Am I losing muscle?

Answer

Some of what comes off is lean tissue — body-composition substudies commonly report roughly a quarter to two fifths of total weight lost. Whether that is harmful is debated.

In more detail

Body-composition substudies of the STEP and SURMOUNT programs, and real-world cohorts, consistently report an estimated 25 to 40% of total weight lost as lean tissue. That proportion is broadly what happens in any rapid weight loss, pharmacological or not. A 2024 Circulation primer argued the muscle changes look adaptive rather than maladaptive — proportionate to the weight lost, with improved muscle quality and insulin sensitivity — while noting that older adults and people already close to frailty are the group where the concern is real. Both of those things are true at once, which is why the conversation is loud.

Source

Neeland et al., Diabetes Obes Metab 2024 (doi 10.1111/dom.15728); Circulation 2024 primer on muscle mass and GLP-1 receptor agonists.

Educational use only, never medical advice. No doses.