Every conversation about muscle on these drugs eventually arrives at a percentage, and the percentage is almost always quoted without the thing that makes it interpretable. This analysis supplies both: what share of lost weight was lean tissue on each drug, and what happened when people lifted weights. The cost of that second part is the subject of the cost nobody prices, which this page does not repeat.
What was pooled
A 2026 systematic review included twenty randomized controlled trials covering 15,782 participants [1]. Heterogeneity was moderate at an I² of 68%, and Egger's test found no evidence of publication bias (p=0.23), which is a cleaner statistical picture than most pooled analyses in this field manage — cleaner, for instance, than the pooled estimates in bone, the outcome nobody prices.
The proportions
Lean mass accounted for 25% to 39% of the total weight lost with incretin agonists. Semaglutide was highest at 35.2% (95% CI 31.5 to 38.9), liraglutide 26.8% (23.1 to 30.5) and tirzepatide lowest at 25.4% (22.8 to 28.0).
Lifestyle intervention alone produced a comparable proportion at 26.2% (24.1 to 28.3), and the comparison against the drugs was not statistically significant (p=0.42). Adding resistance training to lifestyle gave 17.5% (14.2 to 20.8) — the most favorable profile in the analysis and the only one that differed meaningfully from the rest.
The cheapest line on the chart
The intervention that moved the number is the one nobody bills for. Lifting weights took the lean-mass share from roughly a quarter or a third down to under a fifth, across the same pooled literature, without altering what anyone paid for medication.
Set against that, the median billed rate for injected semaglutide across the 432 figures recorded here is $179 a month, read September 2026, or $2,148 a year. No seller on this roster charges for the thing that changed the outcome, and none of them mentions it either — a silence of a different kind from the ones counted in what nobody says about a higher dose.
What it does not settle
Whether any of this translates into weaker people. Lean mass on a scan is not strength, and the review measures tissue rather than function. What it establishes is that the tissue goes, that it goes at a similar rate whether the weight came off through a drug or through diet, and that one cheap intervention nearly halves it. Whether the whole purchase is worth making is the question in is a GLP-1 worth what it costs.