GLP-1 Protein Calculator: How to Prevent Muscle Loss on Ozempic, Wegovy, and Zepbound

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

Most adults on a GLP-1 medication should aim for roughly 1.2 to 1.6 grams of protein per kilogram of body weight per day while actively losing weight. That is the range noted in the 2025 joint advisory on nutrition for GLP-1 therapy from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. A 2025 JAMA Internal Medicine patient guide gives a similar range of 1.0 to 1.5 g/kg for moderately active adults, with 20 to 30 grams at each meal.

There is one catch most protein calculators skip. The advisory notes there is no consensus on which body weight to use. For someone at 300 pounds, multiplying actual weight by 1.6 gives a number above 200 grams a day, which is unrealistic on a medication that shrinks your appetite. That is why this calculator uses an adjusted body weight when BMI is 30 or higher. It produces a target that protects muscle and that you can actually eat.

In practice, many people on semaglutide or tirzepatide land somewhere between 90 and 150 grams a day. Without a plan, most fall well short, because a smaller appetite cuts protein along with everything else.

How much muscle do you lose on Ozempic, Wegovy, or Zepbound?

In the major trials, a meaningful share of weight lost was lean mass:

In the SURMOUNT-1 body composition substudy, people on tirzepatide lost about a third of their fat mass and about 11% of their lean mass. Interestingly, the placebo group lost a similar 75% fat to 25% lean split, which matches what dieting alone usually produces. GLP-1 medications are not uniquely destructive to muscle. They simply cause a lot of weight loss, and any large weight loss without strength training and protein takes some lean tissue with it.

Lean mass is not the same as muscle

DXA scans report "lean mass," which includes water, organ tissue, and glycogen as well as skeletal muscle. Part of the lean mass lost during weight loss is expected and harmless, such as a liver that shrinks as it sheds fat. Muscle quality may even improve as fat stored inside muscle decreases. Still, real muscle loss does happen, and it matters most for people over 50, women after menopause, and anyone who wasn't training before starting the medication. Muscle is what keeps your metabolism, strength, and blood sugar control intact after you stop losing weight.

How to prevent muscle loss on a GLP-1 medication

The joint advisory identifies two levers that reduce lean mass loss: resistance training and adequate protein. Protein without training does relatively little, because muscle needs a reason to stay. Training without protein leaves the body without raw material. You need both.

Strength training: the minimum effective dose

You don't need to live in the gym. For most busy adults, this is enough to send a strong signal to keep muscle:

• Two full-body sessions per week, about 45 minutes each. Three is better if your schedule allows.
• Five or six compound movements per session: a squat or leg press, a hinge such as a Romanian deadlift, a horizontal push, a horizontal pull, an overhead or vertical press, and a vertical pull.
• Two or three hard sets per movement, ending each set with only one to three reps left in the tank.
• Add weight or reps over time. Progression is what tells your body the muscle is still needed.

Start on day one of your medication if possible, not after you've already lost 30 pounds.

Protein: hit the floor every day

Think of the lower number from the calculator as a floor you don't go below, and the higher number as the target on training days. Consistency matters more than precision.

How to eat enough protein when you have no appetite

This is the hardest part for most people on Ozempic or Zepbound. Strategies that work:

• Eat protein first. Start every meal with the protein portion before you fill up on anything else.
• Drink some of it. A protein shake or ultra-filtered milk can supply 25 to 40 grams with very little fullness.
• Choose dense sources: Greek yogurt, cottage cheese, egg whites, chicken breast, canned tuna or salmon, shrimp, lean beef, tofu, and tempeh.
• Eat smaller, more frequent meals. The joint advisory specifically supports this when hunger is low, and suggests setting reminders to eat.
• Watch dose-change weeks. Appetite often drops most right after a dose increase, which is when protein most easily slips.

Does the Wegovy pill or Foundayo cause less muscle loss?

The oral GLP-1s produce somewhat less average weight loss than the injections, so the absolute amount of lean tissue at stake is usually smaller. Detailed body composition data for the pills is still limited, but there is no reason to think the principles differ. The same protein targets and the same strength training plan apply. One practical difference: the Wegovy pill must be taken on an empty stomach with a small sip of water and a 30 minute wait before eating, so plan your first protein feeding for after that window. Foundayo has no food or water restrictions.

How this calculator works

For transparency, here is the method. If your BMI is under 30, protein is calculated from your actual weight. If it is 30 or higher, it uses an adjusted body weight: ideal body weight plus 40% of the difference between actual and ideal weight. The floor is 1.2 g/kg of that weight. The target is 1.4 g/kg, raised to 1.5 g/kg if you strength train at least twice a week, and by another 0.1 g/kg if you are 60 or older, up to 1.6 g/kg. Results are rounded to the nearest 5 grams.

Lean mass at stake is your projected weight loss (your goal weight, or the average from your medication's main trial) multiplied by 25% to 40%, the range seen in the semaglutide and tirzepatide body composition studies. It describes what happens without deliberate training and protein, not what has to happen to you.

Frequently asked questions

References

1. Mozaffarian D, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. Am J Clin Nutr. 2025;122(1):344-367. doi:10.1016/j.ajcnut.2025.04.023
2. Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med. 2021;384:989-1002.
3. Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med. 2022;387:205-216.
4. Look M, et al. Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study of adults with obesity or overweight. Diabetes Obes Metab. 2025.
5. Oral semaglutide at a dose of 25 mg in adults with overweight or obesity (OASIS 4). N Engl J Med. 2025.
6. Orforglipron, an oral small-molecule GLP-1 receptor agonist, for obesity treatment (ATTAIN-1). N Engl J Med. 2025.
7. Mehrtash F, Dushay J, Manson JE. Patient page on diet and physical activity with GLP-1 medications. JAMA Intern Med. 2025.

Written and medically reviewed by Mahiar Rabie, MD, internal medicine physician and founder of Arete Health. Last updated October 2026. This page is for education and does not establish a doctor-patient relationship.