Tirzepatide vs. semaglutide: how they compare for weight loss
How tirzepatide and semaglutide work, what head-to-head research shows, side effects, cost and how to choose with your clinician.
When you lose weight, you lose a mix of fat and lean mass. That's true for diets, surgery and medication. In body-composition substudies of the major GLP-1 trials, lean mass made up roughly a quarter to two-fifths of the total weight lost. The good news: you have real influence over that ratio.
Why muscle matters
Muscle keeps you strong, steady on your feet and metabolically healthy, and it makes it easier to keep weight off. It matters even more as we age.
1. Lift something, twice a week
Resistance training is the strongest signal you can send your body to keep muscle. It doesn't have to be a gym: bodyweight squats, push-ups against a counter, resistance bands or carrying groceries all count. Aim for two or three sessions a week that work your legs, back, chest and arms.
2. Protein at every meal
With a smaller appetite, protein is easy to under-eat. Put it first on the plate and aim for a palm-sized portion at each meal. See our guide to eating on a GLP-1 for practical ideas.
3. Sleep and steady pace
Muscle repairs while you sleep, and very fast weight loss makes lean-mass loss more likely. Seven to nine hours, and a dose schedule your clinician adjusts to how you're feeling, both help.
Sources
- Wilding JPH et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med. 2021;384:989-1002.
- Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med. 2022;387:205-216.
- Mozaffarian D et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory. Am J Clin Nutr / Obesity / ACLM. 2025.
This article is for general information and isn’t medical advice. See our Important Safety Information.
