Eating well on Wegovy or Ozempic: protein, meals and fluids

What the medicine does

Wegovy and Ozempic contain semaglutide, and Mounjaro contains tirzepatide. They mimic a hormone that makes you feel full. In trials, people lost 5 to 18% more of their body weight than on placebo¹. In the large STEP 1 trial, people on semaglutide lost an average of 14.9% over 68 weeks, against 2.4% on placebo².

For many, that's a big step. But when you eat far less, there's also less room for what your body needs. That's why four American professional bodies have joined forces on guidance for how to eat on GLP-1 medicines¹.

Protein to protect your muscle

When you lose weight, you don't only lose fat. In STEP 1, body composition was measured in a subgroup: of the weight lost, 62% was fat and 38% was fat free mass, which includes muscle, organs and water¹. With tirzepatide it was roughly a quarter fat free mass and three quarters fat³.

The guidance notes that 1.2 to 1.6 g of protein per kilo a day has been proposed during active weight loss¹. It also points to strength training, or strength and cardio combined, as well established for keeping muscle¹. Read more in our guide to protein and weight loss.

• Start your meal with the protein, so it goes in before you're full.
• If you feel queasy, pick soft, gentle protein: yoghurt, skyr, cottage cheese, eggs, fish.
• Do strength exercises twice a week, if your doctor is happy with that.

Small meals and nausea

Stomach trouble is the most common side effect. In trials, 25 to 44% of people had nausea, 19 to 30% diarrhoea, 8 to 24% vomiting and 17 to 24% constipation¹. These tend to show up in the first weeks and when the dose goes up, and usually ease over time¹.

Some people get caught in a loop where nausea stops them eating, and going hungry makes the nausea worse¹. The guidance suggests a small breakfast followed by small meals every three to four hours, with enough to drink¹. Ginger or peppermint tea helps some people too¹. The NHS advises against alcohol, as it can make nausea and vomiting worse⁶.

Drink enough

Nausea, vomiting and diarrhoea can leave you dehydrated. The patient leaflet stresses that it's important to drink enough to prevent this, especially if you have kidney problems⁵. In the worst cases, severe dehydration can damage the kidneys¹.

• Keep a bottle of water with you and sip through the day.
• If you can't keep fluids down, contact your doctor.

Why logging still helps

When you're barely hungry, it's easy to think there's no need to keep an eye on your food. But the problem flips. The risk now is getting too little protein and too few nutrients. The guidance recommends keeping track of what you eat and drink, for example with food logs or food photos¹.

There's another reason too. When people in STEP 1 stopped the medicine, they regained two thirds of their weight loss within a year⁴. The habits you build while you're on the medicine are the ones you'll still have if you ever stop.