Strength · In the news
Strength Training on Weight-Loss Jabs: How to Protect Your Muscle
Muscle loss on Mounjaro and Wegovy is a hot topic in the UK, so here is what the evidence actually says and a simple two-day strength plan to help you keep the muscle you have.
TL;DR
- On a weight-loss jab, strength training on two days a week, plus enough protein and food overall, is the simplest way to help protect your muscle.
- A review commissioned by Les Mills and backed by ukactive says 20 to 50% of the weight lost on these medicines can be lean mass rather than fat.
- Trial data is calmer: in one major tirzepatide (Mounjaro) study, about three quarters of the weight lost was fat.
- Start lighter than you think, build up slowly, and plan sessions around days when side effects are quieter.
- Always follow your prescriber's or GP's advice. Edge does not give medical or prescribing advice.
2 days
of muscle-strengthening work a week, the NHS guideline for all adults
74%
of weight lost was fat in a 72-week body-scan study of tirzepatide (Mounjaro)
20 to 50%
of weight lost can be lean mass, says a review backed by ukactive
Weight-loss jabs such as Mounjaro (tirzepatide) and Wegovy (semaglutide) can lead to losing some muscle as well as fat, and exactly how much is now one of the biggest talking points in UK health and fitness. You do not need to settle the debate to act on it: regular strength training, plus enough protein and food overall, is the simplest way to help protect your muscle while your weight comes down.
Much of the UK coverage traces back to a review commissioned by fitness company Les Mills and backed by the not-for-profit ukactive, which called for strength training support for everyone taking these medicines. It was back in the spotlight in late September 2026, when researchers at a European diabetes conference in Milan presented trial results for an experimental medicine designed to reduce muscle loss on semaglutide. Here is what is known, what is not, and a simple plan to start once your prescriber or GP is happy for you to train.
What is the news about weight-loss jabs and muscle loss?
The review was led by Dr Gillian Hatfield of the University of the Fraser Valley in Canada and pulled together existing research on these medicines. Its headline claim is that 20 to 50% of the weight people lose on them can be lean mass rather than fat. The authors compared the scale of that loss to what is seen after bariatric surgery or roughly ten years of ageing, and flagged that losing muscle and bone could leave middle-aged and older adults more at risk of frailty and falls.
Its main recommendation is simple: strength training two to three times a week, alongside 150 minutes of moderate to vigorous activity. Importantly, the authors also said there is not yet specific research on the best strength routine for people on these medicines, and that more work is needed.
It is fair to note that the report comes from the fitness sector, which has an interest in more people training. Its advice lines up with mainstream UK guidance, but the numbers are worth reading alongside the trial data below.
Do you actually lose muscle on Mounjaro or Wegovy?
Some, yes, but most of the weight lost in the big trials has been fat. In a body-composition substudy of SURMOUNT-1, a major tirzepatide trial, 160 adults had body scans at the start and after 72 weeks. Published in Diabetes, Obesity and Metabolism in 2025, it found that people taking tirzepatide lost about 21% of their body weight on average, and roughly 74% of what they lost was fat and about 26% was lean mass. The placebo group, who had diet and activity advice but lost far less weight, showed a similar split.
A few things help put this in context:
- Lean mass is not the same as muscle. It covers everything that is not fat, including muscle, water and organs, so not every kilo of lean mass lost is muscle.
- Some lean mass loss is normal. The placebo group lost some too, without the medicine.
- The two camps are closer than the headlines suggest. A quarter of weight lost as lean mass sits inside the review's 20 to 50% range. A 2026 analysis of 36 studies, reported in the International Journal of Obesity, also described lean mass loss as present but relatively small compared with total weight loss.
- Both sides agree on what to do. The British Heart Foundation says these injections can lead to some loss of muscle as well as fat, and that regular exercise and resistance training can help you maintain muscle as you lose weight.
NICE recommends a reduced-calorie diet and more physical activity alongside these medicines, and strength training fits neatly into that.
Why does keeping muscle matter while you lose weight?
Muscle lets you climb stairs, carry the shopping and stay steady on your feet. Keeping it means more of the change you see is fat, and you finish the process feeling stronger, not just lighter.
A strength habit can also stay with you for life, long after any course of treatment. Our guide on how to lose fat without losing muscle covers the principles in more detail.
How should you start strength training on a weight-loss jab?
Gently, and with a green light from your prescriber or GP, especially if you are new to exercise, managing a health condition or have recently changed dose. A few ground rules:
- Start lighter than you think. Finish every set feeling you could do three or four more reps.
- Plan around side effects. The NHS lists feeling or being sick, constipation and diarrhoea among the common side effects of tirzepatide. Train on the days you feel more like yourself.
- Do not train on empty. Training on almost nothing can feel rough, so many people find a small snack and some water beforehand helps.
- Stop if something feels wrong. If you feel dizzy, faint, unusually breathless or have chest pain, stop and get medical advice.
If lifting is completely new to you, our beginner guide on how to start strength training walks you through the basics, from form to choosing weights.
What does a simple two-day strength plan look like?
This plan works the major muscle groups the NHS mentions (legs, hips, back, abdomen, chest, shoulders and arms) in two sessions of about 30 to 40 minutes, for example Monday and Thursday. You can do it at home with a couple of dumbbells and a resistance band, or in a gym.
| Slot | Day A | Day B | Sets and reps | Easier option |
|---|---|---|---|---|
| Legs | Sit-to-stand from a chair | Step-ups onto a low step | 2 to 3 sets of 8 to 12 | Higher chair, or hold a rail |
| Push | Incline press-up on a counter | Seated dumbbell shoulder press | 2 to 3 sets of 8 to 12 | Wall press-up, or lighter weights |
| Pull | One-arm dumbbell row, hand on a chair | Resistance band row or lat pulldown | 2 to 3 sets of 10 to 12 | Lighter weight or band |
| Hips | Glute bridge | Dumbbell Romanian deadlift | 2 to 3 sets of 10 to 12 | Bodyweight only |
| Core and grip | Farmer's carry (walk holding weights) | Dead bug | 2 to 3 rounds of 20 to 30 seconds | Lighter weights, smaller movements |
Rest for about a minute between sets. Then build up slowly over the first two months:
| Weeks | Sets per exercise | How it should feel | Focus |
|---|---|---|---|
| 1 to 2 | 1 to 2 | Easy, with 3 or 4 reps left in the tank | Learn the moves and find your starting weights |
| 3 to 4 | 2 | Steady, with 2 or 3 reps left | Same weights, smoother form |
| 5 to 8 | 2 to 3 | Challenging, with about 2 reps left | Add a little weight once you hit the top of the rep range with good form |
Consistency beats intensity. Two steady sessions a week for months will do far more than one heroic session that leaves you sore and put off.
How much protein and food do you need on a weight-loss jab?
These medicines work by reducing your appetite, which makes it easy to eat far less protein and food overall than your body needs to recover from training. The British Heart Foundation advises making sure your diet still has enough protein, vitamins and minerals, and suggests small, regular meals with enough lean protein, calcium and vitamin D. In practice that might look like:
- A protein source at every meal, such as eggs, Greek yoghurt, fish, chicken, beans, lentils or tofu.
- Eating the protein part of your plate first if you tend to fill up quickly.
- Smaller, more regular meals rather than one big meal you struggle to finish.
- Plenty of fruit, vegetables and wholegrains alongside, so you get the fibre and nutrients you need.
Exact amounts vary, so ask your prescriber, GP or a registered dietitian what is right for you. For background, our guide on how much protein you need to build muscle explains how protein supports training, but personal advice from your care team comes first while you are on medication.
Should you do cardio too, or just weights?
Both have a place. The NHS recommends at least 150 minutes of moderate activity a week, or 75 minutes of vigorous activity, on top of strength work on two days. Brisk walking is a brilliant start. Later you might add gentle running intervals, cycling or HIIT, but there is no rush. Strength sessions are the part most people skip, and the part that matters most for keeping muscle.
What does the research not tell us yet?
- There is no agreed best strength routine for people on these medicines yet, which the review's own authors point out.
- Most studies measure lean mass on a scan, which is not the same as measuring strength or how well people manage day to day.
- Experimental medicines aimed at protecting muscle are still being tested, and whether protecting muscle this way leads to long-term gains in strength and function is not yet known. They are not something you can start now.
- People respond differently depending on age, starting fitness, dose and how much weight they lose.
How can Edge help you train alongside your treatment?
Edge builds one fully personalised plan across strength, running, HIIT and mobility, ready within 24 hours, and you can message a real coach anytime. If energy is low one week, ask your coach about shorter sessions. 20,000+ members train with Edge. Edge is free to download, and Edge Pro comes with a 7-day free trial (a card is needed to start).
One important line: Edge does not give medical or prescribing advice. Questions about your medicine, your dose or side effects always go to your prescriber or GP, and their advice comes first.
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This article is general guidance, not medical advice. If you are new to exercise, returning from injury, or managing a health condition, speak to your GP before starting, and see a physio for any niggle that does not settle.
