Nutrition on GLP-1 Medications
Eating to protect your muscle, feel better, and keep the results
GLP-1 medicines, such as semaglutide (Wegovy, Ozempic) and tirzepatide (Mounjaro), are prescription-only treatments for weight loss and type 2 diabetes. They mimic gut hormones, slowing how fast your stomach empties and reducing appetite, so you naturally eat less. They are started, dosed and monitored by your doctor or a specialist weight-management service. This guide is about the nutrition that goes alongside that medical care, to help you protect your muscle, feel well day to day, and hold on to the results. It is general education, not medical, prescribing or dosing advice.
What the evidence shows
| The research | What it means for you |
|---|---|
| Real weight loss | In the STEP 1 trial, semaglutide plus lifestyle change gave around 15% average weight loss over about 16 months. Newer medicines such as tirzepatide can be higher. |
| Muscle goes too | Roughly a quarter to 40% of the weight lost can be muscle and other lean tissue, not just fat, unless you actively protect it. |
| Weight often returns | After stopping, people regained about two-thirds of their lost weight within a year on average. Appetite comes back when the medicine stops, so your habits are what hold the line. |
Protect your muscle: the biggest win
- Prioritise protein at every meal. Aim for roughly 1.2 to 2.0 g per kg of body weight a day, spread across the day. With a smaller appetite, eat your protein first: eggs, fish, chicken, dairy, beans or tofu.
- Do resistance training 2 to 3 times a week. Lifting or bodyweight work, combined with enough protein, sharply reduces muscle loss without slowing fat loss.
- Muscle is not just about looks. It drives your metabolism, strength and mobility, and it is a big part of keeping the weight off later.
A worked example. An 80 kg person aiming for 1.8 g/kg needs about 145 g of protein a day, which is roughly 35 to 40 g at each of four meals or snacks. Not 80 kg? Work out your own target with our Calorie & Macro Estimator.
Grams can feel abstract, so here is what about 35 to 40 g of protein looks like on a plate (roughly one meal's worth):
| Food | For about 35 to 40 g of protein |
|---|---|
| Chicken breast | About 130 g cooked (a portion the size of your palm and a half) |
| Salmon | About 160 g cooked, one large fillet |
| Eggs | About 6 eggs |
| Cottage cheese | A large 300 g tub |
| Greek yoghurt | About 350 g of 0% fat |
| Lentils or beans | About 400 g cooked. Plant proteins are less concentrated, so go bigger or combine sources |
| Whey or soya shake | 1 to 2 scoops |
Mix and match to taste. A day might be an omelette and yoghurt at breakfast, chicken at lunch, salmon and lentils at dinner, and a shake or cottage cheese to top up, landing near 145 g.
Eat enough of the good stuff
- Your appetite may drop sharply, so what you do eat has to count. Build small meals around protein, then vegetables and fruit, then wholegrain carbohydrates.
- Do not fill a small appetite with sugary or ultra-processed foods. There is less room for error now, so nutrient-dense choices matter more.
- Fibre and fluids help prevent the constipation these medicines can cause. Aim for vegetables, fruit, wholegrains, and water through the day.
- Your prescriber or a dietitian may suggest a general multivitamin or a specific supplement if your intake is very low. Follow their advice rather than self-prescribing.
Managing side effects with food
- Nausea is the most common effect. Eat smaller amounts more often, choose blander, lower-fat foods, eat slowly, and stop when full.
- Go easy on greasy, very sweet or spicy foods, which tend to make nausea worse. Ginger or peppermint tea can help.
- For reflux, avoid lying down straight after eating. For constipation, lean on fibre, fluids and movement.
- Contact your GP or prescriber about persistent vomiting, severe or ongoing tummy pain, or any side effect that worries you.
Plan for life after the medicine
- The medicine controls appetite for you. When it stops, appetite returns, which is why on average about two-thirds of lost weight comes back within a year.
- Use your time on it to build the habits that keep weight off: a protein-rich balanced plate, regular meals, portion awareness, resistance training and an active routine.
- Agree any plan to reduce or stop the medicine with your medical team, and line up your nutrition and training support for that transition.
This leaflet is general nutritional guidance for education only. It is not medical advice, diagnosis or treatment, and it does not replace advice from your GP or a registered dietitian. Always check with a qualified professional before making significant changes, particularly if you have a health condition, are pregnant, or take medication.