Losing weight on a GLP-1? What the research says about keeping your muscle.

The medications work. The part nobody puts in the ad is what else comes off with the fat.

How much of the loss is muscle

A 2026 systematic review and meta-analysis of randomised trials found that lean mass made up 25 to 39 percent of the total weight lost on incretin medications: about 35 percent with semaglutide and about 25 percent with tirzepatide (PubMed). A narrative review puts the typical range at 20 to 30 percent (PubMed). In a real-world twelve-month cohort of seventy people, lean mass fell 1.75 percent while fat mass fell 5.9 percent, and the more weight people lost, the more lean mass went with it (PubMed).

Some lean-mass loss always comes with weight loss. The concern is losing more than you need to, at an age when it is slow to rebuild.

What the guidance says to do about it

A 2026 scoping review of older adults on GLP-1 medications lands on two things: a protein intake of 1.2 to 1.6 grams per kilogram of body weight per day, and resistance exercise tailored to the person (PubMed). In a network meta-analysis of 41 trials, adding exercise reduced the lean-mass loss seen with liraglutide (PubMed).

That is the honest answer: eat enough protein, and lift something a couple of times a week. Talk to your prescriber about both.

The practical problem

The protein target arrives at exactly the moment eating is hardest. Appetite is down, portions are small, and a thick shake is often the last thing that will go down. Half a slice of toast can be a win.

This is the gap Rejuvenate is built for. One stick in water is five calories and contains no protein. It is the essential amino acids protein has to be broken down into, with that step already done, and it activates muscle comparable to 20g of protein per serving†. It is light enough to drink when a shake is not an option.

It is not a replacement for the protein in your food, and it does not change what your prescriber tells you about your own situation. It is a way to hit the muscle signal on the days the meal did not happen.

See the 12-Week Supply →

Sources

1. Lean mass changes with incretin therapy versus lifestyle intervention: systematic review and meta-analysis of RCTs. PubMed
2. GLP-1 receptor agonists and lean mass: narrative review. PubMed
3. Real-world 12-month cohort, n=70. PubMed
4. Curr Nutr Rep 2026 scoping review: older adults on GLP-1 receptor agonists. PubMed
5. Diabetes Obes Metab 2026, network meta-analysis of 41 RCTs. PubMed
6. Bukhari SSI et al. Am J Physiol Endocrinol Metab 2015. PubMed

† These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Rejuvenate contains no protein.