Protein and Muscle on GLP-1 Medications: How Much You Need and How to Keep It

On semaglutide (Ozempic, Wegovy) or tirzepatide (Zepbound, Mounjaro), you lose some muscle along with fat: in the trials, between a quarter and a little over a third of the weight lost was lean mass. The best-supported way to limit it is to pair enough protein, 1.2 to 1.6 g per kilogram of body weight a day (0.54 to 0.73 g per pound) while you’re losing weight, with strength training at least two days a week. With a small appetite, the key is to spread protein across small meals and start each meal with it.

You can run your own numbers with the protein calculator (in Spanish; it works in kilograms, so divide your weight in pounds by 2.2). The big picture of eating during treatment is in my guide to what to eat on GLP-1 medications. Here I focus on muscle.

How much muscle you lose on semaglutide and tirzepatide

I went through the body-composition analyses of the two main trials, STEP 1 and SURMOUNT-1. Both measured a subgroup with DXA (dual-energy X-ray absorptiometry, a scan that separates fat, lean mass and bone). Lean mass includes muscle, but also organs, water and other fat-free tissue.

Study	Who	Weight	Fat mass	Lean mass	Share of weight lost that was lean mass
STEP 1, semaglutide, 68 weeks	140 adults without diabetes, 76% women	−15.0%	−19.3%	−9.7%	38% (5.3 of 13.6 kg, or 11.7 of 30 lb)
SURMOUNT-1, tirzepatide, 72 weeks	160 adults without diabetes, 73% women	−21.3%	−33.9%	−10.9%	About 25%

Sources: Wilding (2021) and Look (2025); the STEP 1 kilograms come from the 2025 joint advisory.

Three nuances:

• Lean mass isn’t the same as muscle. The 2025 advisory from four US obesity, nutrition and lifestyle-medicine societies (I’ll call it “the advisory”) estimates that muscle is about half of lean mass. In STEP 1, that puts muscle at around 20% of the weight lost.
• The share of lean mass goes up. In STEP 1, lean mass fell in pounds, but its share of body weight rose 3.0 percentage points because so much more fat was lost. In SURMOUNT-1, the placebo group lost weight in the same proportion as the tirzepatide group: three-quarters fat, one-quarter lean mass.
• The numbers vary between studies. The review by Neeland and colleagues (2024) collects GLP-1 studies where lean mass made up 40% to 60% of the weight lost, and others where it was 15% or less.

Why keeping muscle matters

Losing some lean mass when you lose weight is expected. Losing too much has three costs:

• Physical function. The PROT-AGE group, experts in protein and aging, points out that in older adults, losing physical capacity predicts dependence, falls and even mortality.
• Resting energy use. The authors of the STEP 1 analysis note that less muscle mass can affect resting energy expenditure and physical function.
• What comes back if the weight returns. In 78 postmenopausal women who lost weight without these drugs, every pound of fat lost came with 0.26 lb of lean mass lost. For every pound of fat regained the following year, only 0.12 lb of lean mass came back (Beavers, 2011). The advisory warns that these cycles may raise the risk of sarcopenic obesity (low muscle alongside excess fat). I explain the regain side in what happens when you stop Ozempic, Wegovy or Zepbound.

That said, there’s no reason for alarm. Neeland concludes that the muscle changes on these drugs look adaptive: the drop in muscle volume is what you’d expect for the weight lost, and muscle quality probably improves. In STEP 1, participants’ self-reported physical function improved more on semaglutide than on placebo. Still, older age and more severe disease can raise the risk of sarcopenia.

How much protein you need

Situation	Reference per day	Source
Adults in general	0.8 g/kg (0.36 g/lb)	US Recommended Dietary Allowance (National Academies); also used by the advisory
Active weight loss	1.2 to 1.6 g/kg (0.54 to 0.73 g/lb)	Leidy (2015); also in the advisory
Alternative that skips the per-pound math	80 to 120 g	The advisory
Healthy adults over 65	At least 1.0 to 1.2 g/kg (0.45 to 0.54 g/lb)	PROT-AGE (2013) and ESPEN (2014)
Active adults over 65	1.2 g/kg or more (0.54 g/lb or more)	PROT-AGE
Adults over 65 with an acute or chronic illness	1.2 to 1.5 g/kg (0.54 to 0.68 g/lb)	PROT-AGE and ESPEN

An example: for someone who weighs 154 lb (70 kg), the weight-loss range works out to 84 to 112 g a day. If you’re also over 65, the general reference is 70 to 84 g.

According to the advisory, protein shouldn’t drop below 0.4 to 0.5 g/kg (0.18 to 0.23 g/lb), and a prolonged intake of 2 g/kg (0.9 g/lb) or more is best avoided. It’s also unclear which weight to use in people with obesity, because current weight may overestimate what you need.

Per meal, Leidy and colleagues suggest at least 25 to 30 g, though cautiously (they say “potentially”). The International Society of Sports Nutrition (ISSN), which writes for people who exercise, puts the amount per serving at 20 to 40 g, or 0.25 g per kilogram, spread every 3 to 4 hours. The daily total is the reference all these sources agree on.

How to reach your target with very little appetite

The advisory offers three practical ideas:

• Start the meal with the protein. If you fill up halfway through, that part is already in.
• Choose foods that are small in volume and high in nutrients: fish, eggs, Greek yogurt, cottage cheese, nuts or nut butters.
• Turn to shakes, bars or protein-fortified foods if food alone doesn’t get you there. Protein powder is one of those options; the ISSN considers it, for active people, a practical way to add protein with few calories. Talk to your prescriber or a registered dietitian first.

If nausea is what’s holding you back, my guide to nausea on GLP-1 medications has small meals that go down easier. And since the advisory warns that very high-protein or high-fat meals can make constipation worse, my guide to constipation on GLP-1 medications covers the fluids and fiber that balance them.

Six small meals: an example with more than 100 g

Protein is calculated from the food pages (in Spanish), which use USDA data. Meat, fish and vegetables are weighed raw; rice and potato, cooked. Cup measures are approximate. This shows one way to spread protein, not a calorie plan: it leaves out cooking oil and whatever you add as your hunger allows.

Meal	What	Protein
Breakfast	2% cottage cheese (150 g, about ⅔ cup) with strawberries (100 g, about ⅔ cup)	16.3 g
Mid-morning	Whole-wheat bread (30 g, one slice) with an egg (55 g) and deli ham (30 g, 1 oz)	15.6 g
Lunch	Chicken breast (100 g, 3.5 oz), white rice (80 g, about ½ cup) and zucchini (100 g, about ¾ cup)	25.9 g
Afternoon snack	Smoothie with skim milk (200 ml, about 7 fl oz), plain Greek yogurt (100 g, a scant ½ cup) and banana (60 g, about half a small one)	16.8 g
Dinner	Cod (120 g, 4.2 oz) with boiled potato (100 g, 3.5 oz)	23.2 g
Before bed, if you want it	Part-skim ricotta (100 g, a scant ½ cup) with a kiwifruit (100 g)	12.5 g
Total		110.3 g

For someone who weighs 154 lb (70 kg), that lands near the top of the 1.2 to 1.6 g/kg range. Lunch and dinner each bring about 25 g; the smaller meals add up. If one of them doesn’t sit well, don’t force it.

The 15 foods with the most protein per serving

Ranked by protein in the typical serving from our database; meat and fish are weighed raw, beans and lentils cooked. The higher the last column, the more protein each bite brings, which helps when your appetite is small.

Food	Serving	Protein	Protein per 100 kcal
Chicken breast, skinless	150 g (5.3 oz)	33.8 g	18.8 g
Turkey breast, skinless	125 g (4.4 oz)	29.6 g	20.8 g
Lean beef (top round)	125 g (4.4 oz)	29.5 g	19.0 g
Atlantic cod	150 g (5.3 oz)	26.7 g	21.7 g
Pork tenderloin	125 g (4.4 oz)	26.3 g	19.3 g
Atlantic salmon, farmed	125 g (4.4 oz)	25.5 g	9.8 g
Chicken thigh, skinless	120 g (4.2 oz)	23.6 g	16.3 g
Atlantic mackerel	120 g (4.2 oz)	22.3 g	9.1 g
Light tuna, canned in water, drained	60 g (2.1 oz)	15.3 g	22.0 g
Sardines, canned in oil, drained	60 g (2.1 oz)	14.8 g	11.8 g
White beans, cooked	150 g (a scant cup)	14.6 g	7.0 g
Lentils, cooked	150 g (about ¾ cup)	13.5 g	7.8 g
Pinto beans, cooked	150 g (a scant cup)	13.5 g	6.3 g
Chickpeas (garbanzo beans), cooked	150 g (a scant cup)	13.3 g	5.4 g
Black beans, cooked	150 g (a scant cup)	13.3 g	6.7 g

Composition data: USDA FoodData Central. The full list, with dairy and eggs, is on the high-protein foods page (in Spanish).

Strength training: the other half

The advisory is clear: more protein without strength training probably isn’t enough to keep muscle. Research on weight loss in general backs this up:

• Sardeli meta-analysis (2018). Across six trials in older adults with obesity on a reduced-calorie diet, strength training three times a week for 12 to 24 weeks prevented 93.5% of the lean-mass loss caused by the diet.
• Villareal trial (2017). In 160 older adults with obesity, the groups that dieted and exercised lost 9% of their weight in 6 months. Lean mass fell 5% with aerobic exercise alone, 3% with aerobic plus strength training, and 2% with strength training alone.

With semaglutide or tirzepatide, direct evidence is still thin: the advisory mostly cites retrospective studies.

As a general reference, the World Health Organization recommends muscle-strengthening activities on 2 or more days a week for adults, at moderate or greater intensity and working all major muscle groups. It also recommends 150 to 300 minutes a week of moderate aerobic activity. For adults over 65, it adds varied activity that emphasizes balance and strength on 3 or more days a week. For people on GLP-1 medications, the advisory suggests strength training at least three times a week.

It doesn’t have to happen in a gym: resistance bands, dumbbells or your own body weight all count if you make them gradually harder. If you have heart disease, joint problems or another condition, check with your doctor before you start.

Sleep counts too

In a small trial, 10 adults with overweight followed a reduced-calorie diet for 14 days, sleeping either 8.5 or 5.5 hours a night. On less sleep, they lost 0.6 kg (1.3 lb) of fat instead of 1.4 kg (3.1 lb), and 2.4 kg (5.3 lb) of fat-free mass instead of 1.5 kg (3.3 lb) (Nedeltcheva, 2010). It’s a short study, but the advisory also includes sleep in the initial assessment for people starting a GLP-1.

When to get professional help

Talk to your doctor or a registered dietitian before raising your protein or starting to train if:

• You’re over 65, or it’s hard to get up from a chair or climb stairs. The advisory recommends assessing strength, function and body composition when treatment starts.
• You have risk factors for sarcopenia (loss of muscle mass and strength). The advisory lists older age, perimenopause or menopause, low testosterone, a sedentary lifestyle and no strength training.
• You have kidney disease. The KDIGO 2024 guideline suggests 0.8 g/kg a day in chronic kidney disease stages 3 to 5, and not going above 1.3 g/kg (0.59 g/lb) in adults at risk of progression. PROT-AGE excludes people with an estimated glomerular filtration rate below 30 who aren’t on dialysis from its figures. And the US Wegovy label reports postmarketing cases of acute kidney injury, some requiring hemodialysis, most of them in people whose nausea, vomiting or diarrhea led to dehydration.
• You’ve had kidney stones. The advisory suggests that people with kidney stones avoid animal protein, among other foods.
• You can’t eat enough for weeks at a time, or you have a history of eating disorders.

Frequently asked questions

Do GLP-1 medications make you lose muscle?

Some lean mass, as with any significant weight loss: about 25% of the weight lost in SURMOUNT-1 and 38% in STEP 1, and not all of it is muscle. Enough protein plus strength training is the combination with the most support for limiting it.

Should I calculate protein from my current weight?

There’s no consensus: with obesity, current weight may overestimate your needs. As an alternative, the advisory offers a fixed target of 80 to 120 g a day. The protein calculator (in Spanish) explains the approach I use.

Do I need protein shakes?

Not necessarily. The advisory mentions them, along with bars and fortified foods, as an option for people who can’t reach their target with food. Check with your prescriber or a registered dietitian first, especially if you have kidney disease.

Do I have to go to a gym?

No. The WHO asks for work on all major muscle groups on 2 or more days a week, without specifying where, and the advisory includes programs with a trainer, in a class or on your own.

Is eating a lot of protein dangerous?

The advisory recommends avoiding a prolonged intake of 2 g/kg (0.9 g/lb) a day or more, and KDIGO 2024 not going above 1.3 g/kg in chronic kidney disease with a risk of progression. For your own situation, talk to your doctor.