Body Composition, Food Intake, and Energy Expenditure in a Murine Model of Roux-en-Y Gastric Bypass Surgery.

BACKGROUND: The mechanisms by which Roux-en-Y gastric bypass surgery (RYGB) so effectively lowers body weight and improves glycemic control are not well understood, and murine models are essential for identifying the crucial signaling pathways involved. The aim of this study is to characterize the time course of RYGB on body weight, body composition, food intake, and energy expenditure in diet-induced obese mice and establish a tissue bank for global "omics" or targeted biochemical and structural analyses. METHODS: High-fat diet-induced obese mice were subjected to RYGB using an improved surgical technique with a small gastric pouch. The effects on body weight, body composition, food intake, and energy expenditure were compared to sham surgery, high-fat diet-restricted weight-matched controls, and never-obese chow-fed controls. RESULTS: Without mortality or complications, RYGB surgery in high-fat diet-induced obese mice gradually decreased body weight to a plateau that was more or less sustained for up to 12 weeks (33 g, -18 %, p < 0.01) and significantly lower compared with sham-operated mice (51 g, +25 %, p < 0.01), but higher (+18 %, p < 0.01) than age-matched, chow-fed control mice (27 g). Energy intake after RYGB was significantly suppressed compared to sham only for the first 10 days, but significantly higher compared to weight-matched mice. Energy expenditure after RYGB was higher throughout the study compared with weight-matched, but not sham animals. CONCLUSIONS: RYGB surgery in diet-induced obese mice results in similar body weight and body composition changes as observed in humans, but in contrast with humans, this is achieved mainly through increased energy expenditure rather than decreased food intake.