Background: Data from studies conducted in animal models suggest that intestinal glucose uptake and metabolism are upregulated after Roux-en-Y gastric bypass (RYGB) surgery, which contributes to a weight-loss-independent improvement in glycemic control.

Objective: We conducted a cohort study to evaluate whether an increase in gastrointestinal metabolism of ingested glucose occurs in obese people who underwent RYGB compared with those who underwent laparoscopic adjustable gastric banding (LAGB).

Design: A mixed meal containing stable isotope-labeled glucose was used to determine the gastrointestinal (small intestine and liver) retention, and presumably metabolism, of ingested glucose in obese subjects before and after matched weight loss (∼21%) induced by RYGB (n = 16) or LAGB (n = 9).

Results: The total percentage of ingested glucose that appeared in the systemic circulation was slightly lower after than before RYGB (85% ± 9% and 90% ± 8%, respectively) but was slightly higher after than before LAGB (89% ± 3% and 85% ± 4%, respectively) (P-interaction < 0.05). Accordingly, gastrointestinal clearance of ingested glucose (cumulative percentage cleared over 6 h postprandially) increased after RYGB (from 10% ± 8% before to 15% ± 9% after surgery) but decreased after LAGB (from 15% ± 4% before to 11% ± 3% after surgery) (P < 0.05). Surgery-induced weight loss caused a similar decrease in the 6-h postprandial plasma glucose area under the curve in both RYGB and LAGB groups (-4% ± 9% and -6% ± 5%, respectively; P = 0.475).

Conclusions: These data support the notion that intestinal glucose disposal increases after RYGB surgery. However, the magnitude of the effect was small and did not result in weight-loss-independent therapeutic effects on postprandial glycemic control. 

This trial was registered at clinicaltrials.gov as NCT00981500.