Abstract
OBJECTIVES: The potential benefits of combining lifestyle changes with weight loss pharmacotherapies for obesity treatment are underexplored. Building on recent clinical observations, this study aimed to determine whether "lead-in" calorie restriction before administering clinically approved weight loss medications enhances the maximum achievable weight loss in preclinical models. METHODS: Diet-induced obese mice (DIO) were exposed to 7 or 14 days of calorie restriction before initiating treatment with semaglutide (a glucagon-like peptide-1 receptor (GLP-1R) agonist), tirzepatide (a GLP-1R/glucose insulinotropic peptide receptor (GIPR) co-agonist), or setmelanotide (a melanocortin-4 receptor (MC4R) agonist). Follow-up assessments using indirect calorimetry determined the contributions of energy intake and expenditure linked to consecutive exposure to dieting followed by pharmacotherapy. RESULTS: Calorie restriction prior to treatment with semaglutide or tirzepatide enhanced the weight loss magnitude of both incretin-based therapies in DIO mice, reflected by a reduction in fat mass and linked to reduced energy intake and a less pronounced adaptive drop in energy expenditure. These benefits were not observed with the MC4R agonist, setmelanotide. CONCLUSIONS: Our findings provide compelling evidence that calorie restriction prior to incretin-based therapy enhances the achievable extent of weight loss, as reflected in a weight loss plateau at a lower level compared to that of treatment without prior calorie reduction. This work suggests that more intensive lifestyle interventions should be considered prior to pharmacological treatment, encouraging further exploration and discussion of the current standard of care.