GLP-1 Muscle Loss: How to Keep Your Muscle

The jeans are loose. The scales are finally behaving. People keep telling you how well you look.

So why did carrying the shopping up one flight of stairs feel like a serious workout?

And why does wrestling the lid off a jar make you feel like your arms and hands have lost all their power?

·       Christine, one of my clients, is on a GLP-1 prescribed by her doctor. She told me she could not go to her pump class anymore because of her sheer exhaustion. “Just getting to the gym makes me tired.”

If this is you, stop blaming yourself. You have done nothing wrong. You were handed a powerful medication and about ninety seconds of advice on what to do with your fork while you are on it.

So let me say the thing nobody said at the pharmacy counter, doctor’s office, or telehealth call.

We need to talk about your muscle.

How much muscle do you lose on a GLP-1?

Your scales are a terrible gossip. They tell you how much you lost. They have no idea what you lost.

When weight comes off fast, by any method, part of it is fat and part of it is lean mass. That is everything in your body that isn't fat, and muscle is a big slice of it.

How big a slice? Researchers who reviewed the GLP-1 trials found lean mass made up anywhere from about 15 per cent to as much as 40 to 60 per cent of the weight people lost, depending on the study.

Read that again. In some studies, close to half.

A caveat, because I want you informed and calm. Lean mass on a scan is more than muscle. It includes water and organ tissue too. And some loss is normal, because a lighter body needs a little less muscle to carry it around.

The trouble starts when you lose more than you need to. On a tiny appetite, with no plan, that is very easy to do.

Why muscle matters when you are losing weight

Muscle does far more than fill out a T-shirt.

It is where a big share of your blood sugar goes after a meal. It keeps your metabolism ticking over. It holds your bones steady and gets you up off the floor.

Think of it as your super. You barely notice it at 45. You will be very glad it's there at 75.

Now add this. Many people will come off these medications at some point. If you arrive at that day with less muscle than you started with, you are trying to hold your new weight with a smaller engine. What a way to set yourself up, huh?

It's science, baby. And you have a big say in how it goes.

I think of it in three moves. Feed it. Lift it. Rest it.

Feed it: how much protein you need on a GLP-1

When your appetite shrinks, protein is usually the first thing off the plate. It's filling. It takes chewing. Tea and toast is so much easier.  It’s easy to slip into a carb trap.

I get it. But your muscle is listening to every meal, and tea and toast tells it nothing.

The clinical guidance for people losing weight on these medications sits at roughly 1.2 to 1.6 grams of protein per kilo of body weight a day. For most of us that works out at 25 to 30 grams each meal.

In real food, that looks like:

·       A palm-sized piece of chicken or salmon

·       Two eggs with a generous scoop of Greek yoghurt on the side

·       A cup of cottage cheese with berries and a handful of nuts

·       A big serve of tofu, or lentils with an egg on top

My best tip costs nothing. Eat the protein first. Your stomach has limited room right now, so give the front of the queue to the food doing the heavy lifting.

On the days when nothing sounds good, drink it. A smoothie with yoghurt and a scoop of protein powder. A cup of broth with shredded chicken stirred through. A quality whey or pea protein shake is fine as well.

This is nourish not punish, remember. Consistent beats perfect. Read that line again…consistency beats perfection!

One flag. If you have kidney disease or any other medical condition, check your protein target with your doctor first.

Lift it: strength training on a GLP-1

Eating less tells your body to let go. Lifting something heavy tells it what to hang on to.

That is the whole job of resistance training on a GLP-1. It is a memo to your muscle that says, "Still needed. Do not remove."

Two to three sessions a week will do it. Leave a day between them.

You don't need a gym, a trainer or lycra. Squats. Push-ups against the kitchen bench. Rows with a resistance band. Carrying something heavy from A to B. Wear a weighted vest. Twenty minutes counts.

Then make it a touch harder over time. One more rep. A heavier dumbbell. The gym people call this progressive overload. I call it not letting your body get bored.

And if formal exercise feels like too much this week, go for micro habits. Ten squats while the kettle boils. You will feel ridiculous. Do it anyway.

Rest it: how sleep protects your muscle

Training is the request. Sleep is where the order gets filled.

One of my favourite studies put people on the same reduced-calorie diet, twice. Once with eight and a half hours in bed. Once with five and a half.

Same food. Same people. On short sleep they lost 55 per cent less fat and 60 per cent more lean tissue.

It was a small study, ten people over two weeks, but that result should make every tired but wired person sit up. You can eat beautifully and train faithfully, and a run of bad nights will still undo a good chunk of it.

So guard your seven to nine hours like a meeting with someone important. It is one.

Two smaller things. Drink your water, because when you eat less you often drink less too. And watch your energy as closely as your weight. If you are flat, foggy and dragging by mid-afternoon, that is your dashboard light telling you the tank needs more fuel.

Your three micro habits for this week

1.     Tomorrow's breakfast has protein in it, and you eat that part first.

2.     Two 20-minute strength sessions go in the diary, with a day between them.

3.     Lights out 30 minutes earlier, four nights out of seven.

That's it. Three small things.

You went on this medication to feel better in your body. Keep your muscle and you get to actually use that body. Haul the suitcase off the carousel. Carry the grandkids. Dance badly at weddings until the lights come on.

Quick questions

How much muscle do you lose on a GLP-1?

It varies. In trials, lean mass made up anywhere from about 15 per cent to as much as 40 to 60 per cent of the weight lost. Lean mass includes water and organ tissue too, so not all of it is muscle.

How much protein do I need on a GLP-1?

Guidance for people losing weight on these medications is roughly 1.2 to 1.6 grams of protein per kilo of body weight a day, spread across your meals. If you have kidney disease or another medical condition, check with your doctor first.

How do I keep muscle while losing weight on a GLP-1?

Eat enough protein, do strength training two to three times a week, and protect your sleep. Feed it. Lift it. Rest it.

Do you have any questions or comments… come on…ask away!

General information only. Please talk to your GP or prescriber about what is right for you.

References

1.     Neeland IJ, Linge J, Birkenfeld AL. Changes in lean body mass with glucagon-like peptide-1-based therapies and mitigation strategies. Diabetes, Obesity and Metabolism, 2024.

2.     Mozaffarian D, Agarwal M, Aggarwal M, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. The American Journal of Clinical Nutrition, 2025.

3.     Nedeltcheva AV, Kilkus JM, Imperial J, Schoeller DA, Penev PD. Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of Internal Medicine, 2010.