In the biggest trial of semaglutide, people lost about 15 percent of their body weight in 16 months.1 Tirzepatide went further, about 21 percent at the highest dose.2 Before these medicines, only surgery gave results like this.
The same trial also checked what the lost weight was made of. Close to 40 percent of it was lean tissue, mostly muscle, not fat.1
The medicine cuts down how much you eat. It cannot choose what you eat. That choice stays with you, and it decides whether you lose fat or lose your muscle along with it.
On this page
How these medicines work
GLP-1 is a hormone made in your gut. Your body releases it after a meal. It tells your brain you are full, and it slows down your stomach.
These medicines are man-made copies of that hormone. They are much stronger, and they stay in the body much longer. Semaglutide is sold in India as Rybelsus tablets and Wegovy injections. Tirzepatide is sold as Mounjaro.
On these medicines, hunger falls sharply. Small portions fill you. Most people stop snacking without trying.
People on semaglutide could eat as much as they wanted at test meals. They ate about a quarter less than the placebo group, without any diet instructions.3
These are prescription medicines. A doctor must first check if they are safe for you. Certain thyroid tumors in your family, or a past attack of pancreatitis, rule them out. Your doctor sets the dose and keeps checking on you while you take them.
The muscle problem
When you eat very little, your body burns fat, but it also breaks down muscle. The faster you lose, and the less protein you eat, the more muscle you lose. That is how 40 percent of the loss in the trial came from lean tissue.1
Muscle burns calories even when you rest. Lose muscle, and your daily burn falls. That makes regain easier the day the medicine stops. Muscle also keeps you strong and helps control blood sugar. And after your 40s, muscle once lost is very hard to build back.
Two things protect muscle while you lose weight: protein, and strength exercise. On these medicines, both need planning, because hunger will no longer remind you to eat.
Protein first, at every meal
Aim for 1.2 to 1.6 g of protein per kg of body weight per day.4 For a 75 kg person, that is 90 to 120 g of protein.
That was easy to eat before the medicine. Now your stomach fills after a few bites. So the protein has to come first.
At every meal, eat the protein part before the roti or rice. Eggs, paneer, curd, chicken, fish, soy chunks. Dal is good but weak on its own. One katori gives only 6 to 8 g of protein, so add curd or paneer to the same meal.
Spread the protein across the day. Three meals with protein work better than one big protein meal, because the body cannot use a large amount at once.
If food alone cannot reach the target, whey protein in water or milk is a fair option. Plain unflavored whey works just as well as the costly brands.
The rest of the plate
Constipation is one of the biggest complaints on these medicines. Food moves slowly, and many people almost stop eating plants. Vegetables, fruit, whole dals, oats, flax seeds, or isabgol keep the gut moving. Drink 2 to 3 liters of water a day.
Eating very little also cuts your vitamins and minerals. Iron, B12, and calcium fall short easily, more so for vegetarians. Unusual tiredness or hair fall are warning signs. Tell your doctor about them instead of ignoring them.
Go easy on oily and deep-fried food. Your stomach now empties slowly, so oily food sits in it for hours. It is the most common trigger of nausea and reflux. Eat small meals, eat slowly, and stop at the first feeling of fullness. Be extra careful in the week after a dose increase. That is when a heavy or very sweet meal hits hardest.
Strength training, 2 to 3 times a week
The body keeps muscle that is used. Muscle that sits unused gets broken down first. So protein alone cannot save it.
In studies of people on low-calorie diets, strength training prevented most of the muscle loss.5 You do not need a gym. Squats, wall pushups, resistance bands, or light dumbbells at home are enough. Do 2 to 3 short sessions a week. Walking is good, but it does not protect muscle the way lifting does.
We coach clients on GLP-1 medicines: meal plans that reach the protein target inside a small appetite, side effect management, and habits that last after the course.
Book a consultation on WhatsAppPreparing for the day the medicine stops
In the year after stopping semaglutide, trial participants regained about two-thirds of the weight they had lost.6
The medicine works only while it is in your body. When you stop, hunger returns.
The months on the medicine are the easiest months to change how you eat, because hunger stays quiet while you practice. Make protein-first meals, home food, daily walks, and two strength sessions your normal week. That routine stays with you after the prescription ends.
If you only eat small portions of your old diet, nothing really changes. After stopping, the old diet comes back, in full portions.
Common mistakes
The worst mistake is hardly eating at all because hunger is gone. It speeds up muscle and hair loss and leaves you weak. Skipping protein because you are "hardly eating anyway" makes it worse. Pushing for a higher dose to lose faster adds side effects and does not improve the end result.
Buying these medicines without a prescription skips the safety checks a doctor must do first. And stopping suddenly, with no plan agreed with your doctor, usually ends in regaining the weight within a year.
The bottom line
These medicines cut how much you eat, and in trials close to 40 percent of the lost weight was lean tissue when diet was ignored. Eat 1.2 to 1.6 g of protein per kg every day, protein first at each meal. Add fiber and 2 to 3 liters of water for the constipation. Keep meals small and light to avoid nausea. Do strength exercise 2 to 3 times a week. Build the eating routine you plan to keep after the medicine, and stay under your doctor's care throughout.
Common questions
How much protein should I eat on a GLP-1 medicine?
Aim for 1.2 to 1.6 g per kg of body weight per day, split across your meals. Eat the protein part of each meal first. Use eggs, paneer, curd, chicken, fish, or soy, and add whey protein if food alone is not enough.
Why am I losing muscle or hair on Mounjaro or Wegovy?
Fast weight loss with very little food starves the body of protein and nutrients. Muscle breaks down along with fat, and hair fall is a common response. Both improve with more protein, enough total food, and strength exercise. Tell your doctor and dietitian instead of pushing through.
Will I regain the weight after stopping?
Without new habits, most of it comes back. In the year after stopping semaglutide, trial participants regained about two-thirds of the lost weight. The habits you build during treatment are what stay with you after it.
References
- Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002.↑︎
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205-216.↑︎
- Blundell J, Finlayson G, Axelsen M, et al. Effects of once-weekly semaglutide on appetite, energy intake, control of eating, food preference and body weight in subjects with obesity. Diabetes Obes Metab. 2017;19(9):1242-1251.↑︎
- Leidy HJ, Clifton PM, Astrup A, et al. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015;101(6):1320S-1329S.↑︎
- Sardeli AV, Komatsu TR, Mori MA, Gaspari AF, Chacon-Mikahil MPT. Resistance training prevents muscle loss induced by caloric restriction in obese elderly individuals: a systematic review and meta-analysis. Nutrients. 2018;10(4):423.↑︎
- Wilding JPH, Batterham RL, Davies M, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. Diabetes Obes Metab. 2022;24(8):1553-1564.↑︎
This article is educational and complements, never replaces, advice from your treating doctor.