Losing Muscle on a GLP-1? Protein, Strength Training and 3 Ways to Check

On a GLP-1 like Zepbound or Wegovy, part of the weight you lose is lean tissue, which includes muscle. That happens with any weight loss, with or without the drug. Eating about 1.2 to 1.6 grams of protein per kilogram of body weight a day, strength training about three times a week, and measuring what your weight is made of are the best ways to hold on to muscle. The scale can’t tell you whether you’re losing fat or muscle. A few simple checks can.

How much of the loss is muscle?

In the body-scan studies, about one pound in four of the weight lost on tirzepatide (Zepbound) was lean mass, and closer to four in ten on semaglutide (Wegovy). Not all lean mass is muscle: it also counts water and organs. In a tirzepatide trial, the share of lean tissue lost was about the same as in people who lost weight on the same program without the drug. So the loss comes from losing weight, not from the medicine itself. That’s good news, because it’s the part you can do something about.

Three ways to check what you’re losing

• A DEXA scan. It’s the real measure of what your weight is made of: fat, lean mass and bone, plus visceral fat, the fat around your organs that drives insulin resistance and heart risk. You can have a normal BMI and still carry too much of it. Get a scan at the start and repeat it, so you’re comparing you to you. Ask for body composition, not just bone density, because not every scan center offers it.
• Grip strength. A hand grip meter is cheap. Use the same hand once a month. If that number keeps sliding while the scale goes down, bring it to your doctor.
• Your own strength. Stand up from a chair five times without using your hands. If that gets harder month to month, pay attention. If you lift, keep a log: weights going down is a signal.

How much protein

While you’re losing weight, aim for about 1.2 to 1.6 grams of protein per kilogram of body weight a day. For many adults that’s roughly 90 to 120 grams. You may have seen headlines saying less protein helps you live longer. Those studies looked at mostly sedentary people who weren’t losing weight. If you’re in a calorie deficit, on a GLP-1, or training, protein matters more, not less.

One exception: your kidneys. About 14% of American adults have chronic kidney disease, and about 87% of them don’t know it. A normal blood panel doesn’t rule it out; it takes a urine test (a urine albumin check). If your kidneys are struggling, more protein isn’t automatically better, so ask your doctor before raising it.

What to eat when your appetite is small

On a GLP-1, every bite has to count. The best foods are high in protein, easy to tolerate, and worth the room they take up:

Food	Why it works or doesn’t
Plain Greek yogurt	High in protein, cold, soft and easy to eat, with calcium. Hard to beat.
Protein shake	An easy 20 to 30 grams when appetite is low; cold and often easier to tolerate.
Chicken breast	Lean and protein-dense, though dry chicken can be hard to get down when you’re queasy.
Avocado, beef jerky	Fine in small portions. Higher-fat food can worsen fullness and nausea; jerky is salty and processed.
A big salad	Fills you up fast without much protein. Add a protein source.
Croissant	Little protein for a lot of calories; it uses up room you don’t have.

None of these foods is bad in itself. They’re ranked for someone on a GLP-1, where protein, nutrients per bite and tolerance matter most. Many people also fall short on fiber (about 30 grams a day is a good target) and on vitamins and minerals when they eat much less, which is worth raising with your doctor.

Strength training

Protein alone isn’t enough. Muscle is kept by using it: resistance training about three times a week is the other half. Muscle also matters beyond strength. It improves how your body handles insulin and raises the calories you burn at rest.

Sources

• Look et al., Diabetes, Obesity and Metabolism, 2025: SURMOUNT-1 body-composition (DEXA) substudy, lean mass about 25% of weight lost on tirzepatide
• Wilding et al., New England Journal of Medicine, 2021 (STEP 1) and its DEXA substudy: lean mass 38.6–40% of weight lost on semaglutide
• American Diabetes Association, Standards of Care in Overweight and Obesity, 2026: protein 1.2–1.6 g/kg/day during weight loss; grip-strength and chair-stand checks
• Joint advisory on nutrition with GLP-1 therapy (ACLM, ASN, OMA, TOS), 2025: DEXA monitoring and resistance training three times a week
• CDC, Chronic Kidney Disease in the United States: how common it is and how many people don’t know