Sleeve gastrectomy protects lean mice from future obesity.

Background: Obesity and metabolic disease drive premature aging and reduced lifespan. While metabolic interventions like calorie restriction, protein restriction, and time restricted feeding have been shown to improved lifespan, they are either not effective or sustainable for most humans. Bariatric surgery is the most efficacious metabolic intervention available and is associated with increased lifespan. However, whether its longevity benefits derive solely from weight reduction or reflect surgery-specific metabolic reprogramming remains unknown. Methods: We employed a lean mouse model of sleeve gastrectomy (SG) in which young, lean male C57BL/6J mice underwent SG or sham operation while maintained on low-fat chow, then were challenged with high-fat diet (HFD) in midlife. We assessed glucose metabolism, body composition, energy expenditure, hepatic histology, adipose tissue inflammation, and cecal microbiome composition. Results: Despite identical weight and food intake on low-fat chow, SG mice demonstrated improved glucose tolerance and insulin sensitivity prior to HFD challenge. Upon HFD exposure, SG animals exhibited enhanced metabolic flexibility with greater capacity for fat oxidation, increased energy expenditure, attenuated weight gain, and reduced adiposity compared to sham controls. SG further reduced hepatic lipid accumulation and attenuated visceral adipose tissue inflammation, marked by decreased pro-inflammatory cytokine expression and reduced macrophage infiltration. These metabolic benefits occurred independently of caloric intake. Cecal microbiome profiling revealed surgery-specific remodeling characterized by Lactobacillus enrichment and reductions in Verrucomicrobia and Clostridia - a pattern distinct from caloric restriction and consistent with prior SG studies. Conclusions: Early-life SG confers durable, weight-loss-independent protection against midlife metabolic deterioration. Gut microbiome remodeling, particularly enrichment of Lactobacillus species, represents a candidate mediating mechanism and a potential therapeutic target for aging and metabolic disease.