In short
- Slow decline is normal. Months are not. Noticeable loss over a few months deserves investigation.
- Intake is the first suspect. Too little protein or too little total energy for your training load explains most of it.
- Weight loss medication is a common modern cause. Close to a third of the weight lost on GLP-1 medicines comes from muscle related measures.
- Testosterone does build muscle, but only where deficiency is genuine, and it is not the usual cause.
- Measured, not estimated. Body composition and strength recorded, so change can be tracked.
Condition Overview
What is normal and what is not
Skeletal muscle declines slowly from around the fourth decade. That is expected and it is gradual.
A noticeable loss over a few months is not normal ageing. Neither is losing strength on familiar lifts while training consistently.
What men notice first
- Reduced strength on lifts you know well.
- Softer definition, particularly in the arms and shoulders.
- Fatiguing earlier on stairs or carrying.
- Weight staying stable while the shape of the body changes towards fat.
That last point is why the scale is useless here. Losing four kilograms of muscle and gaining four of fat shows as no change at all.
The causes, in rough order of frequency
| Cause | How it shows |
|---|---|
| Too little protein or total energy | Training unchanged, intake dropped, often during a diet |
| Unstructured or absent resistance training | Cardio maintained, strength work quietly dropped |
| Rapid weight loss, including on GLP-1 medicines | Fast loss with no protein or training plan alongside |
| Poorly controlled diabetes | Muscle loss with thirst, fatigue and central weight |
| Thyroid disease | Weakness with weight and temperature change |
| Corticosteroids | Proximal weakness, worse in the thighs and shoulders |
| Chronic illness or inflammation | Loss alongside other systemic symptoms |
| Testosterone deficiency | Muscle loss with low libido and fewer morning erections, over a year or more |
The GLP-1 point
This has become one of the most common causes seen in practice, and it is largely avoidable.
Across studies of GLP-1 based weight medicines, close to a third of the weight lost came from muscle related measures. Where nobody set a protein target or a resistance training plan, that is what happens.
Losing muscle also lowers resting energy expenditure, which makes weight regain more likely afterwards. So it is not only a strength problem.
Where testosterone fits
Testosterone replacement does produce substantial gains in muscle mass and strength, but only where genuine deficiency is confirmed by symptoms and repeated low morning levels.
Muscle loss on its own, without low libido or fewer morning erections, is a weak reason to suspect it, and treating a normal man for it carries risk without benefit.
When to See a Doctor
- Your strength on familiar exercises has fallen over a few months while your training has stayed the same.
- Your weight has held steady but your body composition has clearly moved from muscle towards fat.
- Muscle loss has appeared alongside reduced libido, poor recovery or persistent tiredness.
- You take, or have recently taken, corticosteroids, or you have a chronic condition that could explain the change.
- You are losing weight without trying, which requires prompt investigation before anything is attributed to hormones or training.
- Weakness is concentrated in one limb or one muscle group, or you have numbness or twitching, which needs neurological assessment.
- You have difficulty swallowing, breathlessness at rest or trouble rising from a chair, which need urgent medical review.
How Dr. Felix Assesses This
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1
Training and intake history
Dr. Felix goes through what you actually lift, how often, with what progression, and what you eat on a typical day including protein distribution and total energy. A great deal of unexplained muscle loss is explained here before any test is ordered.
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2
Medical and drug review
Chronic illness, recent infections, corticosteroid or immunosuppressant use, alcohol intake, previous anabolic steroid cycles, gastrointestinal symptoms and any unintended weight change are documented. Injuries and periods of enforced rest are noted, since disuse loss is rapid and often underestimated.
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3
Measurement and testing
Body composition, weight, waist and grip strength are measured so future comparison is possible. Blood tests cover full blood count, ferritin, thyroid function, HbA1c, kidney and liver function, calcium, vitamin D, inflammatory markers and morning testosterone repeated on a second morning if it is low.
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4
Diagnosis and plan
Dr. Felix explains which factors are responsible and in what proportion. The written plan sets protein and energy targets, a resistance training structure, treatment of any medical cause found and a measurement date to check that muscle is returning.
Treatment Options
Men’s Hormone Optimization
Why one hormone is not enough Testosterone does not operate alone, and a single number rarely explains a man who…
View Treatment
Men’s Performance Program
The problem this solves Fragmentation. Most men have a trainer for one part, an app for another and no physician…
View Treatment
TRT Consultation
What this appointment is for Testosterone deficiency needs two things at once: symptoms consistent with it, and a genuinely low…
View Treatment
Why Early Treatment Can Matter
Muscle responds well to correction, but it rebuilds more slowly than it disappears. Acting while the loss is recent means shorter work to recover it and less compensatory change in body fat and blood sugar control.
Muscle also does more than move you. It is the largest site of glucose disposal in the body, so preserving it supports metabolic health and, later in life, balance and independence. A structured performance programme puts training, nutrition and any medical treatment into one plan rather than three separate efforts.
Why Early Treatment Can Matter
Muscle responds well to correction, but it rebuilds more slowly than it disappears. Acting while the loss is recent means shorter work to recover it and less compensatory change in body fat and blood sugar control.
Muscle also does more than move you. It is the largest site of glucose disposal in the body, so preserving it supports metabolic health and, later in life, balance and independence. A structured performance programme puts training, nutrition and any medical treatment into one plan rather than three separate efforts.
Recent loss rebuilds faster
Muscle regained through training returns more readily when the loss is new.
Metabolic and functional cost
Less muscle means poorer glucose handling and reduced strength with age.
Measure, then decide
Body composition and grip strength give an objective starting point to compare against.
Cost & Consultation Investment
This assessment is charged as physician time, covering the training and dietary history, examination, body composition measurement, choice and interpretation of investigations and the written plan you leave with. Laboratory tests are invoiced by the laboratory, and any prescribed treatment is separate. Ongoing supervision while you rebuild is usually arranged as a programme or membership. Current details appear on the pricing page.
Frequently Asked Questions
A slow decline from around the fourth decade is normal. A noticeable loss over a few months, or losing strength on familiar lifts while training consistently, is not, and it deserves investigation.
It is set to your body weight and given as a number in grams, not as advice to eat more protein. That number goes up, not down, during any weight loss phase.
Probably some. Across studies of GLP-1 medicines close to a third of the weight lost came from muscle related measures. Whether that happened to you is answered by measuring body composition rather than guessing.
Because muscle is where glucose goes and it drives your resting energy expenditure. Losing it makes weight regain more likely and glucose handling worse, quite apart from being weaker.
Only if you have genuine deficiency confirmed by symptoms and repeated low morning levels. Testosterone does increase muscle mass and strength substantially in that group. In men with normal levels it is not treatment and carries real risk.
No. Aerobic training has its own clear benefits and does not protect muscle. Resistance work at least twice a week is what does.
Because the scale cannot distinguish muscle from fat. Losing four kilograms of muscle while gaining four of fat shows as no change at all, which is exactly why body composition is measured here.
Corticosteroids are the classic cause and produce weakness that is worse in the thighs and shoulders. Your full medication list is reviewed at the first appointment.
Months rather than weeks, and slower than it was lost. Progress is judged on repeat body composition and strength markers at three monthly intervals rather than on how you feel.
It depends on the investigations needed, so a single figure would be misleading. You get the full cost in the consultation before anything is arranged.
Evidence
Where this information comes from
Every figure on this page is taken from the sources below. All of them are free to read, so you can check them yourself.
This page is general medical information and does not replace a personal consultation. Trial results are averages across large groups, not a prediction for any one person.