GLP-1 muscle loss: how to protect muscle while you lose weight

Some of the weight you lose on a GLP-1 is fat, and some is lean mass, which includes muscle. You have real ways to look after your muscle, starting this week.

How much of the weight lost is muscle?

In one major trial, 38% of the weight lost was lean mass, and roughly 20% was muscle.

A 2025 joint advisory from four nutrition and obesity medicine groups (ACLM, ASN, OMA and TOS) reports body scans from the STEP 1 trial of semaglutide. Of an average 13.6 kg lost:

Lean mass also includes water, organs and other tissue. The advisory estimates roughly 20% of total weight lost is muscle. Without structured strength training, that tends to be about 10 to 15% in women and 20 to 25% in men.

Why does muscle matter?

It keeps you strong, steady on your feet and able to do what you enjoy.

It helps you climb stairs, carry groceries and keep your balance as you age. The advisory notes bone can also be affected by larger and faster weight loss.

What helps most?

Enough protein and regular strength training, which work best together.

1. Eat enough protein

The advisory suggests 1.2 to 1.6 grams of protein per kilogram of body weight per day during weight loss, using an adjusted body weight for people with a higher body weight. A flat 80 to 120 grams a day is a simpler option. If you’re strength training, the range is 1.2 to 1.7 g/kg. The protein calculator works out your number.

Have protein at every meal, as the 2025–2030 Dietary Guidelines for Americans recommend, and eat it first. Shakes, bars or fortified foods can back you up on low-appetite days.

More in how much protein you need on a GLP-1.

2. Build in strength training

The advisory suggests strength training at least 3 times a week, plus at least 150 minutes of moderate aerobic activity, like brisk walking. The Physical Activity Guidelines for Americans recommend muscle-strengthening activity at least 2 days a week for adults in general.

That can mean your body weight, bands, dumbbells, gym machines, or tasks like carrying groceries and gardening.

How do I start strength training?

Start small: two or three short sessions a week, even 10 to 15 minutes each.

A simple at-home routine

Do each move 8 to 12 times, rest, then repeat once or twice:

1. Chair squats. Sit down and stand up from a sturdy chair, slowly.
2. Wall push-ups. Hands on the wall, lean in, push back.
3. Step-ups. Step onto the bottom stair and back down.
4. Band rows. Pull a band toward you, squeezing your shoulder blades.
5. Glute bridges. Lie on your back, knees bent, and lift your hips.

As these get easier, add a set, add a little weight or slow down.

What does a realistic week look like?

Three short strength sessions, a few walks, and protein at every meal.

• Monday, Wednesday, Friday: 20 minutes of strength training at home
• Tuesday, Thursday: a 30-minute walk
• Weekend: a longer walk, a bike ride or time in the garden

How do I know it’s working?

Look beyond the scale: everyday tasks start to feel easier.

You can do more repetitions than last month, stairs leave you less winded, and your clothes fit differently.

What if nutrition is falling short?

Muscle weakness, unusual tiredness or hair loss are signs to raise with your doctor.

A registered dietitian can help too. Pick one thing this week: protein at breakfast, or one short strength session. Imi plans meals like this for you each week, with protein built into every day. For the bigger picture, see eating well on a GLP-1.