GLP-1 medication or the gym? Why it's not either/or

More and more people are asking us the same question: 'Should I go on a GLP-1 medication, or should I join a gym?' It's an understandable question, but it sets up a false choice. GLP-1 medications - semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro) and others - can be genuinely helpful tools, prescribed for weight management, type 2 diabetes and other health reasons. Strength training and good nutrition aren't the alternative to them. They're what make the results healthier and more likely to last.

A quick note before we start: we're coaches, not your prescriber. Decisions about starting, stopping or dosing medication belong with your GP or consultant. What we can talk about is what the research says about training and eating well alongside it.

What happens to muscle when weight comes off

Whenever you lose a significant amount of weight - by any method - not all of it is fat. Some comes from lean mass, which includes muscle (as well as water, organs and other tissue). This isn't unique to GLP-1s; it happens with diets and surgery too. But because these medications can produce large losses relatively quickly, the amount of lean mass lost can be significant.

In the STEP 1 trial of semaglutide (Wilding et al., New England Journal of Medicine, 2021), participants lost around 15% of their bodyweight, and body-scan data from a subgroup showed that roughly 40% of the weight lost was lean mass. Tirzepatide trials (SURMOUNT-1, Jastreboff et al., NEJM 2022) showed a somewhat lower share, around a quarter. Researchers are still debating how much of that is true muscle and how much it matters long term - but losing muscle is the opposite of what anyone wants, especially as we age.

Why strength training becomes non-negotiable

Muscle isn't just about how you look. It's what lets you carry the shopping, climb the stairs, get up off the floor and stay independent later in life. It's also metabolically active tissue that helps your body manage blood sugar. Strength training is already one of the most important things you can do for your health (we wrote about why strength matters after 50). On a GLP-1, it becomes essential.

Resistance training is the strongest signal you can give your body to hold on to muscle while you're in an energy deficit - a finding consistent across weight-loss research for decades, and now recommended specifically alongside GLP-1 therapy in a 2025 joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society (Mozaffarian et al., American Journal of Clinical Nutrition). Combining the two also seems to help results last: in a Danish trial (Lundgren et al., NEJM 2021), people who combined a GLP-1 medication with regular exercise kept off more weight and lost more body fat than those using either alone. And we know weight tends to come back when the medication stops - in the STEP 1 extension, participants regained around two-thirds of the lost weight within a year of stopping (Wilding et al., 2022). The muscle, strength and habits you build in the gym are what you keep.

The prescription doesn't need to be complicated: two to three full-body strength sessions a week, built around squats, hinges, pushes, pulls and carries, progressed gradually with good coaching. That's exactly what our small group PT is built around.

Less food means every bite counts

GLP-1 medications reduce appetite - that's a big part of how they work. But eating less means you have less food to work with, and it gets harder to get everything your body needs. The same 2025 advisory flags protein, fibre, and micronutrients such as iron, calcium, vitamin D and vitamin B12 as areas to watch, along with staying well hydrated.

In practice that means making your meals count. Prioritise protein at every meal - the advisory suggests roughly 1.2 to 1.6 g per kg of bodyweight per day, and if you're training, the upper end of that range is a sensible target. Include fruit, vegetables, legumes and wholegrains for fibre (which also helps with the constipation some people experience). Eat a variety of foods rather than leaning on the few that feel easy. Your GP may also suggest checking bloods or adding a supplement.

Don't let your intake drop too low

There's a flip side. When your appetite is very low, it's easy to drift into eating far too little - skipping meals, picking at food, getting through the day on coffee. Eating too little makes muscle loss worse, leaves you tired and flat in your training, and makes it harder to get the nutrients you need. The goal isn't to eat as little as possible. It's to eat enough, regularly, with meals built around protein and nourishing foods - even if they're smaller than they used to be. If you're struggling to eat enough or feeling unwell, talk to your prescriber.

This is the kind of practical, no-fuss support our nutrition coaching offers: not a strict plan, but helping you make the food you do eat work harder for you.

Both, together

So it's not GLP-1 versus the gym. For many people, the medication can help with appetite and weight. Alongside that, strength training protects your muscle, your strength and your long-term health. Good nutrition makes sure your body has what it needs while you eat less. Together, they give you the best chance of results you'll actually keep.

If you're on a GLP-1 medication, or thinking about it, and want to make sure you're doing it in a way that protects your strength, book a free consultation and we'll have a chat about where to start.