Insulin sensitivity improved with calorie-restricted diet without weight loss after bariatric surgery

New data suggest that caloric restriction without substantial weight loss is important for rapid improvements in insulin sensitivity within 1 week after Roux-en-Y gastric bypass.

Researchers found a 25% improvement in insulin sensitivity within the first week after Roux-en-Y gastric bypass before any significant weight loss.

The study included patients at a Vanderbilt University Medical Center surgical weight loss center. Researchers compared 9 patients who underwent gastric bypass with 9 patients who participated in a calorie-restricted diet comparable to a post-surgery diet, including fluid for 3 days. All participants were observed at baseline and again 4 days after open or laparoscopic bariatric surgery or after a calorie-restricted diet.

Both groups experienced similar minimal reductions in weight loss (surgery, 2.4 kg; diet, 2.2 kg) and in insulin resistance, as measured by homeostasis model assessment of insulin resistance (HOMA-IR: surgery, 5; diet, 4.8).

In response to a mixed meal, insulin response was blunted in both the surgery and diet groups, with no change in glucose response.

Glucagon-like peptide-1 levels increased after gastric bypass surgery and further increased after a mixed meal.

“Early alterations in the incretin response can be attributed to the surgery; however, the enhanced incretin response does not seem to have any additional benefit beyond caloric restriction on glucose homeostasis and insulin sensitivity,” the researchers wrote.

Isbell JM. Diabetes Care. 2010;33:1438-1442.