Both Roux-en-Y gastric bypass and sleeve gastrectomy significantly boost postmeal GLP-1 and PYY release while speeding up stomach emptying, though each procedure affects gut transit differently.
GLP-1 and PYY significantly increased after both surgeriesThese are the same satiety and blood-sugar-regulating peptides targeted by popular weight-loss medications like semaglutide
What the researchers found
Both Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) produced significant weight loss and dramatically increased postprandial secretion of the distal gut peptides GLP-1 and PYY — hormones involved in satiety and blood sugar regulation. Gastric emptying was significantly accelerated after both procedures.
A notable difference emerged: oro-cecal transit time (how fast food travels from mouth to large intestine) was significantly accelerated after SG but not after RYGB. Despite the parallel increases in peptide release and faster motility, no significant correlations were found between changes in gut peptide levels, changes in GI motility, and clinical outcomes like weight loss.
Why it matters
Understanding how bariatric surgery reshapes gut peptide signaling helps explain why these procedures work beyond simple stomach restriction. The surge in GLP-1 and PYY after surgery mirrors the mechanism of popular weight-loss drugs like semaglutide, suggesting the gut hormone response is central to sustained weight management. The differences between the two surgeries in transit time and peptide patterns could eventually help clinicians match patients with the procedure most likely to benefit them.
How the study worked
This was a prospective single-center study following 28 severely obese individuals before surgery and at 2 and 12 months after either RYGB or SG. At each time point, participants ate a standardized 459 kcal solid meal, and blood samples were taken to measure GLP-1, PYY, ghrelin, insulin, and glucose. Gastric emptying was assessed with a 13C octanoic acid breath test, and oro-cecal transit time was measured via lactulose hydrogen breath testing. Satiation was tracked using visual analog scale (VAS) scores.
What this study cannot tell us
The sample size of 28 patients is relatively small, which limits statistical power to detect correlations between peptide changes and clinical outcomes. The study was conducted at a single center, which may limit generalizability. The follow-up period of 12 months, while informative, does not capture longer-term hormonal adaptation that may occur years after surgery. The 459 kcal standardized meal may not reflect typical post-surgical eating patterns.
How to read the evidence
This is a prospective clinical study with objective measurements at multiple time points, but the small sample size (n=28), single-center design, and lack of randomization limit the strength of the evidence.
When this study was published
Published in 2025, this is a very recent study reflecting current surgical techniques and measurement methods.
The bigger picture
This study adds to the growing body of evidence that bariatric surgery's success is driven not just by anatomical restriction but by profound changes in gut hormone signaling — the same pathways targeted by GLP-1 receptor agonist drugs. By comparing two of the most common procedures head-to-head over a year, the research highlights that while both surgeries activate the 'ileal brake' (a feedback loop involving distal gut peptides), the specific patterns of hormonal and motility changes differ, which may have implications for long-term outcomes and personalized surgical recommendations.
Questions still open
- Do the differences in gut peptide patterns between RYGB and SG translate into different long-term weight loss or metabolic outcomes?
- Why were there no significant correlations between peptide changes and motility changes despite both being significantly altered?
- Would longer follow-up reveal further adaptation or normalization of gut hormone responses?
Common questions
What are GLP-1 and PYY, and why do they matter after bariatric surgery?
What's the main difference this study found between gastric bypass and sleeve gastrectomy?
Read the original research
Changes in gastrointestinal motility and gut hormone secretion after Roux-en-Y gastric bypass and sleeve gastrectomy for individuals with severe obesity.
Clinical obesity, 15(2), e12721
Citation
Wilbrink, Jennifer A; van Avesaat, Mark; Nienhuijs, Simon W; Stronkhorst, Arnold; Masclee, Ad A M. (2025). Changes in gastrointestinal motility and gut hormone secretion after Roux-en-Y gastric bypass and sleeve gastrectomy for individuals with severe obesity.. Clinical obesity, 15(2), e12721. https://doi.org/10.1111/cob.12721