Rapid improvements in diabetes after gastric bypass surgery may be related to decreased calorie ingestion alone and not surgically induced hormonal changes, according to investigators.

The finding is based on a prospective study of 10 patients with type 2 diabetes who underwent Roux-en-Y gastric bypass (RYGB) surgery. The study was divided into pre-surgery and post-surgery periods. Each period involved a 10-day inpatient stay. In both periods, patients had a perfectly matched calorie-restricted diet and equivalent physical activity and intravenous fluid administration. The investigators, led by Ildiko Lingvay, MD, MPH, of the University of Texas Southwestern Medical Center in Dallas, measured glucose every four hours throughout the study.

Results showed that daily glycemia was significantly lower in the pre-surgery than post-surgery period (1,293.58 vs. 1,478.80 mg/dL), the researchers reported online ahead of print in Diabetes Care. Patients lost 7.3 kg during the pre-surgery period compared with 4.0 kg during the post-surgery period.

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“These findings support the hypothesis that rapid diabetes resolution after RYGB is mediated by caloric restriction and that there is no need to invoke a direct hormonally mediated mechanism related to bypassing the duodenum,” the authors wrote.