Highlights of the Annual Scientific Meeting of NAASO, The Obesity Society

October 20-24, 2006; Boston, Massachusetts

Heather K. Stein, MD, MPH


January 05, 2007

In This Article

Bariatric Surgery

Bariatric surgery remains the most effective treatment for weight loss and weight maintenance. The symposium on bariatric surgery detailed the current research of Lee Kaplan, MD,[11] Massachusetts General Hospital Weight Center, Boston, Massachusetts, and David E. Cummings, MD, University of Washington/VA Puget Sound Health Care System, Seattle, Washington.[12]

Dr. Kaplan described the clinical effects of Roux-en-Y gastric bypass (RYGB) in humans, including postoperative weight stability, a decrease in the intensity of hunger, an increase in the sensation of fullness, a decrease in the frequency and intensity of non-hunger-related desire to eat, and a change in taste preferences -- all of which suggest that the surgery has an effect on the central nervous system. On the basis of rat and mouse models of RYGB, Dr. Kaplan revealed that the surgery results in a decrease in food intake and a relative increase in energy expenditure, which is reflected in the observed increase in body temperature after surgery. In these animal studies, there was no change in caloric absorption. Dr. Kaplan concluded that the decrease in food intake and increase in energy expenditure after RYGB reflects the ability of the surgery to reset the body's energy set point at a lower body mass index (BMI). He also stated that the metabolic effects and weight loss from the surgery are likely mediated through the central nervous system.

Dr. Cummings offered 2 theories for the mechanisms of weight loss and diabetes improvement after RYGB: the foregut and hindgut hypotheses. The foregut hypothesis suggests that the bypass of the duodenum and proximal jejunum after RYGB, or the lack of food exposure to these areas of the small intestine, might be a mechanism through which weight loss and improvement in glucose tolerance are achieved. This theory is supported by the work of Dr. Francisco Rubino,[13] of the University of Strasbourg, France, who has shown that bypass of the duodenum results in improvement of diabetes in rats. The hindgut hypothesis focuses on the expedited delivery of nutrients to the ileum after RYGB. Dr. Cummings suggested that this early exposure of nutrients causes decreased gastrointestinal motility, improvement in diabetes, and weight loss. It results in the accentuated production of peptides produced by L cells in the distal small intestine, including glucagon-like peptide (GLP)-1, peptide YY, and oxyntomodulin, which may be responsible for these physiologic effects. Furthermore, given that GLP-1 is an incretin hormone that regulates and improves glucose homeostasis, it may be a significant factor in the improvement in glucose homeostasis after RYGB.

The following presentations on bariatric surgery were also made during the conference:

  • At the bariatric surgery symposium, Eric Finkelstein, PhD, of RTI International, Research Triangle Park, North Carolina, discussed a pre- and postsurgical analysis of payments for insured patients receiving bariatric surgery.[14] He concluded that laparoscopic adjustable gastric band (LAGB) is likely to be cost-saving within 9 years after surgery, whereas RYGB is likely to be cost-saving 18 years after surgery.

  • An abstract from Adams and colleagues[15] compared health outcomes after 2 years among RYGB patients, patients with severe obesity who sought RYGB but were denied by their insurance carriers, and patients with severe obesity who did not seek RYGB surgery. Compared with the 2 nonsurgical groups, RYGB patients had statistically significant improvements in BMI, waist circumference, percentage of body fat, systolic blood pressure, glucose, total cholesterol, triglycerides, low-density lipoprotein (LDL) cholesterol, insulin, A1C, apnea-hypopnea index, and quality-of-life parameters.

  • Surgical programs vary in their requirement for weight loss prior to bariatric surgery. A poster presented by Alger-Mayer and colleagues[16] described research suggesting a significant correlation between weight loss prior to RYGB and sustained weight loss 3 years after RYGB. The study authors suggested, therefore, that weight loss prior to surgery might predict long-term weight-loss success.

The intensive efforts of researchers to better understand the mechanism of weight-loss surgery will yield information to further explain the complex physiology of weight regulation. This information may result in the development of medications or nonsurgical devices that, either alone or in combination, might replicate the physiologic effects of weight-loss surgery and result in similar sustained weight loss.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.