Protein on a GLP-1

GLP-1 muscle loss: how much protein helps protect muscle?

Part of the weight lost on a GLP-1 is lean mass: about 38% in the STEP 1 semaglutide trial, as summarised in a 2025 joint advisory. The advisory pairs adequate protein, with 1.2–1.6 g/kg a day proposed during active weight loss, with strength training at least three times a week.

Planning guidance, not medical advice · Updated 2026-10-20

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What the numbers say

The joint advisory (American College of Lifestyle Medicine, American Society for Nutrition, Obesity Medicine Association, The Obesity Society; 2025) reviews body composition on GLP-1 therapy. In the STEP 1 trial, of an average 13.6 kg weight reduction, 8.3 kg (62%) was fat and 5.3 kg (38%) was lean body mass. With muscle about half of lean mass, that is roughly a fifth of the weight lost. Modelling cited in the same advisory puts muscle at 10–15% of weight lost in women and 20–25% in men without structured strength training.

Protein and training, together

The advisory proposes protein of 1.2–1.6 g/kg a day during active weight reduction (or an absolute 80–120 g a day), says GLP-1 therapy should come with a structured exercise program, and recommends strength training at least three times weekly with at least 150 minutes of moderate aerobic activity. It also says protein alone is likely inadequate to preserve muscle.

Weight used	1.2–1.6 g/kg	At 1.4 g/kg
130 lb (59 kg)	71–94 g	83 g
150 lb (68 kg)	82–109 g	95 g
170 lb (77 kg)	93–123 g	108 g
200 lb (91 kg)	109–145 g	127 g
230 lb (104 kg)	125–167 g	146 g
260 lb (118 kg)	142–189 g	165 g
300 lb (136 kg)	163–218 g	191 g

Tracking it

Protein Only keeps one number in view, grams against a goal you can set with its GLP-1 mode from your current or goal weight. Mark shot days and appetite, and the monthly muscle-protection summary (Pro) shows days at goal and how shot-week days compare with the rest. It tracks protein; it does not measure muscle.

Guidance, not medical advice. Protein Only is a tracking tool and does not treat or manage any condition or medication. If you take a GLP-1 such as Ozempic, Wegovy, Zepbound or Mounjaro, ask your prescriber or dietitian what protein target suits you, especially if you have kidney disease or another health condition. Ozempic, Wegovy, Zepbound and Mounjaro are trademarks of their owners; Adelyons is not affiliated with them.

Sources

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. Obesity (Silver Spring). 2025;33(8):1475-1503 (published online 30 May 2025). DOI 10.1002/oby.24336. Read it. Quoted: Higher targets, such as 1.2–1.6 g/kg/day, have also been proposed during active weight reduction. Accessed 2026-10-20.
Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376-384. DOI 10.1136/bjsports-2017-097608. Read it. Quoted: Protein supplementation beyond total protein intakes of 1.62 g/kg/day resulted in no further gains in fat-free mass. Accessed 2026-10-20.
Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press; 2005. DOI 10.17226/10490. Read it. Quoted: Recommended Dietary Allowance for protein in adults: 0.8 g/kg/day. Accessed 2026-10-20.

Questions

How much muscle do people lose on a GLP-1?

In STEP 1, of an average 13.6 kg weight reduction, 8.3 kg (62%) was fat mass and 5.3 kg (38%) was lean body mass. Because muscle is about half of lean mass, the advisory estimates roughly 20% of the weight lost was muscle.

Is protein enough to keep muscle?

The advisory says increased protein intake alone is likely inadequate to preserve muscle mass, and recommends strength training at least three times a week plus at least 150 minutes of moderate aerobic activity.

How much protein a day protects muscle on a GLP-1?

Targets of 1.2–1.6 g per kg of body weight a day have been proposed during active weight reduction, above the 0.8 g/kg baseline. Ask your prescriber or dietitian for yours.

One dial, one number

Track it in Protein Only

Set this number as your goal, log in two taps, and turn on GLP-1 mode to mark shot days and appetite. Protein Only flags a run of short days after a shot, and the monthly muscle-protection summary (Pro) puts shot-week days next to the rest. No calorie counting, no account; your log stays on your phone.

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