boston – Rather than being a better strategy to block absorption of ingested calories, the future of bariatric surgery depends on treatment combinations that promote weight control through healthy physiology, according to three experts participating in a panel on this topic at the 2018 AGA Tech Summit, sponsored by the AGA Center for GI Innovation and Technology.
“When we think about the mechanisms of surgery, the mechanical model is dead. There is no good supporting evidence for the mechanical model. The current model is all physiological, involving changes in signaling from the gut to the rest of the body,” asserted Lee Kaplan, MD, PhD, AGAF, director of the Weight Center at Massachusetts General Hospital, Boston.
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The list of evidence suggesting that change in physiologic function is a far more important explanation for weight loss from bariatric interventions is long, according to Dr. Kaplan. Of his many examples, he noted that pregnant women gain weight normally after bariatric surgery.
“Now, if you cannot absorb food normally after bariatric surgery, how do you gain weight normally when pregnant?” Dr. Kaplan asked. The answer to this and other examples of a disconnect between a simple food-blocking mechanism and what is observed is that bariatric procedures favorably alter signals that control hunger, satiety, and metabolism.
The two other experts on the panel largely agreed. In discussing advances in small-bowel devices for the treatment of type 2 diabetes mellitus, Christopher Thompson, MD, AGAF, director of therapeutic endoscopy at Brigham and Women’s Hospital, Boston, also looked to physiologic effects of bariatric surgery. He placed particular emphasis on the foregut and hindgut hypotheses. These hypotheses are “not yet written in stone,” but they provide a conceptual basis for understanding metabolic changes observed after bariatric procedures.
“One way that gastric bypass might work is that it alters the incretins that drive insulin secretion and sensitivity,” Dr. Thompson said. The same principle has been proposed for a novel incisionless magnetic device developed by Dr. Thompson that is now in clinical trials. The device, which creates an anastomosis and a partial jejunal diversion, achieved a 40% excess weight loss and a significant reduction in hemoglobin A1c levels among patients with type 2 diabetes mellitus in an initial study. Dr. Thompson contended that this effect cannot be explained by a change in nutrient absorption.
