Accelerated Gastric Emptying but No Carbohydrate Malabsorption 1 Year After Gastric Bypass Surgery (GBP)

Following gastric bypass surgery (GBP), there is a post-prandial rise of incretin and satiety gut peptides. The mechanisms of enhanced incretin release in response to nutrients after GBP is not elucidated and may be in relation to altered nutrient transit time and/or malabsorption. Seven morbidly obese subjects (BMI = 44.5 +/- 2.8 kg/m(2)) were studied before and 1 year after GBP with a d-xylose test. After ingestion of 25 g of d-xylose in 200 mL of non-carbonated water, blood samples were collected at frequent time intervals to determine gastric emptying (time to appearance of d-xylose) and carbohydrate absorption using standard criteria. One year after GBP, subjects lost 45.0 +/- 9.7 kg and had a BMI of 27.1 +/- 4.7 kg/m(2). Gastric emptying was more rapid after GBP. The mean time to appearance of d-xylose in serum decreased from 18.6 +/- 6.9 min prior to GBP to 7.9 +/- 2.7 min after GBP (p = 0.006). There was no significant difference in absorption before (serum d-xylose concentrations = 35.6 +/- 12.6 mg/dL at 60 min and 33.9 +/- 9.1 mg/dL at 180 min) or 1 year after GBP (serum d-xylose = 31.5 +/- 18.1 mg/dL at 60 min and 27.2 +/- 11.9 mg/dL at 180 min). These data confirm the acceleration of gastric emptying for liquid and the absence of carbohydrate malabsorption 1 year after GBP. Rapid gastric emptying may play a role in incretin response after GBP and the resulting improved glucose homeostasis.