Why Some People Regain Weight After Gastric Bypass: Gut Hormone Differences 13 Years Later | Research

The takeaway

Patients with suboptimal weight loss 13 years after gastric bypass had lower fasting ghrelin and a weaker post-meal satiety hormone response compared to those who maintained optimal weight loss.

13+ years post-RYGB
The longest follow-up comparison of gut hormone profiles between optimal and suboptimal weight loss outcomes after gastric bypass

What the researchers found

Patients with optimal weight loss (OWL) after RYGB had higher basal acylated ghrelin and greater post-meal GLP-1 responses (iAUC) compared to those with suboptimal weight loss (SWL) and controls. OWL patients also had lower post-meal ghrelin responses (iAUC) — meaning ghrelin dropped more after eating, signaling better satiety.

Both surgical groups showed elevated PYY and CCK post-meal responses compared to controls. Prospective food consumption ratings were lower in OWL than SWL. Total weight loss correlated positively with GLP-1 responses and negatively with hunger and desire-to-eat ratings, suggesting gut peptide signaling plays a key role in long-term weight maintenance after surgery.

Why it matters

Understanding why some patients maintain weight loss while others regain is critical for improving bariatric surgery outcomes. This study provides the longest follow-up comparison of gut hormone profiles after RYGB, suggesting that the appetite hormone system — particularly GLP-1 signaling — may determine long-term success. This could guide the development of targeted hormonal therapies for patients experiencing weight regain.

How the study worked

Cross-sectional comparison of 50 RYGB patients from the BAROBS study (25 SWL, 25 OWL) at 13+ years post-surgery, plus 25 non-surgical controls. Fasting and post-meal plasma concentrations of acylated ghrelin, GLP-1, PYY, and CCK were measured alongside subjective appetite ratings (hunger, fullness, desire to eat, prospective food consumption). Area under the curve analysis was used for postprandial responses.

What this study cannot tell us

This was a cross-sectional observational study, so causality cannot be established — it's unclear whether the hormone differences caused the weight outcomes or resulted from them. Pre-surgical hormone levels were not available for comparison. The sample size (50 surgical patients) is relatively small. Dietary habits, physical activity, and psychological factors that influence weight were not comprehensively assessed.

How to read the evidence

This is a cross-sectional observational study comparing hormone profiles at a single time point. While the 13-year follow-up is impressive and the sample includes appropriate controls, the design cannot establish whether hormone differences are causes or consequences of weight outcomes.

When this study was published

Published in 2024, this is a very current study addressing an increasingly important clinical question as the long-term bariatric surgery patient population grows and GLP-1-based medications become more widely available.

The bigger picture

This study connects to the explosive growth in GLP-1-based obesity treatments. The finding that better GLP-1 responses predict long-term weight maintenance after surgery provides biological rationale for combining GLP-1 receptor agonists (like semaglutide) with bariatric surgery in patients experiencing weight regain — an approach now being actively studied in clinical trials.

Questions still open

Could GLP-1 receptor agonists rescue weight regain in post-RYGB patients by compensating for their blunted endogenous GLP-1 response?
Why do some patients maintain robust gut hormone responses 13 years post-surgery while others do not?
Would pre-surgical gut hormone profiling help predict which patients are at risk for suboptimal long-term outcomes?

Common questions

What gut hormones control appetite after gastric bypass?

Several peptide hormones from the gut regulate appetite after gastric bypass: GLP-1 and PYY signal fullness after eating, CCK helps trigger meal-ending satiety, and ghrelin stimulates hunger. After RYGB, the rapid delivery of food to the lower gut dramatically increases GLP-1 and PYY release, which is thought to be a key mechanism of weight loss. This study found that patients who maintained their weight loss had stronger GLP-1 responses.

Could GLP-1 drugs like semaglutide help people who regain weight after bariatric surgery?

This study provides biological support for that idea. Patients with weight regain had weaker endogenous GLP-1 responses after eating, suggesting their bodies weren't producing enough of this satiety signal. GLP-1 receptor agonists could potentially compensate for this deficit, and clinical trials testing this approach are already underway.

Read the original research

Suboptimal Weight Loss 13 Years After Roux-en-Y Gastric Bypass Is Associated with Blunted Appetite Response.

Obesity surgery, 34(2), 592-601

View on PubMed ↗Publisher’s paper ↗

Citation

Nymo, Siren; Lundanes, Julianne; Eriksen, Kevin; Aukan, Marthe; Rehfeld, Jens Frederik; Holst, Jens Juul; Johnsen, Gjermund; Græslie, Hallvard; Kulseng, Bård; Sandvik, Jorunn; Martins, Catia. (2024). Suboptimal Weight Loss 13 Years After Roux-en-Y Gastric Bypass Is Associated with Blunted Appetite Response.. Obesity surgery, 34(2), 592-601. https://doi.org/10.1007/s11695-023-07028-w