Semaglutide-induced weight loss increased skeletal muscle mitochondrial efficiency in mice, producing more ATP per unit of oxygen — a metabolic adaptation that may contribute to weight regain after stopping treatment.
Increased ATP/O2 ratio in muscleSemaglutide-treated mice produced more energy per unit of oxygen consumed in skeletal muscle, indicating greater mitochondrial efficiency that could reduce overall calorie burning and promote weight regain.
What the researchers found
Semaglutide treatment led to significant reductions in both fat and lean mass in high-fat diet-fed mice. Skeletal muscle OXPHOS efficiency (ATP produced per O2 consumed) increased in permeabilized muscle fibers after semaglutide treatment. Mitochondrial proteomics revealed changes in only two proteins — LYRM7 and TTC19 — both linked to complex III assembly (p<0.05 without multiple testing corrections). No substantial changes in the abundance of OXPHOS subunits were observed, suggesting the efficiency gain comes from assembly optimization rather than increased mitochondrial content.
Why it matters
Weight regain after stopping GLP-1 agonists is one of the biggest clinical challenges in obesity medicine. Understanding the metabolic adaptations that promote regain is essential for developing strategies to maintain weight loss. This study identifies a specific mechanism — increased muscle mitochondrial efficiency — that reduces calorie burning during weight loss and may drive the body to regain weight when the drug's appetite-suppressing effects end.
How the study worked
C57BL/6J mice were fed a high-fat diet for 12 weeks to induce obesity, then received semaglutide or vehicle for 1 or 3 weeks. Skeletal muscle OXPHOS efficiency was measured using high-resolution respirometry and fluorometry in permeabilized muscle fibers, determining ATP production rates relative to oxygen consumption. Mitochondrial proteomics was performed to identify protein-level changes underlying the efficiency shift.
What this study cannot tell us
This is a mouse study, and metabolic responses to semaglutide may differ in humans. The treatment periods (1 and 3 weeks) are short relative to typical human treatment courses. The proteomic changes reached significance only without multiple testing corrections, meaning they could be false positives. The study did not directly demonstrate that the efficiency increase causes weight regain — this is a hypothesis. Fat and lean mass were both reduced, but the relative contributions weren't fully characterized.
How to read the evidence
This is a well-designed preclinical mechanistic study using high-resolution respirometry and proteomics. However, the short treatment duration, mouse model limitations, and marginal statistical significance of proteomic findings (p<0.05 without multiple corrections) temper the conclusions.
When this study was published
Published in 2025, this study addresses one of the most pressing clinical questions about GLP-1 agonist therapy — why weight comes back — using cutting-edge metabolic measurement techniques.
The bigger picture
The weight regain problem with GLP-1 agonists has implications for millions of patients and billions in healthcare spending. If muscles become more fuel-efficient during weight loss, the body essentially lowers its energy needs — creating a metabolic environment that favors regain. Understanding this at the molecular level (complex III assembly) could eventually lead to combination therapies that prevent this adaptation, allowing patients to maintain weight loss after stopping GLP-1 drugs.
Questions still open
- Does the same mitochondrial efficiency adaptation occur in humans taking semaglutide, and does it correlate with weight regain severity?
- Could targeting complex III assembly prevent the metabolic adaptation and help maintain weight loss after stopping GLP-1 agonists?
- Is the increased mitochondrial efficiency reversible, or does it persist even after weight is regained?
Common questions
Why do people regain weight after stopping semaglutide?
Does semaglutide change how muscles work?
Read the original research
Semaglutide-induced weight loss improves mitochondrial energy efficiency in skeletal muscle.
Obesity (Silver Spring, Md.), 33(5), 974-985
Citation
Choi, Ran Hee; Karasawa, Takuya; Meza, Cesar A; Maschek, J Alan; Manuel, Allison M; Nikolova, Linda S; Fisher-Wellman, Kelsey H; Cox, James E; Chaix, Amandine; Funai, Katsuhiko. (2025). Semaglutide-induced weight loss improves mitochondrial energy efficiency in skeletal muscle.. Obesity (Silver Spring, Md.), 33(5), 974-985. https://doi.org/10.1002/oby.24274