Context: The mechanisms underlying weight loss after Roux-en-Y gastric bypass (RYGBP) are not well understood.

Objective: The objective of the study was to assess the changes in active glucagon-like peptide 1 (GLP-1) and total peptide YY (PYY) after RYGBP and examine their relationship with changes in hunger and satiety.

Design: This was a prospective study on the changes in active GLP-1, PYY, hunger, and satiety in response to a standardized test meal in nine normal-glucose-tolerant obese subjects [body mass index (BMI) 47.4 ± 6.1 kg/m²] before and 6 wk after RYGBP.

Results: Before surgery, meal ingestion failed to stimulate GLP-1 and PYY secretion. Six weeks after surgery, despite subjects still being markedly obese (BMI 43.6 ± 7.8 kg/m²), the area under the curve_0–120′ of GLP-1 and of PYY in response to the standardized test meal were significantly elevated (P < 0.05 and P < 0.01, respectively). These hormonal responses were significantly larger (P < 0.01) than those observed in a group matched for the BMI attained 6 wk after surgery. The 2.9 ± 1.2- and 1.6 ± 1.9-fold increase, respectively, in the area under the curve_0–120′ of GLP-1 and PYY were accompanied by a significant decrease in fasting (P < 0.05) and postprandial hunger (P = 0.05) and a significant increase in satiety (P < 0.05) after meal intake. Nevertheless, a significant correlation between changes in the hormonal and eating behavior parameters was not found.

Conclusion: Our data show that RYGBP is associated with an improvement in the active GLP-1 and total PYY response to a liquid-meal intake. Moreover, we provide circumstantial evidence for a potential role of these gastrointestinal hormones on the decreased appetite after RYGBP.