A high-fat diet causes ghrelin resistance by triggering inflammation in the vagus nerve and hypothalamus, shutting down the hunger hormone's signaling pathway.
Complete ghrelin resistance12 weeks of high-fat diet eliminated all ghrelin signaling — food intake, vagal nerve activity, and brain activation — through inflammation-driven receptor loss
What the researchers found
Diet-induced obesity caused complete ghrelin resistance in mice — peripheral ghrelin injections failed to increase food intake, suppress oxygen consumption, activate the vagus nerve, or trigger signaling in the hypothalamus. The mechanism: a high-fat diet reduced ghrelin receptor expression in both the nodose ganglion (vagus nerve relay station) and the hypothalamus.
Critically, this resistance was driven by inflammation. The high-fat diet triggered activation of macrophages and microglia and upregulated inflammatory cytokines in both the nodose ganglion and hypothalamus, blunting ghrelin's ability to signal through the vagal afferent pathway that normally carries hunger signals from gut to brain.
Why it matters
Ghrelin is supposed to be the body's "hunger alarm," but this study shows obesity breaks that alarm through inflammation. This is analogous to leptin resistance — where obese individuals have high leptin but their brains stop responding to the "I'm full" signal. Understanding that ghrelin resistance and leptin resistance share an inflammatory mechanism helps explain why appetite regulation goes haywire in obesity and could point toward anti-inflammatory interventions.
The numbers in context
12 weeks of high-fat diet; ghrelin receptor mRNA reduced in nodose ganglion and hypothalamus; macrophage/microglia markers upregulated; inflammatory cytokines elevated; complete loss of ghrelin-induced food intake, vagal nerve activity, ERK2/AMPK phosphorylation, and hypothalamic Fos expression
How the study worked
Researchers fed mice a high-fat diet for 12 weeks to induce obesity, then tested multiple aspects of ghrelin signaling. They measured food intake response to subcutaneous ghrelin, oxygen consumption, vagal nerve electrical activity, intracellular signaling markers (ERK2 and AMPK phosphorylation) in the nodose ganglion, and Fos expression (a marker of neuronal activation) in the hypothalamus. They also measured ghrelin receptor mRNA levels and inflammatory markers in the nodose ganglion and hypothalamus.
Who was studied
C57BL/6 mice fed high-fat diet for 12 weeks
What this study cannot tell us
This is a mouse study, and high-fat diet-induced obesity in mice may not perfectly model human obesity. The 12-week timeframe is relatively short. The study doesn't establish whether reducing inflammation can restore ghrelin sensitivity. It does not address whether the findings apply to genetic forms of obesity versus diet-induced obesity.
How to read the evidence
This is a well-designed animal study with multiple complementary measurements demonstrating a clear mechanism. It provides moderate evidence for the inflammation-driven ghrelin resistance pathway, though translation to human obesity requires further research.
When this study was published
Published in 2015, this is a decade old but remains highly relevant. Ghrelin resistance is now recognized as a feature of obesity, and this study's identification of the inflammatory mechanism continues to inform current research.
The bigger picture
Ghrelin resistance joins leptin resistance as a key feature of the broken appetite regulation system in obesity. Just as leptin resistance means the brain can't hear the "I'm full" signal, ghrelin resistance means the hunger signaling system is also dysfunctional. The common thread is inflammation — the same chronic, low-grade inflammation that characterizes obesity disrupts multiple hormonal pathways. This inflammatory mechanism could be a target for therapies aimed at restoring normal appetite regulation.
Questions still open
- Could anti-inflammatory treatments restore ghrelin sensitivity in obese individuals and help normalize appetite regulation?
- Does ghrelin resistance contribute to the metabolic dysfunction of obesity, or is it primarily a consequence?
- How does ghrelin resistance interact with leptin resistance — do they compound each other's effects on appetite dysregulation?
Common questions
What is ghrelin resistance?
Is ghrelin resistance similar to insulin or leptin resistance?
Read the original research
Diet-induced obesity causes peripheral and central ghrelin resistance by promoting inflammation.
The Journal of endocrinology, 226(1), 81-92
Citation
Naznin, Farhana; Toshinai, Koji; Waise, T M Zaved; NamKoong, Cherl; Md Moin, Abu Saleh; Sakoda, Hideyuki; Nakazato, Masamitsu. (2015). Diet-induced obesity causes peripheral and central ghrelin resistance by promoting inflammation.. The Journal of endocrinology, 226(1), 81-92. https://doi.org/10.1530/JOE-15-0139