Evidence library

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

Protein is the most-pushed piece of GLP-1 advice, and much of the research behind the numbers is industry-funded. Here is what holds up: roughly how much to aim for, why the target depends on which body weight you use, and the limits of "more is better".

How to read these grades

Evidence strength

  • Strong evidence (does / reduces / improves)
  • Moderate evidence (probably / likely)
  • Early / weak evidence (may / might)

Tested in GLP-1 users?

  • Tested in GLP-1 users
  • Not tested in GLP-1 users
  • Trial underway

Aim higher on protein while losing weight: about 80 to 120 grams a day

Moderate evidence Not tested in GLP-1 users

During active weight loss, a higher protein intake, roughly 1.2 to 1.6 g per kg of body weight or a practical 80 to 120 g a day, probably helps preserve muscle and curb hunger. The targets come from non-GLP-1, largely industry-funded research, so read them as a reasonable aim, not a proven GLP-1 number.

What it rests on

  • Grosicki 2024 1

    A review setting protein targets for people losing weight on the newer obesity drugs. It suggests at least 1.2 g of protein per kg of body weight, or a practical 80 to 120 g a day, to help preserve muscle. All nine authors are tied to a weight-loss-meal company.

    Review, not a GLP-1 trial (industry-funded)

  • Leidy 2015 2

    A review of protein's role in weight loss, from a meat-and-dairy-industry protein summit. Higher protein (about 1.2 to 1.6 g/kg, 25 to 30 g per meal) modestly improved fat loss and muscle retention in the short term, with weaker evidence past a year.

    Review, not GLP-1 (industry-funded)

  • Mozaffarian 2025 advisory 3

    A joint advisory from four medical societies summarizing current best practice for supporting people on GLP-1s. It is an expert consensus document, not a trial, and is the standard reference for what the field recommends and where evidence is still missing.

    Four-society expert consensus

The target depends on which body weight you use

Moderate evidence Not tested in GLP-1 users

Protein need tracks lean tissue, not fat, so targets should be figured on an adjusted or reference weight rather than actual weight. Using actual body weight can overstate the target by around 100 grams a day in someone with obesity.

What it rests on

  • Volek 2024 4

    A review arguing protein targets should be based on a lean-tissue reference weight rather than actual body weight. Its worked example shows using actual weight can overstate the target by about 100 g a day in someone with obesity. The lead author has low-carb-industry ties.

    Review, not GLP-1 (industry ties)

  • Mozaffarian 2025 advisory 3

    A joint advisory from four medical societies summarizing current best practice for supporting people on GLP-1s. It is an expert consensus document, not a trial, and is the standard reference for what the field recommends and where evidence is still missing.

    Four-society expert consensus

There is a floor and a ceiling on protein

Moderate evidence Not tested in GLP-1 users

Too little protein, below roughly 0.4 to 0.5 g per kg a day, risks muscle loss, while sitting at or above about 2.0 g per kg long-term is probably not worth it. The specific figures rest on a primary paper still being sourced, so treat them as directional for now.

What it rests on

  • Mozaffarian 2025 advisory 3

    A joint advisory from four medical societies summarizing current best practice for supporting people on GLP-1s. It is an expert consensus document, not a trial, and is the standard reference for what the field recommends and where evidence is still missing.

    Four-society expert consensus

More protein is not always better

Early / weak evidence Not tested in GLP-1 users

Eating protein well past what muscle needs may offer no extra benefit and might be routed toward fat. This is a mechanism seen in a nine-person single-meal study, not a proven outcome, so it is a caution against chasing ever-higher protein, not evidence that protein makes you fat.

What it rests on

  • Charidemou 2019 5

    A small crossover study in nine healthy lean young men measured what a single high-protein meal did to fat metabolism. It raised a marker of fat production in the liver. It did not measure body fat, weight, or anything in people on GLP-1s.

    9 healthy men, single meal

  • Mozaffarian 2025 advisory 3

    A joint advisory from four medical societies summarizing current best practice for supporting people on GLP-1s. It is an expert consensus document, not a trial, and is the standard reference for what the field recommends and where evidence is still missing.

    Four-society expert consensus

Protein alone is not enough without resistance training

Expert consensus Mixed / consensus

Clinicians emphasize that protein feeds muscle but training is what builds and protects it, so protein on its own is probably not enough. This is expert consensus, the same "training first, protein second" order seen in the muscle evidence.

What it rests on

  • Mozaffarian 2025 advisory 3

    A joint advisory from four medical societies summarizing current best practice for supporting people on GLP-1s. It is an expert consensus document, not a trial, and is the standard reference for what the field recommends and where evidence is still missing.

    Four-society expert consensus

  • Leidy 2015 2

    A review of protein's role in weight loss, from a meat-and-dairy-industry protein summit. Higher protein (about 1.2 to 1.6 g/kg, 25 to 30 g per meal) modestly improved fat loss and muscle retention in the short term, with weaker evidence past a year.

    Review, not GLP-1 (industry-funded)

Sources

  1. 1. Grosicki GJ, Dhurandhar NV, Unick JL, et al. Sculpting Success: The Importance of Diet and Physical Activity to Support Skeletal Muscle Health during Weight Loss with New Generation Anti-Obesity Medications. Current Developments in Nutrition. 2024;8(11):104486. doi:10.1016/j.cdnut.2024.104486
  2. 2. Leidy HJ, Clifton PM, Astrup A, et al. The role of protein in weight loss and maintenance. The American Journal of Clinical Nutrition. 2015;101(6):1320S-1329S. doi:10.3945/ajcn.114.084038
  3. 3. Mozaffarian D, Agarwal M, Aggarwal M, 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. The American Journal of Clinical Nutrition. 2025;122(1):344-367. doi:10.1016/j.ajcnut.2025.04.023
  4. 4. Volek JS, Kackley ML, Buga A. Nutritional Considerations During Major Weight Loss Therapy: Focus on Optimal Protein and a Low-Carbohydrate Dietary Pattern. Curr Nutr Rep. 2024;13(3):422-443. doi:10.1007/s13668-024-00548-6
  5. 5. Charidemou E, Ashmore T, Li X, et al. A randomized 3-way crossover study indicates that high-protein feeding induces de novo lipogenesis in healthy humans. JCI Insight. 2019;4(12). doi:10.1172/jci.insight.124819