Health
Eating well on GLP-1 medicines
Semaglutide and tirzepatide shrink appetite, so every meal has to work harder. General principles for protein, muscle and small portions, to discuss with your prescriber.
Why food still matters
GLP-1 medicines such as semaglutide (Wegovy, Ozempic) and tirzepatide (Mounjaro) reduce appetite, and people taking them have been observed to eat 16–39% fewer calories. That is how they lead to weight loss, but it leaves fewer chances to get enough protein, fibre, vitamins and minerals. The NHS says you need a healthy, balanced diet alongside them.
A 2025 joint advisory from four US nutrition and obesity societies warns that low intakes, below about 1,200 kcal a day for women and 1,800 for men, make shortfalls of nutrients such as iron, calcium and vitamin D more likely. If you are struggling to eat enough, tell your prescriber.
Protein and muscle
Weight lost quickly is never all fat. In the main semaglutide trial about 38% of the weight lost was lean tissue, roughly half of which is muscle. The advisory notes this is similar to other treatments that produce large weight loss, and a separate review found the proportion varies widely between studies.
The advisory treats protein as a priority and cites proposed targets of 1.2–1.6 g per kg of body weight a day, or a simpler 80–120 g a day, while noting there is no consensus on the best figure. It pairs this with structured resistance training, which is well established for preserving lean mass during weight loss.
Eating with a small appetite
Eat the protein part of the meal first, in case you are full before the end. The advisory suggests low-volume, protein-rich foods such as fish, eggs, Greek yoghurt and cottage cheese, and notes that soups, smoothies and cottage cheese are often more appealing than heavier foods.
Nausea is the most common side effect, especially when starting or increasing the dose. Small meals every three to four hours, avoiding large or high-fat meals and drinking enough fluid can help. For constipation, the advisory suggests fluids and a gradual increase in fibre from food.
Worth knowing
- This guide covers general eating principles for adults. It does not replace advice from your prescriber or a dietitian, and food is not a substitute for the medicine. Never change your dose or stop treatment without speaking to them.
- If you take insulin or other diabetes or blood pressure medicines, speak to your clinician before changing how you eat.
- Persistent vomiting, severe stomach pain, or being unable to eat or drink enough needs prompt medical advice.
Common questions
How much protein should I eat on semaglutide or tirzepatide?
There is no agreed figure. The 2025 advisory cites 1.2–1.6 g per kg a day, or 80–120 g, as proposed targets. Ask your prescriber or dietitian what suits you, particularly if you have kidney disease.
Do I need to exercise as well?
If you can, yes. Resistance training is the best-supported way to hold on to muscle while losing weight, and the advisory recommends it alongside enough protein.
Can I drink alcohol?
The NHS says it is best to avoid alcohol while using these medicines, because it can make nausea and vomiting worse.
Sources
- Mozaffarian et al. (2025): Nutritional priorities to support GLP-1 therapy for obesity, joint advisory of four US lifestyle medicine, nutrition and obesity societies, Am J Clin Nutr
- Neeland et al. (2024): Changes in lean body mass with GLP-1-based therapies and mitigation strategies, Diabetes Obes Metab
- NHS: Semaglutide
- NHS: Tirzepatide
General information, not medical or dietary advice. Speak to a doctor or registered dietitian about your own situation.
