Changes in Fasting and Prandial Gut and Adiposity Hormones Following Vertical Sleeve Gastrectomy or Roux-en-Y-Gastric Bypass: an 18-Month Prospective Study

Background: Vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB) produce substantial weight loss, both primarily through gastric restriction but with potentially different hormonal signaling. This prospective, observational study compared changes in gut-derived hormones in VSG, RYGB, and weight-stable participants at 6 and 18 months post-surgery. Methods: Sixty-four obese, non-diabetic women, including 18 VSG, 23 RYGB, and 23 weight-stable controls completed assessments at baseline and 6 months, before and after consuming a mixed-nutrient meal; blood sampling occurred for 180 min post-meal. Fifty-one participants completed the 18-month outcome. Change from baseline in post-prandial area under the curve (over 180 min) for GLP-1, PYY_3–36, ghrelin, and leptin was measured at 6 and 18 months post-surgery. Results: At 18 months, VSG and RYGB participants lost a mean (±SEM) of 25.5 ± 2.3% and 34.2 ± 4.2% of initial weight, respectively (p < 0.156), which both differed (p < 0.001) from the +1.7 ± 1.0% gain in the control group. Fasting ghrelin declined significantly more in VSG than RYGB participants at both months 6 (p = 0.0199) and 18 (p = 0.0003). In response to the mixed-nutrient meal, GLP-1 and PYY_3–36 demonstrated an exaggerated post-prandial response that was significantly greater in RYGB than VSG at 6 months (p < 0.0001 and p = 0.0062, respectively) but not 18 months (p = 0.0296 and p = 0.1210). Conclusions: VSG and RYGB both produced substantial weight losses at 18 months. The data suggest a role of gastrointestinal hormones as mediators of weight loss.