Losing more than weight? Watch out for muscle and bone loss

Anna-Louise Dearden | Last update: 4th July 2025

TL;DR 

• Up to 40% of weight lost on GLP-1s may be muscle, not just fat
• Muscle matters for metabolism, energy, blood sugar – and independence
• Rapid weight loss may also impact bone density, especially long-term
• Protein + resistance training = your armour against unwanted loss
• You don’t always need to hit the gym: bands, bodyweight or a few dumbbells at home can work wonders

Muscle: more than just looking good

It turns out that when you’re using GLP-1s and seeing rapid weight loss, 25–40% of that drop can come from muscle.

“Muscle is vital not just for our lifespan – but our healthspan,” says Dr Mosley.

He goes on to say “It keeps us mobile and independent. It burns calories and acts like a glucose sponge – soaking up blood sugar.

But that doesn’t mean it’s inevitable. “Muscle loss can be avoided – or substantially minimised,” says Dr Mosley, who is also author of the book Food Noise: How weight loss medications & smart nutrition can silence your cravings.

His go-to plan?

– Eat plenty of protein at each meal

– Include resistance training two or three times a week

– Start with simple home-based bodyweight exercises or resistance bands

Search 7-minute workouts online or using beginner-friendly platforms like The Fast 800.

Research done by Professor Naveed Sattar, from Glasgow University’s School of Cardiovascular and Metabolic Health, shows weight loss drugs don’t result in faster muscle loss and “…will help reassure many that muscle loss is not necessarily meaningfully greater with these drugs than from weight loss from other methods.”

Protein isn’t optional now

Nutritionist and therapist, Harry Snell agrees. He takes the protein point even further.

“When someone’s appetite is already suppressed from these medications, I want to make sure every bite is working as hard as possible,” he says. That means aiming for 1.2–1.6g of protein per kg of bodyweight – and spreading it out over the day.

“Quality animal proteins like chicken, beef, fish, eggs, or dairy are the most efficient. They contain leucine, which triggers muscle building, plus all the essential amino acids your body needs to recover and maintain.”

Not sure how that looks on your plate? Try:

• A 3-egg omelette with ham
• A 120g serving of salmon or chicken
• 200g of low-fat Greek yogurt

If you’re vegan?

• 160g cooked edamame
• 330g cooked lentils

But what about bones?

“Most GLP-1 studies have only run for 6–24 months,” Harry explains. “Bone health wasn’t really what they were measuring. That said, there are some early signs that rapid weight loss could negatively affect bone density, especially if it’s not supported by the right exercise and nutrition.”

Harry also advises to be mindful around falls, which are the leading cause of injury-related death in the over-65s in the UK. A sobering fact – and something we should all care about, no matter our age. Harry includes a whole section on his site for falls risk advice.

“Ultimately, bones need a reason to stay strong,” says Harry. “The resistance training I recommend for muscle? It helps bones too. So does protein, which is more important than calcium.”

Can you get stronger on a jab?

Absolutely. Harry says many of his clients have used their weight loss medication as a kick-start into building better habits – not just losing fat.

“Think of it like this,” he says. “Your appetite is lower. That’s a perfect time to build structure – not just eat less.”

That structure might include:

• Setting protein targets
• Meal prepping small but nutrient-dense portions
• Walking daily
• Trying simple strength routines at home

It’s not rocket science, and it’s all things we already know; but having even small targets helps.

The SlimrChat takeaway

We know weight loss jabs can be powerful. But they aren’t magic, and they don’t work in isolation. And if you’re not moving your body and fuelling it right, the weight you lose might be the kind you really need to keep.

Here’s your SlimrChat starter plan:

Protein with purpose: Hit 1.2–1.6g per kg of your body weight, spread through meals. Think chicken, fish, eggs, dairy, or high-quality plant combos. Here’s some easy protein snack recommendations from our team.

Resistance is essential: Two to three strength sessions a week – bodyweight, bands, dumbbells, whatever you can stick with.

Don’t wait to feel weak: Start muscle and bone support from week one on a jab. Prevention > regret.

Every bite counts: When your appetite drops, make every meal muscle-smart.

Want to stay strong while getting lighter? Start now.

More resources:

• British Heart Foundation – Protein
• Fast 800 Exercise Plans
• NHS Strength and Flex Exercise Plan
• Royal Osteoporosis Society – preventing falls
• Harry Snell’s Muscle + Bone Health Tips
• NHS Wegovy Overview

Want to know what it looks like in real life?

Join the SlimrChat community. Our members share what actually works — the food, the habits, the hard days and the wins. You’ll find real talk, honest support and tips to help you make the most of your meds. No shame. No fluff. Just real people getting real results. Click the button below and join the chat!