One of the first things many people notice when they start a GLP-1 medication, such as semaglutide or tirzepatide, is that they feel less hungry. Plates get smaller, some snacks disappear and, sometimes, a whole meal gets pushed back. Eating less is part of how the treatment works, but it has a quiet side effect: along with the calories, the day’s protein drops too.

In this article, you’ll see why that deserves attention and find practical ideas to keep your protein up even when your appetite is low.

What happens to lean mass

When weight goes down, not all of it is fat. Part of the loss comes from what’s called lean mass, which includes muscle. This happens with any weight loss, with or without medication.

The large trials that led to the approval of semaglutide (STEP 1) and tirzepatide (SURMOUNT-1) for the treatment of obesity measured body composition in some of the participants. In both, most of the weight lost was fat, but a meaningful share was lean mass.

Muscle isn’t just about looks. It supports the strength you need for everyday tasks, your balance, the energy you burn and your metabolic health over the years. That’s why a joint advisory published in 2025 by four American nutrition and obesity societies listed two measures that go together among the priorities of GLP-1 treatment: adequate protein and strength training.

How much protein?

There’s no single number that works for everyone. The right amount depends on your weight, your age, your exercise routine and, above all, your health. People with kidney disease, for example, may need a different target.

As a reference, a 2018 meta-analysis of people doing strength training found that gains in muscle mass stopped increasing at around 1.6 g of protein per kilogram of body weight per day (about 0.7 g per pound). That’s a research finding, not a prescription. The right target for you should be set with your doctor or dietitian.

What holds for almost everyone on treatment: when appetite drops, protein tends to fall below what the person used to eat. Knowing how much you’re getting today is already a good first step.

Spread it through the day

Instead of packing your protein into one big meal, which gets hard when you feel full quickly, it helps to spread it across the day. A 2018 review on the subject suggests that distributing protein over several meals helps the body use it to maintain and build muscle.

In practice, that can mean including a protein source at breakfast, lunch, snack time and dinner, even in smaller portions.

Practical ideas when your appetite is low

Start your meal with the protein. If you can only eat half the plate, make it the half with the chicken, fish, eggs or beans.
Keep easy options on hand. Hard-boiled eggs, plain yogurt, cheese, canned tuna and shredded chicken make a snack in minutes.
Lean on classic pairings. Rice and beans already add some protein, and a serving of meat, chicken, fish or eggs completes the plate.
Think light textures. On queasy days, cold or soft foods, like yogurt, ricotta and omelets, often go down more easily.
Talk about supplements before using them. Protein powder can help in some situations, but it’s worth checking with whoever follows your treatment.
Don’t forget water. Staying hydrated also helps with some gastrointestinal effects that are common early in treatment.

Strength training is part of the equation

Protein alone doesn’t preserve muscle: it needs a stimulus. Strength exercises, such as weight training, resistance bands or bodyweight exercises, are the signal that tells your body to hold on to lean mass. Start at your own pace and, if possible, with professional guidance.

Tracking helps you see the pattern

Many people are surprised when they log what they eat for a few days: low-appetite days usually have much less protein than it seems. Writing down your meals, on paper or in an app, helps you notice these patterns and bring concrete information to your appointment. In Rekomp, the Protein tab shows your daily total against a goal you can adjust.

Most importantly, remember that GLP-1 treatment is followed by health professionals. Bring your questions about food to your appointment: they’re part of your care.

Sources

Mozaffarian D, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory. American Journal of Clinical Nutrition, 2025.
Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). New England Journal of Medicine, 2021.
Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). New England Journal of Medicine, 2022.
Morton RW, 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. British Journal of Sports Medicine, 2018.
Schoenfeld BJ, Aragon AA. How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition, 2018.

Protein on GLP-1 treatment: why it matters and how to get enough