(HealthDay News) – Calorie reduction rather than the actual Roux-en-Y gastric bypass (RYGB) surgery seems to account for the improvement in glucose homeostasis in obese patients with type 2 diabetes who undergo RYGB, according to a study published online March 25 in Diabetes Care.

Ildiko Lingvay, MD, MPH, from the University of Texas Southwestern Medical Center in Dallas, and colleagues evaluated the contribution of caloric restriction vs. surgically induced changes to glucose homeostasis for 10 patients with type 2 diabetes (age, 53.2 years; body mass index, 51.2kg/m²) in two 10-day periods several months before and immediately after RYGB. Dietary intake was closely matched in the two periods, and patients served as their own controls.

The researchers found that during the presurgery period, the patients lost 7.3kg compared with 4kg during the postsurgery period (P=0.01 between periods). Daily glycemia was significantly lower in the presurgery vs. the postsurgery period (P=0.02 between periods). During both periods the improvements in the fasting and maximum poststimulation glucose and six-hour glucose area under the curve (primary outcome) were similar.

“Glucose homeostasis improved in response to a reduced caloric diet, with a greater effect observed in the absence of surgery as compared with after RYGB,” write the authors. “These findings suggest that reduced calorie ingestion can explain the marked improvement in diabetes control observed after RYGB.”

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