It is a hormone that sends signals to the brain so that the sensation of appetite appears.
When there is no food in the stomach, the hormone ghrelin is released.
Ghrelin travels through the bloodstream to the brain , where it stimulates neurons in the hypothalamus to signal hunger.
The hypothalamus regulates hunger, thirst, mood, and other physical functions.
Ghrelin levels are highest just before eating.
Ghrelin serves many purposes, but the most common is its ability to stimulate appetite, causing an individual to digest more food and store more fat.
In fact, when artificially administered to humans, the amount of food intake increases by 30%.
The hormone plays a role in the hypothalamus, the part of the brain that controls appetite, and may also act in regions of the brain that control reward processing.
Ghrelin is often called the “hunger hormone” and has many other functions in the body.
Ghrelin plays a role in the function of the pituitary gland , where ghrelin receptors activate stimulation of the hormone.
Ghrelin appears to help control insulin release and plays a protective role in cardiovascular health, helps protect bones and muscles, and may even help against cancer.
This well balanced hormone has a job in many different body systems.
When ghrelin receptors in the hypothalamus interact with the hormone, it sends a strong signal to your body that your food supply is low and that you need to eat.
Then you start to feel hungry and other changes occur in the body such as:
- You start to conserve fat: Researchers know that ghrelin signals your body to decrease thermogenesis and the oxidation of brown fats in your fat cells. That means the body is burning less fat to save energy in the event of starvation.
- The stomach becomes more elastic: Scientists know that ghrelin increases “gastric motility” to help prepare your stomach to accept food and push food through the digestive tract.
- Appetite increases: Your brain continues to send signals that you are hungry until you start eating. After eating, ghrelin levels decrease for 1 to 3 hours.
Modification of ghrelin levels
Even though ghrelin can provide benefits in your body, many people are still frustrated by nagging hunger pangs and would like to reduce ghrelin to feel better.
The evidence on the factors that modify ghrelin in the body are as follows:
- Poor sleep increases ghrelin. Studies have shown that when you don’t get enough sleep, ghrelin levels increase. So being able to get a good night’s sleep helps to block ghrelin in the body. Sleep can also help you make more leptin, a hormone that helps you eat less.
- An empty stomach stimulates ghrelin. Because ghrelin production begins when your stomach is empty, you may be able to limit ghrelin by snacking or eating small meals throughout the day. But when the goal is to lose weight, choose snacks that help create a calorie deficit.
- Weight extremes such as obesity and anorexia alter ghrelin levels.
- Increased muscle mass: High amounts of muscle mass are associated with lower levels of ghrelin.
- Protein foods can help block ghrelin. A small study showed that higher protein foods suppressed ghrelin levels for a longer period of time. Lean proteins are a smart choice for dieters who want to build a leaner and stronger body.
On the market there are dietary supplements or ghrelin blockers to modify the levels of the hormone in the body.
Most of the supplements are made from herbs that help you feel a feeling of fullness so that the body does not respond to hunger signals and consume less food.
High-fiber foods, eating healthy, calorie-controlled meals throughout the day, provide the same benefit.
Problems associated with ghrelin
Because ghrelin affects appetite, it can affect weight loss, especially when someone is dieting.
When someone tightly controls calories, ghrelin levels rise.
This, then, causes the rebound of the lost pounds that occurs right after a diet for many people.
People struggling with anorexia nervosa may also have high levels of ghrelin, which occurs as part of the body’s natural response to hunger.
For patients with Prader-Willi syndrome, ghrelin levels in the blood are high.
This is believed to be the reason why these patients struggle with severe obesity and extreme hunger.
Ghrelin levels rise before obesity, so it is not caused by increased body weight.
On the other hand, patients who have gastric bypass surgery may have lower ghrelin levels than those who lose weight naturally.
This may be the reason why gastric bypass surgery, if the eating plan is strictly followed, has long-term effectiveness with regard to weight loss.