little reserve available.

Loss of muscle, low strength, reduced activity, poor nutrition and chronic disease can all contribute to this vulnerability.

This is why I dislike the idea that strength training is an optional fitness hobby.

We are not training simply to have toned arms. We are building reserve.

The reserve to recover from pneumonia. The reserve to rehabilitate after surgery. The reserve to get yourself off the floor. The reserve to continue carrying your own groceries and living in your own home.

That is a very different reason to exercise.

Your future independence is being built earlier than you think

At 50 or 60, it is easy to assume that physical decline is a problem for much later.

But we do not suddenly become frail at 80.

We arrive there carrying the consequences of decades of muscle, bone, cardiovascular health, nutrition, disease, physical activity and inactivity. Genetics and unavoidable illness matter, of course, but so does the physical reserve we have accumulated before something goes wrong.

This changes the purpose of exercise completely.

Instead of asking, “How many calories did I burn?” ask whether today's activity gave your muscles, bones, heart and nervous system a reason to remain capable.

Instead of exercising because you dislike your body, train because you intend to keep using it.

What I want you to take away from this

Healthy ageing is not about desperately trying to stop ageing. It is about preserving the systems that allow you to remain capable as ageing happens.

Muscle, bone, cardiovascular fitness, metabolic health, balance and physical function are interconnected, and all of them respond to how you live and train.

After 45, strength becomes increasingly valuable not because you need to look athletic, but because strength creates options. It allows you to lift, carry, climb, travel, recover, protect yourself from falls and remain independent. The earlier we build that reserve, the more of it we have available later.

In the next article, we will turn this physiology into a practical starting point and work out what to do first, whether you currently exercise regularly or haven't lifted anything heavier than a shopping bag in years.

Next: Where to Start If You Want to Be Stronger and Healthier After 45

You can explore more articles, free and paid resources, my book and programmes in the Healthy Ageing & Strengthsection of Feel Good Menopause.