Mechanism of Gastric Bypass-Induced Body Weight Loss: One-Year Follow-up After Micro-Gastric Bypass in Rats

Bariatric surgery (Roux-en-Y or mini-gastric bypass) is designed to limit food intake by creating a small gastric pouch and to reduce nutrient absorption by bypassing the long limb of the intestine. We report 1-year follow-up results after micro-gastric bypass in rats. Micro-gastric bypass was performed by anastomosis of the esophagus and the proximal jejunum. Body weight, body composition, bone mineral density, food intake, and serum levels of ghrelin and obestatin were measured. Growing rats had a 40% weight reduction 2 months after micro-gastric bypass surgery compared to 20% after gastrectomy and 30% after stomach bypass (anastomosis of the esophagus and duodenal bulb). Six months after micro-gastric bypass surgery, the rats stopped growing compared to controls that gained continuously due to expansion of the fat compartment. Adult rats (600 g) lost 30% of their body weight 5 months after the micro-gastric bypass, while food intake was not reduced. Serum levels of obestatin (but not ghrelin) were reduced in rats with micro-gastric bypass. The results suggest that micro-gastric bypass efficiently reduced body weight, particularly fat mass; loss of the weight after micro-gastric bypass was not due to reduced food intake; and lean tissue and bone development were impaired in growing subjects after gastric bypass.