Roux-en-Y gastric bypass enhances energy expenditure and extends lifespan in diet-induced obese rats.

Gastrointestinal weight-loss surgery (GIWLS) is currently the most effective treatment for severe obesity, with Roux en-Y gastric bypass (RYGB) among the best of the available surgical options. Despite its widespread clinical use, the mechanisms by which RYGB induces its profound weight loss remain largely unknown. This procedure effects weight loss by altering the physiology of weight regulation and eating behavior rather than by simple mechanical restriction and/or malabsorption as previously thought. To study how RYGB affects the physiology of energy balance, we developed a rat model of this procedure. In this report, we demonstrate that RYGB in diet-induced obese (DIO) rats induces a 25% weight loss, prolongs mean survival by 45%, and normalizes glucose homeostasis and lipid metabolism. RYGB induced a 19% increase in total and a 31% increase in resting energy expenditure (REE). These effects, along with a 17% decrease in food intake and a 4% decrease in nutrient absorption account for the normalization of body weight after this procedure. These effects indicate that surgery acts by altering the physiology of weight regulation and help to explain the effectiveness of RYGB in comparison to restrictive dieting and other forms of dietary and pharmacological therapies for obesity. The clinical effectiveness of RYGB and its physiological effects on body weight regulation and energy expenditure (EE) suggest that this operation provides a unique opportunity to explore the mechanisms of energy homeostasis and to identify novel therapies for obesity and related metabolic diseases.