Bariatric Surgery and the Gut Hormone Response

Obesity has become an epidemic in the United States and is reaching epidemic levels in many other countries. Although obesity itself can have deleterious effects, the attributed comor- bidities contribute greatly to the overall health decline of affected populations. Overweight and obese individuals are at increased risk for many diseases and health conditions. Medical, psychological, and endoscopic therapies for weight loss have been tried; however weight loss is usually only modest, with weight regain common. Bariatric surgery has been reported to be the most effective method for achieving major, long-term weight loss, with weight loss ranges of 35%-40% lasting as long as 15 years. Patients often lose weight at a rapid rate, with resolution or remission of many obesity-related comorbidities. Although the procedure itself plays a role in the weight loss after surgery, the resultant metabolic changes have been linked to alterations in the gut hormones. Although these changes have been the focus of much research, they are not completely understood. Two hypotheses have been proposed to explain this conflicting data. The hindgut hypothesis suggests that the quick transit of nutrients to the distal bowel improves glucose metabolism by stimulating secretion of glucagon-like peptide-1 and other appetite-suppressing gut peptides. The foregut hypothesis suggests that there is a yet unknown factor that promotes insulin resistance and type 2 diabetes mellitus. Further research is essential and could lead to less invasive therapies with fewer complications and side effects than bariatric surgery. © 2010 American Society for Parenteral and Enteral Nutrition.