Physiology, not mechanics, explains benefit of bariatric procedures

 

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.

Robert Lodge/MDedge News

Essentially all bariatric surgery and bariatric endoscopic devices block or restrict absorption of food in an effort to achieve weight loss by mechanically obstructing food absorption. However, Dr. Kaplan said mechanics do not explain what is observed clinically.

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 A_1c 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.

 

A surgeon serving on the panel, Marina Kurian, MD, of New York University’s Langone Medical Center, New York, also referenced the evidence for physiologic effects when speaking about gastric bypass and sleeve gastrectomy. Although both involve a blocking function for food absorption, she agreed that there are several reasons why this may not account for benefits.

“Certainly with gastric bypass, we talk about foregut and hindgut theory in terms of incretin effect,” Dr. Kurian said. She also noted that even the procedures that produce the greatest restriction on food absorption are not typically effective as a single therapeutic approach. Rather, her major point was that no approach, whether surgical, endoscopic, or lifestyle, is generally sufficient to achieve and maintain weight loss indefinitely. In her own practice, she has been moving to a “one-stop shopping” approach to coordinate multiple options.

“Those of us working in obesity are very aware of its chronicity and how one intervention is not enough,” Dr. Kurian said. She suggested that coordinated care among surgeons, gastroenterologists, dietitians, behavioral therapists, and others will provide the road forward even if the next set of surgical procedures or endoscopic devices are incrementally more effective than current options for weight loss.

One reason that a single intervention may not be enough is that obesity is not a single disease but the product of multiple different pathological processes, according to Dr. Kaplan. This is supported by the varied response to current therapies. Producing a variety of examples, he showed that, although there are large weight reductions with the most successful therapies, some patients are exceptional responders, while a proportion of patients lose little or no weight and others actually gain weight. He expressed doubt that there will be a single solution applicable to all patients.

 

“Patients who respond to one therapy may not respond to another and vice versa, and so the goal is to match each patient with the therapy that is most appropriate and protective for them,” Dr. Kaplan said.

GIs are uniquely positioned to lead a care team to help patients with obesity achieve a healthy weight. The POWER (Practice Guide on Obesity and Weight Management, Education and Resources) white paper provides physicians with a comprehensive, multidisciplinary process to guide and personalize innovative obesity care for safe and effective weight management.

Learn more at http://www.cghjournal.org/article/S1542-3565(16)309880/fulltext.

 

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.

Robert Lodge/MDedge News

Essentially all bariatric surgery and bariatric endoscopic devices block or restrict absorption of food in an effort to achieve weight loss by mechanically obstructing food absorption. However, Dr. Kaplan said mechanics do not explain what is observed clinically.

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 A_1c 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.

 

A surgeon serving on the panel, Marina Kurian, MD, of New York University’s Langone Medical Center, New York, also referenced the evidence for physiologic effects when speaking about gastric bypass and sleeve gastrectomy. Although both involve a blocking function for food absorption, she agreed that there are several reasons why this may not account for benefits.

“Certainly with gastric bypass, we talk about foregut and hindgut theory in terms of incretin effect,” Dr. Kurian said. She also noted that even the procedures that produce the greatest restriction on food absorption are not typically effective as a single therapeutic approach. Rather, her major point was that no approach, whether surgical, endoscopic, or lifestyle, is generally sufficient to achieve and maintain weight loss indefinitely. In her own practice, she has been moving to a “one-stop shopping” approach to coordinate multiple options.

“Those of us working in obesity are very aware of its chronicity and how one intervention is not enough,” Dr. Kurian said. She suggested that coordinated care among surgeons, gastroenterologists, dietitians, behavioral therapists, and others will provide the road forward even if the next set of surgical procedures or endoscopic devices are incrementally more effective than current options for weight loss.

One reason that a single intervention may not be enough is that obesity is not a single disease but the product of multiple different pathological processes, according to Dr. Kaplan. This is supported by the varied response to current therapies. Producing a variety of examples, he showed that, although there are large weight reductions with the most successful therapies, some patients are exceptional responders, while a proportion of patients lose little or no weight and others actually gain weight. He expressed doubt that there will be a single solution applicable to all patients.

 

“Patients who respond to one therapy may not respond to another and vice versa, and so the goal is to match each patient with the therapy that is most appropriate and protective for them,” Dr. Kaplan said.

GIs are uniquely positioned to lead a care team to help patients with obesity achieve a healthy weight. The POWER (Practice Guide on Obesity and Weight Management, Education and Resources) white paper provides physicians with a comprehensive, multidisciplinary process to guide and personalize innovative obesity care for safe and effective weight management.

Learn more at http://www.cghjournal.org/article/S1542-3565(16)309880/fulltext.

 

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.

Robert Lodge/MDedge News

Essentially all bariatric surgery and bariatric endoscopic devices block or restrict absorption of food in an effort to achieve weight loss by mechanically obstructing food absorption. However, Dr. Kaplan said mechanics do not explain what is observed clinically.

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 A_1c 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.

 

A surgeon serving on the panel, Marina Kurian, MD, of New York University’s Langone Medical Center, New York, also referenced the evidence for physiologic effects when speaking about gastric bypass and sleeve gastrectomy. Although both involve a blocking function for food absorption, she agreed that there are several reasons why this may not account for benefits.

“Certainly with gastric bypass, we talk about foregut and hindgut theory in terms of incretin effect,” Dr. Kurian said. She also noted that even the procedures that produce the greatest restriction on food absorption are not typically effective as a single therapeutic approach. Rather, her major point was that no approach, whether surgical, endoscopic, or lifestyle, is generally sufficient to achieve and maintain weight loss indefinitely. In her own practice, she has been moving to a “one-stop shopping” approach to coordinate multiple options.

“Those of us working in obesity are very aware of its chronicity and how one intervention is not enough,” Dr. Kurian said. She suggested that coordinated care among surgeons, gastroenterologists, dietitians, behavioral therapists, and others will provide the road forward even if the next set of surgical procedures or endoscopic devices are incrementally more effective than current options for weight loss.

One reason that a single intervention may not be enough is that obesity is not a single disease but the product of multiple different pathological processes, according to Dr. Kaplan. This is supported by the varied response to current therapies. Producing a variety of examples, he showed that, although there are large weight reductions with the most successful therapies, some patients are exceptional responders, while a proportion of patients lose little or no weight and others actually gain weight. He expressed doubt that there will be a single solution applicable to all patients.

 

“Patients who respond to one therapy may not respond to another and vice versa, and so the goal is to match each patient with the therapy that is most appropriate and protective for them,” Dr. Kaplan said.

GIs are uniquely positioned to lead a care team to help patients with obesity achieve a healthy weight. The POWER (Practice Guide on Obesity and Weight Management, Education and Resources) white paper provides physicians with a comprehensive, multidisciplinary process to guide and personalize innovative obesity care for safe and effective weight management.

Learn more at http://www.cghjournal.org/article/S1542-3565(16)309880/fulltext.