“Gastric pouch emptying of solid food in patients with successful and unsuccessful weight loss after Roux-en-Y gastric bypass surgery” by L.N. Deden et al is a recent publication in SOARD (Surgery for Obesity and Related Disorders). In this interesting article, the authors attempt to elucidate gastric bypass mechanism of action by studying gastric pouch solid food emptying. Altered gastro-intestinal motility is one of the most plausible mechanisms of action of weight loss surgery. Indeed, obesity and type 2 diabetes may be considered gastro-intestinal motility disorders resulting in abnormal post-prandial neuro-hormonal reaction to ingested food.
Several studies in the past have demonstrated that both gastric sleeve surgery and gastric bypass procedure increase gastric emptying and favor food dumping into the intestine stimulating the secretion of gut peptides like GLP-1 and PYY. In this article, the authors demonstrate the opposite; Increased gastric pouch emptying is associated with poor weight loss in a pilot study of 10 patients. The authors compared gastric pouch emptying in 5 gastric bypass patients with successful weight loss to a group of 5 gastric bypass patients with poor weight loss at least 2 years after surgery. they found that the faster emptying rate is mainly due to the first 15 minutes following food ingestion. The authors conclude that if their hypothesis is proven narrowing gastric pouch outlet may lead to decreased food emptying and as a result improved weight loss.
The idea of food retention in the stomach or gastric pouch leading to satiety and consequently weight loss is quite naïve. Gastric pouch outlet narrowing can only result in heartburn and esophageal dysmotility. We have had plenty of experience with this concept in Lap Band patients. We also know that endoscopic gastro-jejunostomy narrowing in the case of gastric bypass does not result in improved and durable weight loss. Accelerated food delivery into the intestines has been established in multiple studies evaluating gastric bypass and sleeve gastrectomy patients. Indeed, I have developed an effective surgery for gastroparesis based on these studies. I doubt that the results published by Deden et al will be reproducible by other investigators. Nonetheless, the authors raise an important question and studying gastro-intestinal motility in weight loss surgery patients will help elucidate some of the mechanisms of action underlying gastric bypass and sleeve gastrectomy.