Ghrelin is a hormone produced mainly by the stomach and plays a central role in regulating appetite and energy balance. It also supports the release of growth hormone (GH) and helps stimulate normal intestinal movement.
This hormone fluctuates throughout the day, increasing during fasting and decreasing after meals. Because of this pattern, ghrelin strongly influences hunger signals sent to the brain.
Changes in ghrelin levels are associated with nutritional status, body weight, and certain medical conditions. Understanding how ghrelin works helps explain its role in hunger, digestion, and weight regulation.
Main functions of ghrelin
The main functions of ghrelin are:
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Stimulate appetite, increasing food intake
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Increase body fat by promoting fat storage and reducing fat use and breakdown
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Support the release of GH, a hormone involved in growth and muscle formation
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Stimulate natural intestinal movements, helping prevent constipation
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Facilitate the release of gastric acids, improving digestion
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Inhibit insulin release, leading to higher blood glucose levels
Because ghrelin stimulates hunger, reduces protein breakdown, and limits weight loss, it has also been studied as a potential treatment option for severe weight loss, such as that seen in cancer or age-related muscle mass loss.
Normal ghrelin values
Ghrelin levels vary depending on the time of the test and whether weight loss has occurred, as shown below:
In people with normal weight, average ghrelin levels range from 520 to 700 pg/mL.
Adults who have undergone bariatric surgery typically show much lower ghrelin levels, with average blood values of up to 120 pg/mL.
Ghrelin levels are measured through a blood test, which may be requested by a physician or nutritionist. For accurate results, fasting for 10 to 12 hours before the test is required.
When ghrelin may be high
Ghrelin levels are usually higher during fasting, when the body produces more of this hormone to stimulate hunger. For this reason, it is normal for ghrelin levels to rise before meals.
Levels may also be elevated in conditions such as Prader-Willi syndrome or in cases of malnutrition, including anorexia or cachexia. This increase acts as a protective mechanism to encourage food intake and weight gain.
What low ghrelin means
Ghrelin levels naturally decrease in the blood shortly after eating.
People with obesity also tend to have lower ghrelin levels. This is believed to occur because frequent high food intake reduces the body’s sensitivity to ghrelin, leading to decreased hormone production as body weight increases.
Relationship between ghrelin and leptin
Ghrelin and leptin are hormones with opposite effects that help the brain assess nutritional needs. Together, they are essential for maintaining the balance between hunger and satiety and supporting weight stability.
While ghrelin increases the sensation of hunger, leptin promotes satiety and signals when to stop eating. As leptin levels rise, ghrelin levels tend to decrease.
How to reduce ghrelin
Some strategies that may help control ghrelin include:
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Maintaining a healthy diet with foods rich in fiber and lean protein, such as fruits, vegetables, whole grains, and white meats
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Keeping a stable, healthy weight and avoiding repeated cycles of weight gain and loss, known as the yo-yo effect
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Limiting excessive intake of high-fat foods, including full-fat cheeses, whole milk and yogurt, beef, margarine, ice cream, French fries, and pizza
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Eating regular meals to avoid prolonged fasting and excessive increases in ghrelin
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Engaging in regular physical activity, such as running, dancing, strength training, or swimming
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Reducing intake of foods high in added sugars, such as glucose syrup, sugar, fruit juice, soft drinks, milk chocolate, fruits in syrup or crystallized fruits, processed cookies, and industrialized sauces
Adequate sleep is also important for ghrelin regulation. Sleeping 7 to 9 hours per night is recommended, as insufficient sleep can raise ghrelin levels in the body.