Adaptive thermogenesis is the body's tendency to lower its energy expenditure by more than shrinking body size alone accounts for during weight loss — part of why loss slows over time.
Updated Jul 18, 2026
Adaptive thermogenesis is the drop in energy expenditure that happens during weight loss over and above what the loss of body mass alone would predict. A smaller body naturally burns fewer calories, but during a sustained calorie deficit the body also turns down its resting burn a little further — an energy-conserving response to defend its reserves. The effect is usually modest, but it's real, and it's one reason weight loss slows the longer you stay in a deficit.
On a GLP-1, this matters because appetite suppression makes a deficit easy to sustain, so the "calories out" side quietly falls to meet the reduced "calories in" — contributing to a stall. Protecting muscle with adequate protein and resistance training helps defend resting metabolism against this drift. For the fuller picture, see calories in, calories out and what a calorie deficit is.
Leucine — An essential amino acid that is the main dietary trigger of muscle protein synthesis.
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