On a GLP-1? The protein and lifting plan that helps protect your muscle

GLP-1 drugs such as semaglutide (Wegovy, Ozempic) and tirzepatide (Zepbound, Mounjaro) take weight off fast, and not all of it is fat. This guide covers what the trials measured, how much protein the nutrition societies recommend, and how to lift so more of the loss is fat. It is not prescribing advice: your dose, your medication and any medical condition are for the clinician who prescribes it.

Do GLP-1 drugs make you lose muscle?

Some, yes. Any large, fast weight loss takes lean tissue with it. The 2025 joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society lists muscle and bone loss among the main challenges of GLP-1 treatment. It says three things move the loss: how hard calories are cut, how fast the weight comes off, and whether you strength train. Only the last is fully in your hands.

How much of the weight lost is muscle?

Two trials measured it with DXA scans, the X-ray method that splits body weight into fat, lean tissue and bone.

• Semaglutide, STEP 1. The main trial enrolled 1,961 adults and randomized them 2:1 to 2.4 mg a week or placebo for 68 weeks; weight fell 14.9 percent versus 2.4 percent on placebo. For STEP 1 the joint advisory reports an average loss of 13.6 kg, of which 8.3 kg (62 percent) was fat and 5.3 kg (38 percent) lean mass. The SURMOUNT-1 body-composition paper describes the STEP 1 DXA substudy as roughly 60 percent fat and 40 percent lean.
• Tirzepatide, SURMOUNT-1. The main trial randomized 2,539 adults to 5, 10 or 15 mg a week or placebo for 72 weeks; weight fell 15.0, 19.5 and 20.9 percent versus 3.1 percent on placebo. In the 160-person DXA substudy, tirzepatide cut body weight 21.3 percent, fat mass 33.9 percent and lean mass 10.9 percent. About 75 percent of the loss was fat and 25 percent lean, in both the tirzepatide and the placebo groups, and the split held across age groups (76 percent fat in people 65 and older on the drug).

The American Council on Exercise summarizes the range as 25 to 40 percent of weight lost coming from lean mass. Two caveats apply.

First, lean mass is not the same thing as muscle. A 2024 review in Diabetes, Obesity and Metabolism points out that it also includes organs, bone, fluids and the water inside fat tissue, and that published lean-loss figures run from about 15 percent or less to as much as 40 to 60 percent of weight lost, depending on the study. The joint advisory estimates muscle at about half of lean mass, which puts STEP 1’s muscle loss near 20 percent of the weight lost.

Second, body composition still improves. A 2026 meta-analysis of seven randomized trials (821 patients) found GLP-1 drugs lowered lean mass by 1.74 kg versus placebo, while lean mass as a share of body weight rose 1.81 percentage points. You end up leaner in proportion but still lose tissue worth keeping.

How much protein do you need on a GLP-1?

The joint advisory lays out the ladder. The general adult allowance is 0.8 g per kg of body weight per day. Targets of 1.2 to 1.6 g/kg have been proposed during active weight loss, and during major weight loss the recommendation it cites is 1.2 to 2.0 g per kg of adjusted body weight. It also sets two guardrails: do not fall below 0.4 to 0.5 g/kg, and avoid staying above 2 g/kg for long periods. ACE’s summary for trainers working with clients on these drugs uses the same 1.2 to 2.0 g/kg range, depending on training status and goals.

The table does the arithmetic. Grams are per day.

Body weight used	1.2 g/kg	1.6 g/kg	2.0 g/kg
60 kg (132 lb)	72 g	96 g	120 g
70 kg (154 lb)	84 g	112 g	140 g
80 kg (176 lb)	96 g	128 g	160 g
90 kg (198 lb)	108 g	144 g	180 g
100 kg (220 lb)	120 g	160 g	200 g
110 kg (243 lb)	132 g	176 g	220 g
120 kg (265 lb)	144 g	192 g	240 g

Which weight goes in the first column matters. The advisory warns that using actual weight in people with obesity can significantly overestimate protein needs, and it offers two ways around that: 1.5 g per kg of fat-free mass if you have a body-composition scan, or a flat 80 to 120 g a day, which it says may be easier to stick with. If your current weight is far above where you are heading, start with the flat range and ask your clinician or a registered dietitian to calculate an adjusted weight. If you have kidney disease, ask before raising protein at all.

For the general case (how much per meal, and whey versus plant protein), see the protein guide.

How do you hit a protein target when you are not hungry?

Low appetite is the point of these drugs, which is why protein slips. The advisory’s suggestions:

• Eat the protein first in each meal, so it is not what gets left on the plate.
• Pick low-volume protein foods. It names fish, eggs, Greek yogurt, cottage cheese, and nuts and seeds, including peanut and almond butter.
• Use shakes or bars if food falls short. It lists them as a way some people meet their targets.
• If nausea stops you eating, eat breakfast and then small meals every 3 to 4 hours with plenty of fluid. Severe nausea, vomiting or diarrhea can dehydrate you enough to injure the kidneys, so tell your prescriber if you cannot keep food or fluids down.

A worked example: at 90 kg and 1.2 g/kg, the target is 108 g, which is four servings of about 27 g spread across the day.

How often should you lift weights on a GLP-1?

The joint advisory is direct that more protein alone is likely not enough to keep muscle without structured resistance training. It says resistance or mixed resistance-plus-aerobic programs are well established to help preserve lean mass during weight loss, and that aerobic activity alone has a smaller effect.

The joint advisory aims for strength training at least 3 times a week plus at least 150 minutes of moderate aerobic exercise. As a floor for every adult, the HHS Physical Activity Guidelines ask for muscle-strengthening activity at least 2 days a week, on top of 150 to 300 minutes of moderate aerobic activity. The ACSM position stand on resistance training recommends 2 to 3 days a week for beginners, with loads you can lift 8 to 12 times.

The best test of what that does during a diet is the LITOE trial (Villareal et al., NEJM, 2017). It randomized 160 adults 65 and older with obesity into four groups of 40: a control group with no diet or exercise, and three groups that dieted (500 to 750 fewer calories a day with about 1 g/kg of protein) and added aerobic training, resistance training, or both, in three supervised sessions a week for six months. The lifting was nine machine exercises, starting at 1 to 2 sets of 8 to 12 reps. Every exercise group lost about 9 percent of body weight. Lean mass fell 2.7 kg with aerobic training, 1.7 kg with combined training and 1.0 kg with resistance training, and strength rose 19 percent in the lifting group against 4 percent in the aerobic group. It was not a GLP-1 trial and the loss was smaller than on the drugs, but it shows lifting changes what the lost weight is made of.

A starter plan: three days a week, machines are fine

This mirrors the LITOE program and the ACSM beginner guidance. Run it on three non-consecutive days, the advisory’s target, or two if that is what your week allows.

1. Legs: leg press or goblet squat.
2. Hip hinge: dumbbell Romanian deadlift or back extension.
3. Push: chest press machine or push-ups.
4. Pull: seated row or lat pulldown.
5. Overhead: shoulder press machine.
6. Carry: farmer’s carry with dumbbells.

Start with 1 to 2 sets of 8 to 12 reps and build to 2 to 3 sets, the way the trial did. When you can do one or two reps more than your target number at the current load, add 2 to 10 percent to the load, which is ACSM’s progression rule. Walk on the other days. If a dose increase leaves you dizzy or unable to eat before training, tell your prescriber rather than pushing through. The full guideline week is laid out in how much exercise you actually need.

Is protein powder worth it on a GLP-1?

As food, yes. A scoop of whey isolate is a low-volume way to add protein when a full plate will not go down. It is not a treatment and does not replace the lifting above. On 09/29/2026, Transparent Labs Grass-Fed Whey Protein Isolate listed 28 g of protein per serving and Legion Whey+ listed 22 g. Pick one with published third-party testing, and read supplements that actually work before adding anything else.

When to talk to your prescriber

• Before changing, pausing or stopping your dose for any reason.
• If you have kidney disease, or a history of kidney stones; the advisory says people with kidney stones should be counseled to avoid high-oxalate foods, highly processed foods and animal-source proteins.
• If nausea or vomiting keeps you from eating or drinking.
• If you are 65 or older or already have low muscle. The advisory recommends a baseline exam that includes muscle strength, function and body composition, which is a reasonable thing to ask for.

Where to buy / how to save

Prices and offers below were read on each brand’s own site on 09/29/2026.

• Transparent Labs is the higher-protein scoop of the two (28 g against Legion’s 22 g). Subscribe & Save takes 10 percent off plus free shipping, which put the 2 lb whey isolate at $58.49 instead of $64.99. One-time U.S. orders ship free over $99.
• Legion Athletics is the pick if you want to try a tub first. Its own save-20 page prints the code FIRSTTIME for 20 percent off a first order, and Subscribe & Save takes 30 percent off the first shipment and 15 percent off every one after. U.S. orders over $80 ship free.
• Planet Fitness is the low-cost way to a room full of the machines in the plan above. Classic starts at $15 a month and PF Black Card at $24.99, plus taxes, a startup fee that varies by club, and a $49 annual fee; some locations require a 12-month commitment and prices vary by club, so open your own club’s page before joining.

Each brand’s deal page, linked above, lists every verified offer with its terms and the date it was checked.