What is Ghrelin? The Hunger Hormone Explained

The human body is a complex system with various hormones working together to regulate various functions. One such hormone is ghrelin, often referred to as the "hunger hormone." Ghrelin plays a crucial role in regulating appetite, food intake, and body weight.

What is Ghrelin For?

Ghrelin, also known as lenomorelin, is a hormone produced in the gut that acts as a hunger stimulant. [1,2] It travels through the bloodstream to the brain, where it signals the body to feel hungry and seek out food. Ghrelin's primary function is to increase appetite, leading to the consumption of more food, higher calorie intake, and fat storage. It also influences other physiological processes, such as the sleep/wake cycle, reward-seeking behavior [3], taste sensation, and carbohydrate metabolism.

This hormone is primarily produced in the stomach and secreted when the stomach is empty. It then enters the bloodstream and affects a region of the brain called the hypothalamus, which plays a vital role in regulating hormones and appetite. The level of ghrelin in your body determines your hunger levels. [4] Higher levels of ghrelin make you feel hungrier, while lower levels contribute to a sensation of fullness, making it easier to consume fewer calories.

Does Ghrelin Make You Gain Weight?

Ghrelin levels tend to rise before a meal when the stomach is empty and decrease shortly after eating when the stomach is full. Contrary to popular belief, individuals with obesity may not have higher levels of ghrelin. Individuals with obesity may have altered ghrelin regulation which is a significant difference. Recent studies suggest that ghrelin levels are lower in people with obesity. [6] However, research has shown that individuals with obesity may be more sensitive to the effects of ghrelin, [7] which can lead to increased calorie intake. Regardless of weight, beginning a diet to lose weight triggers an increase in ghrelin levels as a natural response to prevent starvation. [8]

During a weight loss journey, appetite increases, while levels of the satiety hormone leptin decrease. Additionally, metabolic rate tends to decrease, [9] especially with prolonged calorie restriction. There are several reasons for this, one being that your body naturally makes you move less to conserve energy and you burn less calories through none excersise activity thermogenesis. These adaptations make it more challenging to lose weight and maintain it over time, as hormones and metabolism adjust to regain lost weight.

The Effects of Dieting on Ghrelin Levels

When embarking on a weight loss diet, ghrelin levels begin to rise within a day and continue to increase over the course of several weeks. A study involving individuals with obesity found that a low-calorie diet for 16 weeks resulted in significant increases in ghrelin levels. [10] Another study conducted on postmenopausal women following a low-calorie diet for eight weeks also demonstrated an increase in ghrelin levels during and after weight loss. However, it's important to note that a study on a bodybuilding diet showed a 40% increase in ghrelin levels during a six-month period. [11] Nevertheless, this finding is based on a single individual and requires further research .

These trends suggest that the longer the duration of the diet and the more body fat and muscle mass lost, the higher the ghrelin levels rise. Consequently, hunger intensifies, making weight maintenance more challenging.

Functions of Ghrelin

Ghrelin has several key functions in the body:

Appetite Regulation: The primary function of ghrelin is to increase appetite. It stimulates hunger and prompts individuals to seek out food, leading to increased food intake and calorie consumption. Ghrelin levels rise when the stomach is empty, signaling the brain that it's time to eat. [1]

Food Intake and Fat Storage: Ghrelin not only stimulates appetite but also promotes food intake and fat storage. When ghrelin binds to receptors in the brain, it triggers the release of hormones that increase food consumption and encourage the body to store excess calories as fat. [1]

Sleep/Wake Cycle: Ghrelin also plays a role in regulating the sleep/wake cycle. Studies have shown that disrupted sleep patterns can lead to increased ghrelin levels, which may contribute to heightened hunger and weight gain. With just a single night of sleep deprevation completely disregulating ghrelin in many cases. [12]

Metabolism: Ghrelin influences carbohydrate metabolism by affecting how the body processes and utilizes glucose. It stimulates the release of growth hormone from the pituitary gland, which aids in breaking down fat tissue and promoting muscle growth. [13]

Cardiovascular Health: Emerging research suggests that ghrelin has protective effects on cardiovascular health. Studies conducted on animal models have shown that ghrelin promotes vascular network expansion and reduces inflammation, indicating its potential role in maintaining a healthy cardiovascular system. [14]

Ghrelin and Appetite Regulation

Ghrelin is a crucial player in the regulation of appetite and body weight. It interacts with various hormones and pathways involved in hunger and satiety. One such hormone is leptin, which is responsible for signaling the brain when the body has enough energy stored and feels "full." While ghrelin increases appetite, leptin decreases it, creating a delicate balance between hunger and satiety.

When ghrelin levels rise, such as during fasting or before a meal, it stimulates the hypothalamus to increase appetite and food intake. On the other hand, when ghrelin levels decrease after a meal, it signals to the brain that hunger has been satisfied, promoting a feeling of fullness. [15]

Factors Affecting Ghrelin Levels

Several factors can influence ghrelin levels in the body. Understanding these factors can help in maintaining healthy ghrelin levels and supporting overall well-being. Here are some key factors that can affect ghrelin:

Diet and Meal Timing: Ghrelin levels rise when the stomach is empty or mostly empty. This increase in ghrelin signals hunger and prompts individuals to eat. Regular meal patterns and avoiding prolonged periods of fasting can help regulate ghrelin levels. [11,16]

Weight Changes: Rapid weight loss or drastic changes in body weight can impact ghrelin levels. Studies have shown that ghrelin levels increase during dieting, potentially contributing to increased appetite and weight regain. Maintaining a stable weight can help prevent these fluctuations in ghrelin levels. [11]

Sleep: Poor sleep quality or inadequate sleep duration has been associated with higher ghrelin levels. Lack of sleep can disrupt the balance of hunger-regulating hormones, including ghrelin and leptin, leading to increased appetite and food cravings. [12]

Muscle Mass: Higher amounts of muscle mass or fat-free mass have been linked to lower ghrelin levels. Regular exercise and strength training can help increase muscle mass and potentially contribute to the regulation of ghrelin levels. [17]

Stress: Chronic stress has been shown to affect ghrelin levels. In times of stress, ghrelin levels may increase, leading to heightened appetite and potentially unhealthy eating behaviors. Implementing stress management techniques, such as mindfulness and relaxation exercises, may help regulate ghrelin levels.Genetics: Some people simply produce more ghrelin than others, this is linked to genetic propensity to obesity. [18]

Maintaining Healthy Ghrelin Levels

While ghrelin levels can be influenced by various factors unfortunately there is no way to medicate around it directly, there are steps you can take to maintain healthy ghrelin levels. Here are some strategies to consider:

Adopt a Balanced Diet: Focus on consuming a diet rich in healthy slow release low gycemic index carbohydrates, lean proteins, and nutrient-dense foods. Avoid fad diets or extreme calorie restrictions, as these can disrupt ghrelin regulation and lead to rebound hunger.

Avoid Processed Foods: Limit your intake of processed foods, which are often high in added sugars, high-fructose corn syrup, and unhealthy fats. These foods can affect ghrelin levels and contribute to imbalances in hunger and satiety signals.

Prioritize Sleep: Aim for at least seven to eight hours of quality sleep each night. Establish a regular sleep routine and create a sleep-friendly environment to support optimal sleep duration and quality.

Stay Hydrated: Drink plenty of water throughout the day and consume water-rich foods, such as fruits and vegetables. Adequate hydration can help regulate ghrelin levels and support overall well-being.

Manage Stress: Implement stress management techniques, such as deep breathing exercises, meditation, or engaging in activities you enjoy. Chronic stress can disrupt ghrelin regulation, by increasing cortisol, the stress hormone leading to increased appetite and potentially unhealthy eating habits.

By adopting these lifestyle habits and maintaining a balanced approach to nutrition and wellness, you can support healthy ghrelin levels and promote overall well-being.

What is Ghrelin? Conclusion

Ghrelin, the "hunger hormone," plays a significant role in appetite regulation, food intake, and body weight. It signals to the brain that it's time to eat and increases appetite, prompting individuals to seek out food. Ghrelin also influences other physiological processes, such as sleep/wake cycles, reward-seeking behavior, taste sensation, and carbohydrate metabolism. Maintaining healthy ghrelin levels is important for overall well-being and weight management. By adopting a balanced diet, prioritizing sleep, staying hydrated, managing stress, and maintaining a stable weight, you can support optimal ghrelin regulation and promote a healthy relationship with food.

Remember, the human body is a complex system, and ghrelin is just one piece of the puzzle. It’s not the only hormone that plays a role in hunger, but it is often seen as the largest piece of this particular puzzle.


1 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4443295/

2 - https://www.ncbi.nlm.nih.gov/books/NBK547692/

3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5033008/

4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4049314/

5 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5819073/

6 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5756630/

7 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4814209/

8 - https://pubmed.ncbi.nlm.nih.gov/12023994/

9 - https://www.ncbi.nlm.nih.gov/books/NBK572145/

10 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8514378/

11 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4033492/

12 - https://pubmed.ncbi.nlm.nih.gov/18564298/

13 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5805851/

14 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823193/

15 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4924164/

16 - https://pubmed.ncbi.nlm.nih.gov/16469977/

17 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7328200/

18 - https://pubmed.ncbi.nlm.nih.gov/30714236/

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