Understanding Ghrelin: The Hunger Hormone and Its Functions
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Ghrelin is a hormone your stomach makes that signals your brain when your stomach is empty and it is time to eat [1]. Often called the "hunger hormone," its levels rise between meals and fall after you eat, but it does much more than trigger hunger: it also affects fat storage, growth hormone release, digestion, and cardiovascular health [1]. Understanding what raises and lowers ghrelin can help you make sense of hunger cues and weight management.
Quick Answer
Ghrelin is a hormone made mainly in the stomach that signals the brain's hypothalamus that it is time to eat. It peaks right before meals and drops after eating, and also promotes fat storage and growth hormone release. Dieting and weight loss raise it, which may explain weight loss plateaus. Good sleep and balanced meals may help. [1]
What the research says
Dieting raises ghrelin, and it stays raised. In a trial of 50 overweight or obese adults who lost an average of 13.5 kg on a 10-week very-low-energy diet, ghrelin rose significantly and was still higher than before weight loss about a year later, along with increased hunger (Sumithran et al., New England Journal of Medicine, 2011 [2]).
Short sleep pushes ghrelin up. In a small crossover study of 12 healthy young men, two days of restricted sleep raised ghrelin by 28% and lowered leptin, a fullness hormone, by 18%, while hunger rose 24% and appetite 23% (Spiegel et al., Annals of Internal Medicine, 2004 [3]).
Weight-loss surgery does not change ghrelin the same way. A meta-analysis of 53 articles found that ghrelin fell significantly after sleeve gastrectomy, while fasting ghrelin rose after Roux-en-Y gastric bypass; the authors caution that the effects on patients are complicated (Gu et al., Surgery for Obesity and Related Diseases, 2021 [4]).
What is ghrelin and where is it made?
Ghrelin (pronounced "GREL-in") is a hormone your stomach makes. Smaller amounts are also released by the brain, small intestine, and pancreas [1]. It acts as a communication link between the digestive system and the brain.
When your stomach is empty or nearly empty, it releases ghrelin into the bloodstream. The hormone travels to the hypothalamus, the part of the brain that helps keep your body in balance, and signals that it is time to eat. Once you eat and your stomach fills, ghrelin levels decrease [1].
What does ghrelin do?
Ghrelin is a multi-purpose hormone that helps your body acquire and store energy efficiently. Its key functions include:
Appetite signaling: alerts the hypothalamus when your stomach is empty so you feel hungry [1].
Fat storage: promotes the storage of body fat to maintain energy reserves [1].
Growth hormone release: makes the pituitary gland release growth hormone [1].
Digestion: helps move food from the stomach through the small and large intestines [1].
Blood sugar control: helps control insulin release and triggers the pancreas to release glucagon [1].
Ghrelin also plays a role in protecting cardiovascular health, learning and memory, stress, mood and anxiety, and the sleep-wake cycle (circadian rhythm). Scientists are still studying all the ways it affects the body [1].
What affects ghrelin levels?
Ghrelin levels are not fixed. They change with your meals, your body composition, your eating habits, and certain medical conditions.
Conditions linked to lower ghrelin
Ghrelin tends to be lower in people with obesity than in people with more muscle mass. Some researchers think people with obesity may be naturally more sensitive to the hormone, so they can feel very hungry even at lower levels [1]. Certain digestive conditions are also linked to low ghrelin:
Chronic gastritis: long-term inflammation of the stomach lining.
Functional dyspepsia: persistent indigestion without an obvious cause.
H. pylori infection: a bacterial infection that can damage the stomach lining.
Irritable bowel syndrome (IBS): a common disorder of the large intestine [1].
People who have gastric bypass surgery may also have lower levels [1], although the research above shows that the effect differs depending on the type of surgery.
Conditions linked to higher ghrelin
Ghrelin rises when you limit calories. After you lose weight by restricting calories, ghrelin levels increase, which may explain why it is hard to keep losing weight from dieting. This is known as the weight loss plateau [1]. High ghrelin is also associated with:
Anorexia nervosa: an eating disorder marked by extreme calorie restriction.
Cachexia: a condition in which the muscles waste away.
Celiac disease: an immune reaction to gluten that damages the small intestine.
Inflammatory bowel disease (IBD).
Prader-Willi syndrome: a genetic disorder that causes a constant sense of hunger [1].
How can I balance ghrelin?
Providers do not test ghrelin levels when assessing weight management progress, but certain habits may help keep ghrelin and other hormones healthier [1]. No specific food suppresses ghrelin; in general, eating foods high in healthy carbohydrates, such as whole grains, and lean proteins, such as chicken or fish, may help lower it [1].
Avoid yo-yo dieting: stay away from fad diets that cause frequent weight swings.
Prioritize protein: include lean protein, such as chicken or fish, in your meals.
Limit processed foods: cut back on foods high in sugar, high-fructose corn syrup, and salt.
Protect your sleep: sleep at least seven to eight hours every night.
Stay hydrated: drink plenty of water and eat water-rich fruits and vegetables.
Manage stress: stress may increase ghrelin, so find techniques that work for you [1].
When should you see a healthcare provider?
If you have obesity or are having difficulty losing weight, talk to a healthcare provider. Many factors affect weight, and abnormal ghrelin levels could be one of them. Also see a provider if you have persistent hunger that feels extreme or different from your normal, as it could be a sign of certain health conditions [1].
Bottom line
Ghrelin is far more than a hunger hormone. It coordinates energy intake, fat storage, and several other body processes, from digestion to cardiovascular protection and memory. By understanding what makes ghrelin rise and fall, you can make informed choices about sleep, food, and stress to support your metabolic health.
Your next step: if hunger feels extreme or weight management is a struggle despite consistent effort, schedule a consultation with a healthcare professional for a personalized plan.
FAQ
What is ghrelin?
Ghrelin is a hormone made mainly in the stomach that tells your brain when you are hungry.
Is ghrelin the only hunger hormone?
Ghrelin is the main hormone that stimulates hunger. It works alongside other hormones, such as leptin, that signal fullness.
Where is ghrelin produced?
Most ghrelin is made in the stomach. Smaller amounts come from the brain, small intestine, and pancreas.
When are ghrelin levels highest?
Ghrelin levels are typically highest right before mealtimes, when the stomach is empty or mostly empty, and fall after you eat.
Does obesity cause high ghrelin?
Surprisingly, people with obesity often have lower ghrelin levels. Some researchers think they may be more sensitive to the hormone, so they can feel very hungry even at lower levels.
Can dieting increase hunger?
Yes. Restricting calories and losing weight raises ghrelin, which can make it harder to keep losing weight. This is one explanation for the weight loss plateau.
How can I lower my ghrelin levels?
Eating lean protein and healthy carbohydrates, sleeping seven to eight hours a night, staying hydrated, avoiding yo-yo dieting, limiting processed foods, and managing stress may help keep ghrelin and other hormones healthier. No specific food suppresses ghrelin.
Does sleep affect ghrelin?
Yes. Sleeping at least seven to eight hours a night helps keep ghrelin and other hormone levels healthier, and in one small study two days of restricted sleep raised ghrelin by 28%.
What is the weight loss plateau?
The weight loss plateau is a stage where weight loss stalls, often because ghrelin rises after you lose weight by restricting calories, which increases hunger.
Do doctors test ghrelin levels?
Healthcare providers do not usually test ghrelin levels when assessing weight management progress. They look at your symptoms and weight loss strategies instead.
When should I see a provider about hunger?
See a provider if you have obesity, have trouble losing weight, or have persistent hunger that feels extreme or different from your normal. It could be a sign of certain health conditions.
Related Reading
Leptin: The Hormone Regulating Long-Term Weight and Satiety explains the fullness hormone that works opposite to ghrelin.
Obesity: Symptoms, Causes, Complications and Treatment — A Complete Guide covers the causes, health risks and treatment of obesity.
Prader-Willi Syndrome Guide: Symptoms, Causes, Diagnosis, and Treatment describes a genetic condition with constant hunger and high ghrelin levels.
GLP-1 Agonists: A Comprehensive Guide to Diabetes and Obesity Management explains medicines that reduce appetite and help with weight loss.
References
Cleveland Clinic. Ghrelin. Cleveland Clinic. February 18, 2026. https://my.clevelandclinic.org/health/body/22804-ghrelin
Sumithran P, Prendergast LA, Delbridge E, et al. Long-term persistence of hormonal adaptations to weight loss. New England Journal of Medicine. 2011;365(17):1597-1604. PMID 22029981. https://doi.org/10.1056/NEJMoa1105816
Spiegel K, Tasali E, Penev P, Van Cauter E. Brief communication: sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Annals of Internal Medicine. 2004;141(11):846-850. PMID 15583226. https://doi.org/10.7326/0003-4819-141-11-200412070-00008
Gu L, Lin K, Du N, et al. Differences in the effects of laparoscopic sleeve gastrectomy and laparoscopic Roux-en-Y gastric bypass on gut hormones: systematic and meta-analysis. Surgery for Obesity and Related Diseases. 2021;17(2):444-455. PMID 33249084. https://doi.org/10.1016/j.soard.2020.10.018
Medical disclaimer
This article is for general informational purposes and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional about any medical condition.
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