November 12, 2026

Losing weight on a GLP-1? Protect your muscle

By Jarah Breese Exercise Scientist, Longevity Consultant & founder of Elements For Life

If you're taking a GLP-1 medication such as semaglutide or tirzepatide,(Ozempic) the number on the scale is probably heading the way you wanted. The question I care about as an exercise scientist is what that weight is made of. Fat is the target. Muscle isn't.

This article looks at what the clinical trials show about muscle during GLP-1 weight loss, what major nutrition bodies recommend, and where protein and creatine fit in the evidence, including the places where the evidence runs out.

 

What people on GLP-1s are actually doing

Recent European market data from Lumina Intelligence, reported by NutraIngredients in October, shows the typical GLP-1 user isn't who most people assume. Many are health-conscious people who already exercise and take supplements, and who are struggling with the last stubborn weight.

Nearly 60% of surveyed users said they had increased their supplement use since starting. Protein was the most common choice (50.6%), followed by vitamin D, multivitamins and fibre. Creatine came in at 31.65% and HMB at 14.57%.

The side effects people reported help explain those choices:

  • Nausea (26.83%)

  • Constipation (25.41%)

  • Mood changes (22.02%)

  • Fatigue or low energy (21.69%)

     

Only 12.16% reported losing muscle or strength. That is a self-reported figure, and in my experience muscle loss is easy to miss until it has progressed, so I'd treat it as a floor rather than a ceiling.

 

What the trials show about lean mass

The two landmark trials both ran body-composition scans on a subset of participants.

In the semaglutide STEP 1 substudy (140 people, 68 weeks), body weight fell 15%. Fat mass dropped 19.3% and lean mass dropped 9.7%. Because fat fell faster, lean mass actually rose as a share of total body weight, by about 3 percentage points.

In the tirzepatide SURMOUNT-1 substudy (160 people, 72 weeks), body weight fell 21.3%, fat mass 33.9% and lean mass 10.9%. Roughly 75% of the weight lost was fat and 25% was lean mass, a split similar to the placebo group. An age breakdown showed no excess lean loss in older groups, although only 20 people in that analysis were 65 or over.

There are two honest ways to read this. The encouraging reading is that most of what's lost is fat, and body composition generally improves. The cautious reading is that a quarter of the loss being lean mass still means roughly one kilogram of lean tissue for every three kilograms of fat. Wider reviews put the range higher, with some finding that 15% to 40% of weight lost can be fat-free mass.

 

Why it matters more after 50

Muscle mass and strength already decline with age. Add rapid weight loss and the risk of sarcopenia, the age-related loss of muscle and function, goes up. Reviews consistently flag older adults, postmenopausal women and people with low starting muscle as the groups most at risk.

The drivers are mostly practical rather than a toxic effect of the drug: eating less (including less protein), moving less, and a blunted response of muscle to protein as we age. That is good news, because those are things we can influence.

There is also the period after treatment. Lumina's data, drawing on Cambridge research, notes that people who stop typically regain 60% to 75% of the weight they lost within the first year. Among people who had stopped, 34.6% said they had increased their protein intake to help manage this.

 

Protein: the first lever

A 2025 joint advisory from four major bodies (the American College of Lifestyle Medicine, American Society for Nutrition, Obesity Medicine Association and The Obesity Society) lists adequate protein and strength training to preserve lean mass among its eight nutritional priorities for people on GLP-1s.

The figure most often suggested during weight loss is 1.2 to 1.6 grams of protein per kilogram of body weight per day, well above the 0.8 g/kg baseline. For a 75 kg person that works out to roughly 90 to 120 grams a day. It's worth knowing that this target comes from weight-loss and healthy-ageing research more broadly, not from a trial specific to GLP-1 users. People with kidney disease should speak to their doctor before raising protein, and a dietitian can tailor the number to an individual.

The difficulty is that appetite suppression, nausea and early fullness make that amount of food hard to eat. GLP-1 drugs also slow gastric emptying. When a meal feels like a chore, a protein drink is often the easier way to close the gap, and spreading protein across the day tends to work better than trying to fit it into one or two meals.

 

What about whey protein hydrolysate?

Whey is a fast-digesting, leucine-rich protein, and leucine is the amino acid that most strongly switches on muscle protein synthesis. Hydrolysed whey takes that a step further: the protein is pre-broken into smaller peptides, so your body has less digesting to do before the amino acids are available to your muscles.

That matters on a GLP-1. When nausea, constipation and early fullness are already part of the picture, a heavy protein that leaves you bloated and uncomfortable is the one people stop taking. Many people find hydrolysed whey noticeably easier on the stomach, which makes it far easier to keep up every day.

It also does its job once it's down. Research reviewed in the sports nutrition literature found hydrolysed whey produced a larger rise in blood amino acids and muscle protein synthesis than soy or casein. When you're eating less overall, you want every serve to count, and a protein that is gentle, quick to absorb and easy to stay consistent with is a real practical advantage.

 

Look at what else is in the scoop

Protein per scoop isn't standardised, and it varies more than most people realise. A conference analysis of commercially available protein powders found protein ranged from 15% to 90% of a 35 g serve, with the lowest-protein products often relying on fillers such as maltodextrin. The same analysis found artificial sweeteners in 46.1% of products, thickeners and stabilisers in 47.1%, and emulsifiers in 25%.

Independent testing points the same way. ConsumerLab reported quality problems in five of the 16 protein products it tested, and a supplement-testing body cites studies in which 11 of 41 UK products and 15 of 61 US products contained less protein than their label claimed. A scoop is only a volume, so a big serve on the label can still deliver only 20 to 22 g of protein once the non-protein material is accounted for.

That is why we're upfront about the numbers. One scoop of Muscle Formula delivers 34 g of protein. In a scoop of the same size, many other powders deliver around 22 g or less, with the rest of the scoop made up of fillers and other ingredients that do nothing for your muscles.

On a GLP-1, where every serve is hard-won, that gap matters twice. You need fewer serves to reach your target, and there is less in the shake to upset an already sensitive stomach. Some people find that thickeners, gums and sweeteners make bloating worse, so it's worth reading the ingredient list.


Training is what makes protein work

Protein supplies the material. Resistance training provides the signal to use it. Reviews consistently describe resistance training with adequate protein as the best-established strategy for protecting muscle during weight loss. A 2025 review notes that the evidence in GLP-1 patients specifically is still mixed, and the trials are still catching up. But as an exercise scientist, my professional opinion is clear: weight training is essential for anyone on a GLP-1.

The physiology of preserving muscle in a calorie deficit doesn't change because the deficit comes from a medication, and nothing else gives your body the same signal to hold on to muscle. Put together, a GLP-1, a high-protein diet and consistent weight training is, in my view, the gold standard for results: more fat lost, more muscle kept, and a body far better placed to hold those changes for the long term.

The medication handles the appetite. Protein and training build the body you actually want to keep.

 

Creatine: a smaller, supporting role

Creatine is among the most studied supplements in sport, and the older-adult evidence is solid. A meta-analysis of 22 randomised trials (721 participants, average ages from 57 to 70) found that adding creatine to resistance training produced about 1.4 kg more lean tissue than training alone, along with greater chest-press and leg-press strength. An earlier meta-analysis found gains in fat-free mass and better chair-stand performance, with no change in fat mass.

The important phrase there is during resistance training. Creatine helps you train a little harder, and the training is what drives the result.

Creatine fits what a GLP-1 user needs. The muscle loss seen on these medications is driven largely by eating less, moving less and a blunted response to protein. Creatine combined with resistance training works on exactly those problems: in older adults it consistently adds lean mass and strength beyond training alone, and it helps you train harder when energy is low.

The pieces line up from several directions. Fatigue is reported by more than one in five GLP-1 users, and nearly a third say they take or are considering creatine. A 2026 review looked specifically at creatine's role in limiting muscle wasting and strength decline during GLP-1 therapy. And the direct research is now under way, with a registered pilot trial randomising 40 people starting a GLP-1 to 10 g of creatine a day or placebo alongside 12 weeks of resistance training.

Put that together with the strong older-adult evidence and a long safety record, and creatine is a smart, well-supported addition to a muscle-first plan on a GLP-1.

It makes sense that interest is high, given that more than one in five users reports fatigue. Two practical notes: creatine draws water into muscle, so the scale can creep up slightly early on, which is not fat gain; and staying well hydrated is sensible if you're also dealing with GI side effects. Anyone with kidney problems should check with their doctor first.

 

Putting it together

In order of importance:

  1. Strength train two to three times a week. This is the signal your body needs to hold on to muscle.

  2. Hit a protein target. Around 1.2 to 1.6 g/kg is the commonly suggested range, spread across the day, using a protein drink where appetite makes food difficult.

  3. Don't under eat. Very low intake makes both protein and training harder, so talk to your prescriber if appetite is suppressing food intake more than you expected.

  4. Consider creatine as an add-on if you're training, with realistic expectations.

  5. Track strength and function, not just the scale. If your lifts and daily movement are holding up, that is a better sign than any single scan number.

     

Where Elements For Life fits

Muscle Formula and Creatine are the two products we make for the protein and creatine pieces of this picture. . They're tools that assist you with you longevity and exercise so you can get the most out of your GLP-1 and any longevity based lifestyle program.

 

Want a plan built around your body, your history and your goals? Book a Health & Longevity consult with me and get a clear, evidence-based path to feeling stronger and more energetic. Enquire Here

 

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This article is general information, not medical advice. If you're taking a GLP-1 medication or have a medical condition, talk to your doctor or an accredited dietitian before changing your diet or adding supplements.

 

 

 

Written by Jarah Breese