Why you are losing muscle
after 35 and what to do about it.

What is sarcopenia and why does it start at 35?

Sarcopenia is the gradual loss of skeletal muscle mass that begins in your mid-thirties and accelerates as you age. The name comes from the Greek for flesh and poverty, which is about as blunt as medical terminology gets. From roughly age 35, most adults lose between 1 and 2 percent of their muscle mass per year. By the time you reach 60, that can amount to a significant reduction in the total muscle your body carries.

This is not something that happens because you stopped trying or because you made bad choices. It is a normal physiological process driven by changes in hormone levels, reduced protein synthesis efficiency, and the nervous system becoming less effective at recruiting muscle fibres. Your body starts doing less with the same inputs.

What makes sarcopenia worth understanding is not the process itself. It is the downstream effects. Muscle is not just something that makes you look stronger. It is a metabolically active tissue that influences almost everything about how your body functions day to day.

What muscle loss actually does to your body

Your metabolism slows down

Muscle tissue burns calories at rest. Fat tissue does not. When you lose muscle mass, your resting metabolic rate drops. This is why people in their forties and fifties often find they are eating the same as they always have but gaining weight anyway. It is not a discipline problem. It is a body composition problem. Less muscle means fewer calories burned at rest, and the same diet that maintained your weight at 28 now creates a surplus at 42.

Your joints start to suffer

Muscles are the primary shock absorbers and stabilisers for your joints. Your knee, for example, is protected by the strength of the quadriceps and hamstrings around it. When those muscles weaken, the joint itself absorbs more load with every step, every staircase, every time you stand up from a chair. The aching knees, the sore hips, the chronic lower back pain that many adults over 35 accept as normal are very often symptoms of muscle weakness, not joint degeneration.

Your energy drops

This one is less obvious but worth understanding. Muscle tissue plays a significant role in glucose regulation. When you have good muscle mass, your body is efficient at using blood sugar for energy. As muscle mass declines, this efficiency reduces. Blood sugar becomes less stable, insulin sensitivity decreases, and the result is the kind of deep, bone-level fatigue that arrives in the afternoon and does not respond well to caffeine.

Your bone density decreases

Muscle and bone are closely linked. The mechanical stress that comes from muscles pulling on bones during resistance training is one of the primary signals that tells your body to maintain bone density. Less muscle activity means less of that signal. For women heading into perimenopause, where oestrogen-driven bone protection is already declining, this becomes particularly significant. Osteoporosis risk increases substantially in the decade after menopause, and strength training is one of the most effective ways to reduce it.

Why cardio alone does not solve this

Running, cycling, swimming, walking. All of them are good for cardiovascular health and there is real value in doing them. But none of them address sarcopenia. Cardio does not build muscle. In fact, excessive cardio without adequate nutrition and strength work can actually accelerate muscle loss in older adults, as the body breaks down muscle tissue for fuel.

If your main form of exercise is cardio, you are working on one dimension of health while another dimension quietly deteriorates. This is why so many people who walk regularly, cycle at weekends, and consider themselves reasonably active still find that their strength, their weight, and their joint health are moving in the wrong direction as they age.

What actually works: progressive resistance training

The research on this is clear and has been for decades. Progressive resistance training, which means lifting weights or using your body weight against resistance in a structured, incrementally challenging way, is the most effective intervention available for reversing sarcopenia.

It does not require training five days a week or lifting heavy weights from the start. The principle is simple. Give your muscles a reason to maintain and grow by asking them to work against resistance. Then give them a slightly bigger challenge over time so they continue to adapt. Two to three sessions per week of well-structured strength training is enough to make meaningful progress for most adults over 35.

The results are well-documented. Older adults who engage in regular resistance training show significant improvements in muscle mass, metabolic rate, joint stability, bone density, balance, and functional independence. People in their sixties and seventies who have never trained before can still build meaningful muscle. The body retains this capacity much longer than most people assume.

Protein matters more than you think

Exercise is only one part of the equation. Muscle is built from protein, and the efficiency with which your body uses dietary protein to build muscle also declines with age. Adults over 35 generally need more protein than younger adults to stimulate the same amount of muscle protein synthesis.

The commonly cited recommendation of 0.8 grams of protein per kilogram of bodyweight is based on the minimum needed to prevent deficiency, not the amount needed for an active adult trying to maintain or build muscle. Most exercise physiologists working with older adults recommend somewhere between 1.6 and 2.2 grams per kilogram of bodyweight per day, spread across meals rather than consumed all at once.

Practically, this means making sure there is a meaningful protein source at every meal. Eggs, meat, fish, Greek yogurt, legumes. Not obsessively tracking grams, but making it a consistent priority rather than an afterthought.

The long game

The reason muscle loss matters is not just about how you feel today. It is about what your body will be capable of in 20 or 30 years. The ability to get off the floor without using your hands, to carry your shopping, to walk up stairs without thinking about it, to stay independent and physically capable well into later life. These things depend directly on how much muscle you maintain and build in the decades leading up to them.

Starting at 35 or 40 or 50 is not too late. The research consistently shows that it is never too late to begin, and that even adults starting resistance training in their sixties and seventies see significant improvements. But starting earlier means more years of accumulated strength and health to draw on later.

At Motus, this is the lens through which all of our programming is designed. Not aesthetics, not performance benchmarks. Long-term physical capability for adults who want to stay strong, capable and independent as they age.