THURSDAY, July 8 (HealthDay News) -- Improvements in insulin resistance that occur in the first week after Roux-en-Y gastric bypass (RYGB) surgery appear to be due mostly to caloric restriction, according to research published in the July issue of Diabetes Care.
James M. Isbell, M.D., of the Vanderbilt University School of Medicine in Nashville, Tenn., and colleagues administered a mixed meal to nine patients before RYGB and again after the procedure, and to nine matched obese controls before and after four days on a calorie-restricted diet similar to the post-surgery diet, to see what influence calorie restriction has on the improvements in metabolic response that occur soon after surgery, before substantial weight loss.
The researchers found that neither group lost much weight, an average 1.4 kg in the surgery group (P = 0.46) and 2.2 kg in the caloric restriction group (P = 0.004). In both groups, insulin resistance improved, and insulin response to the mixed meal was blunted -- though this occurred without a glucose response change. The surgery group experienced an increase in glucagon-like peptide 1 levels that peaked after eating, but incretin responses did not change with caloric restriction.
"These data suggest that an improvement in insulin resistance in the first week after RYGB is primarily due to caloric restriction, and the enhanced incretin response after RYGB does not improve postprandial glucose homeostasis during this time," the authors write.
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