GLP-1 medications like Wegovy, Ozempic and Mounjaro help your body eat less and burn fat. But the medication alone is not enough. What you eat and whether you exercise has a major impact on whether you lose fat — or fat and muscle. This article gives you practical advice that is easy to follow, whether you are a beginner or an experienced exerciser.

Why do you lose muscle during weight loss?

When the body loses weight quickly, it is not only fat that disappears. Studies show that 20–40% of the weight lost during GLP-1 treatment can come from muscle mass. That might sound like a small percentage, but muscles matter: they keep your metabolism up, give you strength in daily life, and help you maintain your weight in the long run.

The good news is that you can protect your muscles with two simple steps: eating enough protein and doing strength training. Research from Massachusetts General Hospital shows that patients who combine GLP-1 medication with regular resistance training and adequate protein intake can preserve the vast majority of their muscle mass.

How much protein do you need?

Protein is the most important nutrient when you are in weight-loss treatment. It keeps you full, requires energy to digest, and is the raw material your muscles are built from.

A good rule of thumb is to aim for 1.2–1.6 grams of protein per kilogram of body weight per day. If you weigh 80 kg (176 lb), that is 96–128 grams of protein daily. As a minimum, you should eat at least 60 grams of protein per day, even if you are eating very little overall.

Spread your protein intake across 3–4 meals and aim for 20–30 grams of protein per meal — this gives your body the best opportunity to build and maintain muscle continuously.

Good protein sources

What should you avoid?

GLP-1 medication slows the rate at which the stomach empties — food stays in the stomach longer than usual. This means that fatty and fried foods can worsen side effects such as nausea, reflux and stomach discomfort. Avoid or limit:

What should you eat more of?

Prioritise foods that are nutrient-dense and filling, without containing too many calories. While on GLP-1 treatment, most people automatically eat less, so it is especially important that what you eat is of high quality.

Calorie intake: how little is too little?

Many patients find that their appetite drops dramatically on GLP-1 medication. It is tempting to eat very little, but it is important not to go below 1,200 calories per day for women or 1,500 calories for men. Eating too little risks:

Talk to your doctor or a dietitian if you are unsure about what you should be eating.

Exercise: what works best?

You do not need to become an athlete. But regular movement — particularly strength training — makes a significant difference to whether you lose fat or muscle.

Strength training (2–4 times per week)

Strength training is the most effective form of exercise for preserving and building muscle mass. It does not have to take place in a gym — bodyweight exercises (squats, push-ups, lunges) are perfectly adequate, especially at the start. Key principles:

Cardiovascular exercise (2–3 times per week)

Walking, cycling, swimming and dancing are excellent for your heart and fitness. Cardio burns calories and improves blood sugar — but it does not replace strength training when it comes to muscle preservation. Combine both types for the best results.

Everyday movement counts too

You do not only need to train in sets and series. Taking the stairs instead of the lift, walking to the shops and standing up from your desk once an hour all contribute to your overall activity level. Research shows that daily general activity has significant health benefits regardless of organised exercise.

When will you feel the effects?

Many people find that the first 4–8 weeks are the hardest to maintain good habits, as appetite is already low and fatigue can be an issue. Start gently and gradually increase the intensity. Even 10–15 minutes of strength training 2–3 times a week is better than nothing.

After 2–3 months, most people notice that their energy levels rise, movement feels easier, and it becomes easier to maintain the routine. Remember: the medication helps you eat less — it is your diet and exercise that shape your body as you lose weight.

A typical day

Here is an example of how a day might look during GLP-1 treatment:

Summary

GLP-1 medication is a powerful tool, but it works best in combination with the right diet and regular exercise. The most important advice:

With these habits in place, you are well equipped to get the most out of your GLP-1 treatment — and to maintain the results in the long run.

Sources