Exercise and GLP-1: training to help preserve muscle mass

Do you lose muscle when taking a GLP-1 medicine?

Yes, some. When you lose weight, not everything the scales show is fat. You also lose lean mass, which includes muscle, water and other tissues. In a sub-study of tirzepatide (Mounjaro), around a quarter of the weight lost was lean mass and three quarters was fat [2].

The proportion was similar in the group that lost weight without the medicine [2]. According to a joint recommendation from four US scientific societies for nutrition and obesity, protein alone is probably not enough to preserve muscle without strength training [1]. That is why we work on both at the same time in consultations.

The risk of losing muscle is higher with age, during perimenopause and menopause, with a very sedentary lifestyle, or when a low appetite means you are not getting enough protein [1]. If any of these situations sound familiar, it is worth making strength training a regular part of your week.

Find out how much protein you need and how to spread it through the day when your appetite is low in protein and muscle with a GLP-1. For an explanation of how semaglutide, tirzepatide and other medicines work, see the guide to GLP-1 medicines. Here, we focus on training.

This matters beyond the duration of treatment. When it is time to maintain your weight, preserving muscle can help you keep moving with ease. If you are concerned about what happens when you stop taking the medicine, find out more in how to manage weight regain after Ozempic or Wegovy.

Low on energy? What should you train first?

When you are eating less, you have limited energy for exercise, so it makes sense to choose carefully. Ideally, combine strength training at least two days a week, and preferably three, with aerobic activity such as walking or cycling [1] [3]. If you can only manage one, make it strength training, because aerobic activity alone offers less protection for your muscles as you lose weight [1].

You do not need a gym. Squats from a chair, press-ups against a wall or worktop, step-ups or pulling on a resistance band all count as strength training because your muscles work against resistance [3]. The WHO recommends working all the major muscle groups over the course of the week [3].

The strength you maintain matters as much as the weight you lose.

A qualified exercise professional should decide how to put this together, including the number of sets and repetitions and how much to increase the load. We have not provided a set programme because it depends on your starting point, your age and how you respond.

If you feel nauseous or tired that day

“Should I train as usual if I feel unwell today?” This is one of the questions we hear most often in consultations, and the answer is no. Reducing the intensity that day means adapting to what your body can manage. A shorter or gentler session helps you maintain the habit better than pushing yourself and then not wanting to exercise again for several days.

If you only feel up to a short walk, that counts too. If nausea or tiredness continues for several days in a row, or stops you moving normally, mention it to the person who prescribes your medicine. Reviewing your treatment plan is their decision.

Do you need to eat more to exercise?

Not necessarily more overall. What often helps is making sure each meal includes some protein and starting your meal with it, so you get enough even when your appetite is low [1]. Forcing yourself to eat larger portions to improve your performance can make you feel nauseous; it is better to organise what you already eat.

Hydration matters more than usual. Nausea, vomiting or diarrhoea, which the medicine can sometimes cause, may leave you with less fluid than you realise, so it is important to avoid dehydration [1]. Drink water before, during and after exercise, especially in hot weather.

If you have diabetes and take other medicines

If you have type 2 diabetes and use insulin or a sulphonylurea as well as a GLP-1 medicine, check with your healthcare team before changing your exercise routine [1]. They can advise you on when to check your blood glucose and whether your medication needs adjusting.

If you have never done strength training

Strength training can work just as well for someone who has not exercised for years. Any activity that makes a muscle work against resistance counts, from carrying the shopping to climbing stairs with a load or doing the simple exercises above [3].

The aim in the first few weeks is consistency. Try to move even on the days when you feel least like it, and remember that starting small is better than not starting.

You will not notice a change straight away either. You are more likely to notice improvements in everyday strength, such as climbing stairs or carrying the shopping, before you see a difference on the scales or in the mirror.

What mistakes do we see in consultations?

• Waiting until you have more energy to start. When your appetite is low, that day may take a while to come, and a short session on a better day still counts.
• Stopping exercise once you reach your target weight. This is when muscle can help most with maintaining what you have achieved.
• Using exercise to make up for what you have eaten. If exercise starts to feel like punishment or leaves you feeling guilty, talk about it; at Alimmenta, our Psychology team can help.
• Comparing your pace with someone else’s. What matters is making progress from your own starting point.

And the question that often comes at the end of a consultation has a short answer. Exercise does not replace your medication, and your doctor continues to decide the dose.