Study identifies factors associated with poor weight loss after gastric bypass surgery

Individuals with diabetes and those whose stomach pouches are larger appear less likely to successfully lose weight after gastric bypass surgery, according to a report in the September issue of Archives of Surgery, one of the JAMA/Archives journals. Roux-en-Y gastric bypass surgery is the most common bariatric procedure in North America, according to background information in the article. During the procedure, surgeons create a smaller stomach pouch that restricts food intake and bypasses large sections of the digestive system. "When performed in high-volume centers and with a low rate of complications, gastric bypass provides sustained and meaningful weight loss, significant improvement in quality of life, improvement or resolution of obesity-associated comorbidities and extended life span," the authors write. "However, 5 percent to 15 percent of patients do not lose weight successfully, despite perceived precise surgical technique and regular follow-up."

Guilherme M. Campos, M.D., and colleagues at the University of California, San Francisco, examined data from 361 patients who underwent gastric bypass at one institution between 2003 and 2006. Poor weight loss was defined as losing 40 percent or less of excess body weight after 12 months and good weight loss as losing more than 40 percent of excess weight.

Twelve-month follow-up data were available for 310 of the patients, who had an average body mass index (BMI) of 52 before surgery. At follow-up, they had an average BMI of 34 and had lost an average of 60 percent of their excess body weight. A total of 38 patients (12.3 percent) had poor weight loss. After adjusting for other related factors, diabetes and having a larger size of the stomach pouch after gastric bypass surgery were independently associated with poor weight loss.

Individuals with diabetes may take insulin or other drugs that stimulate the production of fat and cholesterol, the authors note. "Other factors that may lead to weight gain in patients with diabetes include a 'protective' increase in caloric intake to treat episodes of hypoglycemia [low blood sugar], reduction of urinary glucose losses and sodium and water retention that are a direct effect of insulin on the distal tubule in the kidney," the authors write.

The restriction on dietary intake imposed by a small stomach pouch is one of the most important aspects of gastric bypass surgery, they note. Surveys suggest that many surgeons estimate pouch size using anatomical landmarks rather than using a sizing balloon. "As the use of gastric bypass continues to grow, we believe it is critical to stress the importance of and to teach the creation of the small gastric pouch and to better standardize the technique used for pouch creation," the authors write.

"We conclude that gastric bypass provides good or excellent weight loss for most patients," they continue. "However, diabetes mellitus and larger pouch size are independently associated with poor weight loss after gastric bypass. Changes in the use of diabetes medications may reduce the risk of poor weight loss among diabetics undergoing gastric bypass. Detailed attention to the creation of a small gastric pouch is essential for achieving the best results."

Source: JAMA and Archives Journals