The short-chain fatty acid propionate, produced by gut bacteria from dietary fiber, triggers release of appetite-suppressing GLP-1 and PYY through a specific receptor in the colon.
Both GLP-1 and PYY elevatedPropionate simultaneously triggered release of two key appetite-suppressing hormones, and the effect was abolished when the FFA2 receptor was knocked out
What the researchers found
Propionate — a short-chain fatty acid produced by gut bacteria when they ferment dietary fiber — triggered the simultaneous release of both GLP-1 and PYY (two appetite-suppressing peptide hormones) from the colon in rats and mice. This effect was mediated through the free fatty acid receptor 2 (FFA2): when the researchers repeated the experiments in mice genetically engineered to lack FFA2, propionate's ability to stimulate gut hormone release was significantly impaired both in isolated cell cultures and in live animals.
The study confirmed this through multiple approaches: propionate stimulated GLP-1 and PYY secretion from cultured colon cells, and when infused directly into the colon of live rodents, it elevated both hormones in portal vein and jugular vein blood.
Why it matters
This study provides a mechanistic explanation for why high-fiber diets suppress appetite — the fiber gets fermented into propionate by gut bacteria, which then triggers the same satiety hormones (GLP-1 and PYY) that blockbuster weight loss drugs target. Understanding this pathway could lead to dietary or prebiotic strategies that naturally boost the body's own appetite-suppressing peptides.
The numbers in context
Both GLP-1 and PYY elevated in portal + jugular vein plasma · FFA2 knockout significantly attenuated the response · Effects confirmed in vitro and in vivo
How the study worked
The researchers used three complementary approaches: (1) isolated colonic crypt cell cultures from wild-type and FFA2 knockout mice to test propionate's direct effect on hormone secretion in vitro; (2) intra-colonic infusion of propionate in live Wistar rats with blood sampling from jugular and portal veins; and (3) the same in vivo protocol in wild-type and FFA2 knockout C57BL6 mice to confirm the receptor's role.
Who was studied
Wistar rats, wild-type C57BL6 mice, and FFA2 knockout mice
What this study cannot tell us
This is a rodent study — the magnitude of propionate's effect on GLP-1 and PYY may differ in humans. The study uses direct colonic infusion, which bypasses normal digestion and may produce higher local concentrations than dietary fiber fermentation. The study doesn't measure actual appetite or food intake, only hormone levels.
How to read the evidence
This is a well-designed mechanistic animal study using both in vitro and in vivo approaches with knockout mouse validation. The multi-method approach strengthens confidence, but the findings are in rodents and have not been confirmed in human clinical studies.
When this study was published
Published in 2015, this study has become a widely cited reference in the gut microbiome–appetite regulation field. The core finding about propionate and FFA2-mediated GLP-1 release has been supported by subsequent research.
The bigger picture
The GLP-1 drug revolution has focused on synthetic receptor agonists, but this study reveals a natural upstream trigger: gut bacteria converting fiber into propionate, which then stimulates the body's own GLP-1 production. This connects the dots between the gut microbiome, diet, and the incretin hormone system — and suggests that optimizing gut bacteria or delivering propionate directly could complement or partially substitute for pharmaceutical GLP-1 drugs.
Questions still open
- Could dietary propionate supplementation or prebiotic fiber meaningfully increase GLP-1 levels enough to affect appetite and weight in humans?
- Do people with obesity have reduced FFA2 receptor expression, potentially explaining impaired satiety signaling from fiber-rich diets?
- Could targeting the FFA2 receptor with synthetic agonists offer a new approach to stimulating natural GLP-1 release without injectable drugs?
Common questions
Can eating more fiber boost your GLP-1 levels naturally?
What is FFA2 and why does it matter for appetite?
Read the original research
The short chain fatty acid propionate stimulates GLP-1 and PYY secretion via free fatty acid receptor 2 in rodents.
International journal of obesity (2005), 39(3), 424-9
Citation
Psichas, A; Sleeth, M L; Murphy, K G; Brooks, L; Bewick, G A; Hanyaloglu, A C; Ghatei, M A; Bloom, S R; Frost, G. (2015). The short chain fatty acid propionate stimulates GLP-1 and PYY secretion via free fatty acid receptor 2 in rodents.. International journal of obesity (2005), 39(3), 424-9. https://doi.org/10.1038/ijo.2014.153