Ghrelin: Your Brain, Gut, and Hunger Hormones

Ghrelin, also known as the hunger hormone, increases appetite and supports other body functions. The stomach releases ghrelin and sends a signal to an area of the brain called the hypothalamus. Reducing ghrelin may reduce hunger and appetite.

This article will discuss how ghrelin works in the gut and brain, how high and low ghrelin levels occur, and ways to reduce ghrelin at home.

people eating burgers

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Main Function of Ghrelin in Gut and Brain

Ghrelin is a hormone that is primarily made in the stomach. Around mealtimes, ghrelin levels increase, then decrease after eating. It is a part of the gut-brain axis and sends signals through the vagus nerve and travels through the blood to the brain.

Within the gut, the main functions of ghrelin are:

  • Secretion of gastric acid
  • Gastric motility
  • Pancreatic protein output

In the brain, ghrelin sends signals to the hypothalamus to increase appetite. The hypothalamus is an area in the brain that produces hormones that control several body functions.

Ghrelin affects more than just the brain and the gut. It also performs the following functions:

  • Inhibiting insulin secretion
  • Maintaining glucose levels
  • Possibly playing a role in improving outcomes after heart attacks
  • Possibly reducing muscle atrophy by increasing food intake and activating the growth hormone
  • Regulating bone formation

What Is the Gut-Brain Axis?

The gut-brain axis is a bidirectional communication line between the central nervous system (including the brain) and the gut. There is research that suggests the microbiome within the gut can affect the brain and its chemistry.

How Low and High Ghrelin Levels Work

Ghrelin levels fluctuate throughout the day. It is primarily activated when the stomach is empty and stops after someone has eaten.

When you are fasting or have not eaten for a period of time, ghrelin secretion is increased and sends signals to the hypothalamus to stimulate hunger. After you have eaten, ghrelin secretion is reduced.

The types of food you eat can also affect ghrelin levels. When carbohydrates and proteins are eaten, less ghrelin is released into the bloodstream than when fats are consumed.

How Stress Affects Ghrelin

Ghrelin and stress are closely related. Research shows that ghrelin reduces stress. When you are stressed, ghrelin levels increase. This is thought to be a way in which the body adjusts to stressful states to prevent excessive anxiety.

Ways to Reduce Ghrelin While Increasing Leptin

Some people may try to reduce their ghrelin levels and increase leptin to decrease appetite, lose weight, or keep weight off.

There is no clear-cut evidence if this works. A 2014 literature review was inconclusive if ghrelin and leptin levels were associated with the ability to lose or keep weight off.

You can try to reduce ghrelin by doing the following:

  • Healthy diet: Ghrelin levels increase when someone has an empty stomach. Eating a healthy diet with carbs and protein may reduce ghrelin levels.
  • Sleep: Getting adequate sleep can maintain normal levels of ghrelin and leptin. A 2023 study found even one night of sleep deprivation increased ghrelin and decreased leptin levels.
  • Manage stress: Stress increases ghrelin levels. Keeping stress at bay may lower ghrelin levels.

Are Some People More Susceptible to Ghrelin Fluctuations?

Certain health conditions and health states can cause ghrelin fluctuations.

People who have obesity may have higher ghrelin levels. This can make them feel hungry more often and lead to weight gain.

Bariatric surgery has been shown to decrease ghrelin levels, which may also help people maintain their postsurgical weight loss.

Dieting increases ghrelin levels. When someone eats less, their ghrelin levels will increase in response to encouraging eating.

High Ghrelin and Always Hungry: Next Steps to Take

If you constantly feel hungry, contact a healthcare provider. It is important to explore possible medical conditions that may be contributing you your increased feeling of hunger.

If there is no known medical cause, then examine your lifestyle. Are you eating appropriately sized, healthy meals at regular times? Are you getting enough sleep and managing stress? Work on these three areas to reduce ghrelin and hunger.

Summary

Ghrelin is a hormone secreted by the stomach. It increases appetite, regulates insulin, and helps with bone formation, and several other body functions. Ghrelin reduction is sometimes sought after to help lose weight or maintain weight loss. While there is no solid evidence this works, there are a few ways to try to keep ghrelin levels down. This includes managing stress, eating a healthy diet, and getting adequate sleep.

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By Patty Weasler, RN, BSN
Patty is a registered nurse with over a decade of experience in pediatric critical care. Her passion is writing health and wellness content that anyone can understand and use.