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Losing Muscle on GLP-1 Drugs: How to Protect It

Up to about two-fifths of weight lost on semaglutide in one trial was lean mass. Dr. Sayantan Banerjee explains what that means and how protein and strength training help.

OBESITY REMISSION

Dr. Sayantan Banerjee

10/31/20268 min read

When you lose weight, not all of it is fat. Some comes from lean tissue, which includes muscle. This happens with any kind of weight loss, whether from dieting, surgery or medication. GLP-1 medicines have made the question more urgent, because people lose so much weight, so quickly, and often eat very little while they do it.

You may have seen headlines about "Ozempic muscle loss" or worried that you are losing strength along with the weight. This article explains what the numbers show, why muscle matters, and the practical steps that protect it.

What lean mass means

Doctors usually divide body weight into fat mass and lean mass. Lean mass is everything that isn't fat: skeletal muscle, organs, bone, skin, connective tissue and water.

The most common way to measure body composition in trials is a DXA scan, the same type of low-dose X-ray used to measure bone density. DXA is accurate for fat, but its lean mass figure includes water and organs as well as muscle. So a fall in DXA lean mass isn't the same as an equal fall in muscle. Some of it is water, particularly early in weight loss, and some is the shrinking of organs such as the liver, which is often a good thing.

That said, some muscle is lost in most weight loss, and protecting it is worthwhile.

How much is lean mass?

In the STEP 1 trial of semaglutide 2.4 mg, a subgroup of participants had DXA scans before and after treatment. Fat mass fell by about 19% and lean mass by about 10%. Put another way, a bit under two-fifths of the weight lost was lean tissue.

In the SURMOUNT-1 trial of tirzepatide, the body-scan group lost fat and lean tissue at a ratio of roughly three to one. So about a quarter of the weight lost was lean.

These proportions are broadly similar to what is seen with diet-based weight loss and bariatric surgery. GLP-1 medicines aren't unusually bad for muscle. They simply produce more weight loss than most diets, so the absolute amount of lean tissue lost can be larger.

There is also context to remember. People with obesity carry extra muscle to move a heavier body around. When they lose weight, some reduction in muscle is expected and isn't necessarily harmful. What matters most is how much muscle you keep relative to your new body size, and how strong and functional you are.

Why muscle matters

Blood sugar. Muscle is the biggest site of glucose disposal after a meal. More muscle means more capacity to take up glucose, which matters a great deal for people with prediabetes or type 2 diabetes.

Metabolism. Muscle contributes to your resting energy use. Keeping it helps limit the slowdown in metabolism that follows weight loss.

Strength and independence. For anyone over 50, muscle strength is closely tied to balance, mobility and the risk of falls. Low muscle mass and strength in older age, called sarcopenia, is linked to poorer health outcomes.

Weight regain. If you stop the medicine and regain weight, the new weight tends to be more fat than muscle. Over several cycles of losing and regaining, body composition can gradually worsen, even if the scale ends up in the same place.

Who is most at risk

Some people need to be particularly careful:

adults over 60, who lose muscle more easily and regain it more slowly
people who were already inactive before starting
people who eat very little on treatment, especially very little protein
people with conditions that affect muscle, such as some chronic lung, kidney or heart conditions
people losing weight very quickly

If any of these apply, it is worth discussing a plan with your doctor or a dietitian before or soon after starting treatment.

Protein: eat enough, and spread it out

GLP-1 medicines reduce appetite a lot. Many people end up eating far less protein than they need, simply because they are eating less of everything.

Many obesity specialists suggest around 1.2 to 1.6 g of protein per kilogram of body weight a day during active weight loss, which is higher than the standard recommendation for adults. For a 100 kg (220 lb) person, that is 120 to 160 g a day. If you have kidney disease, ask your doctor first, because your target may be lower. Some specialists base the target on a lower adjusted weight for people with very high BMIs, so ask what applies to you.

A simpler approach that works for most people is to put protein first on the plate at every meal. Aim for 25 to 40 g each time. Some examples:

3 large eggs — Roughly how much protein: 18 g
150 g (5 oz) chicken breast, cooked — Roughly how much protein: 45 g
170 g pot of plain Greek yogurt (a US 6 oz cup) — Roughly how much protein: 15 to 17 g
200 g cottage cheese — Roughly how much protein: 20 to 24 g
1 tin (400 g) chickpeas, drained — Roughly how much protein: 15 to 18 g
150 g firm tofu — Roughly how much protein: 18 to 24 g
1 salmon fillet, about 125 g — Roughly how much protein: 25 g
1 glass (250 ml) of milk — Roughly how much protein: 8 g
A protein shake — Roughly how much protein: 20 to 30 g, check the label

If you can only manage small meals, which is common on these medicines, protein shakes, milk, yogurt drinks or soups with added beans or lentils can help close the gap. Eat the protein part of the meal first, before you feel full.

Spreading protein across the day seems to support muscle better than eating most of it at one meal. Three meals with a good portion each is a sensible pattern.

Strength training: the signal that keeps muscle

Protein supplies the building blocks. Resistance exercise is the signal that tells your body to keep and build muscle. Without it, extra protein does much less.

You don't need a gym. Two or three sessions a week of 20 to 40 minutes is enough to make a real difference. Work the big muscle groups:

legs and hips: sit-to-stand from a chair, squats, step-ups, lunges
chest and arms: push-ups against a wall or kitchen counter, moving lower as you get stronger
back: rows with a resistance band, or with a bag of shopping in each hand
shoulders: overhead presses with light dumbbells, water bottles or bands
core: wall planks or floor planks, and slow, controlled leg raises

Do 8 to 15 repetitions of each exercise for two or three sets. The last few repetitions should feel hard but possible with good form. Make it gradually harder every week or two, by adding repetitions, using a heavier band or weight, or adding a set.

If you have heart disease, joint problems, or haven't exercised in a long time, check with your doctor or a physiotherapist first. Many gyms and community centres offer beginner strength classes, and some NHS and US health systems run supervised exercise programmes.

Other things that help

Lose at a sensible pace. Very rapid weight loss tends to take more muscle with it. If you are losing more than about 1% of your body weight every week for many weeks, talk to your prescriber about whether the dose is right.

Keep walking. Daily steps protect overall fitness and help with blood sugar, even though they build little muscle on their own.

Get enough vitamin D and calcium. These matter for bone and muscle health, particularly in older adults and in the UK, where sunlight is limited in winter. NHS guidance suggests considering a vitamin D supplement in autumn and winter.

Sleep. Poor sleep makes it harder to build and keep muscle and increases hunger.

Limit alcohol. Heavy drinking interferes with muscle repair and adds calories.

Tracking something besides the scale

The scale can't tell you whether you are losing fat or muscle. Other measures help:

waist circumference, which mostly reflects fat
strength, such as how many push-ups or chair stands you can do in 30 seconds
grip strength, which some clinics measure
how easily you climb stairs or carry shopping
body composition scans, which some clinics offer

If your weight is falling and your strength is holding or improving, you are on the right track.

What about medicines to protect muscle?

Several companies are testing drugs designed to preserve muscle during weight loss, sometimes in combination with GLP-1 medicines. Some early results are interesting, but none is established in routine care yet. For now, protein and strength training remain the proven approach.

Bottom line

GLP-1 medicines are very effective, and losing some lean mass is part of losing a lot of weight. With enough protein and regular strength training, you can make sure most of what you lose is fat, and you can stay strong as you get lighter.

A high-protein day on a small appetite

One of the hardest parts of taking a GLP-1 medicine is eating enough protein when you barely feel hungry. Smaller, protein-first meals and snacks work better than trying to eat large plates. Here is one example, giving roughly 100 to 120 g of protein. Adjust portions to your own needs.

Breakfast: a 170 g pot of plain Greek yogurt with a spoon of nuts and some berries (about 20 g protein).
Mid-morning: a glass of milk or a small protein shake (about 10 to 25 g).
Lunch: two eggs or a small tin of tuna with salad and a slice of wholegrain bread (about 15 to 25 g).
Afternoon: a small pot of cottage cheese, or hummus with vegetable sticks (about 8 to 15 g).
Dinner: a palm-sized portion of chicken, fish or tofu with vegetables, eaten protein first (about 25 to 35 g).

A few tips make this easier. Eat the protein part of each meal first, before you feel full. Choose softer, moist protein foods if you have nausea, such as fish, eggs, yogurt and soups with beans or lentils. Keep easy options in the fridge so you don't have to cook when appetite is low. And if you are struggling to reach your target, a registered dietitian can help you build a plan that suits your tastes and any other health conditions.

Remember that very low intake for long periods can also mean missing vitamins and minerals. If you are eating very little, ask your doctor or dietitian whether a multivitamin is sensible for you.

How my book can help

The Obesity Exit Strategy covers exercise, food structure and where GLP-1 medicines fit into a longer plan. It explains why weight loss should be about losing fat while protecting your health, not just about the number on the scale. Find details on the book page.

Frequently asked questions

Does Ozempic cause muscle loss? It causes weight loss, and some of any weight loss is lean tissue. Protein and strength training reduce the share.

How much protein should I eat on Wegovy? Many specialists suggest about 1.2 to 1.6 g per kg of body weight daily, unless you have kidney disease.

Can I build muscle while on a GLP-1? Yes, especially if you are new to strength training, though it is harder while eating much less.

Is walking enough to protect muscle? Walking helps fitness and glucose, but resistance exercise is needed to protect muscle well.

Are protein shakes necessary? No, but they are a useful option when appetite is very low.

Is lean mass loss the same as muscle loss? Not exactly. DXA lean mass includes water and organs, so muscle loss is usually smaller than the lean mass figure.

How do I know if I'm losing too much muscle? Signs include feeling weaker, finding stairs or carrying shopping harder, and losing weight very fast. A strength test, such as counting chair stands in 30 seconds, or a body composition scan can help.

Should older adults be more careful? Yes. People over 60 lose muscle more easily, so protein and strength training are especially important. Discuss your plan with your doctor before or soon after starting.

When should I start strength training? Ideally as soon as you start the medicine, or even before, so the habit is in place while appetite falls.