Post-semaglutide weight regain in females with obesity: Associations with gut microbiota, bile acid metabolism, and central nervous system.

AIMS: To investigate the metabolic mechanisms underlying weight regain (WR) after semaglutide withdrawal in females with obesity, focusing on gut microbiota, bile acid metabolism, and central nervous system regulation. MATERIALS AND METHODS: In a prospective, single-arm interventional study, 28 women with obesity finished 36-week semaglutide treatment (2.4 mg/week) followed by 12-week withdrawal. Parallel animal studies used HFD-fed female rats with 4-week semaglutide intervention and 4-week withdrawal. Measurements included body weight, metabolic parameters, gut microbiota composition, bile acid profiles, and hypothalamic gene expression. RESULTS: During treatment, patients achieved significant weight loss (-16.9 ± 4.8 kg), but 71.4% exhibited WR (+5.1 ± 1.6 kg) post-withdrawal, with 78.5% reporting appetite rebound (≥30% increase in VAS score and a sustained ≥300 kcal/day rise). Animal studies showed post-withdrawal gut microbiota dysbiosis (increased Firmicutes/Bacteroidota ratio, reduced Clostridium sensu stricto 1), decreased ursodeoxycholic acid levels, and downregulated hypothalamic TGR5 expression. Hypothalamic orexigenic signaling (AgRP/NPY) rebounded while anorexigenic pathways (POMC/MC4R) attenuated. Improvements in hepatic and adipose lipid metabolism partially persisted through maintained AMPK/SIRT1 activation and AKT/mTOR suppression. CONCLUSIONS: The recurrence of WR and increased appetite after semaglutide withdrawal coincided with reversals in gut microbiota and related metabolic profiles. This pattern of changes may implicate gut-derived signals in the reactivation of central appetite pathways, providing a basis for investigating strategies to sustain weight loss.