Hunger Hormones: What Are Ghrelin and Leptin?

Key Takeaways

• Ghrelin and leptin are the body’s main hunger-regulating hormones, controlling appetite and fullness.

• Ghrelin, produced in the stomach, stimulates hunger and reduces energy expenditure.

• Leptin, released from fat cells, signals fullness but may become less effective in obesity due to leptin resistance.

• Poor sleep, stress, and high-fat diets can disrupt ghrelin and leptin balance, leading to increased appetite and weight gain.

• Balanced nutrition, regular exercise, good sleep, and stress management can help regulate hunger hormones and support weight management.

What are Hunger Hormones?

When it comes to hunger, balance is key. Your body needs to get enough energy to fuel itself, but not so much food that it can negatively impact your health.

Hunger hormones are released by the body to tell you when to eat and when you're full. The two main hormones involved in regulating hunger and fullness are called ghrelin (the hunger hormone) and leptin (the satiety hormone).

Knowing how these hormones work can help you to understand the role they play in weight management.

What is Ghrelin?

Ghrelin is the hormone that's responsible for appetite stimulation. It's mostly released from the stomach and small intestine, but also from the brain and other areas of the body in small amounts. Ghrelin is released when the stomach is empty and stops being released after food intake.

By working on the ghrelin receptor in the brain, ghrelin makes you feel hungrier, meaning you're more likely to eat.

But it's not all about hunger. Ghrelin is also important for energy homeostasis (otherwise known as energy balance within the body) and promotes fat storage. As levels of ghrelin increase, the body also tries to reduce energy expenditure. This means moving less, and that your body burns less energy to keep you warm.

Alongside its role in energy and appetite regulation, ghrelin also stimulates growth hormone release. Growth hormone helps to regulate lipid metabolism, bone density, muscle structure, and maintain various structures within the body.

What is Leptin?

Leptin is another hormone that helps to manage hunger and energy metabolism. Leptin is released from fat cells and the cells in the small intestine. Leptin production is related to body fat levels, and it stops the fat storage levels in your body from becoming too high or too low.

Leptin also activates areas of the brain that make you feel fuller and less motivated to eat. Leptin levels are often high in severe obesity, despite there being too much fat stored within the body. One explanation for this is that the body becomes resistant to leptin, meaning the body no longer responds to high leptin levels as it should.

How Ghrelin and Leptin Work Together

Both ghrelin and leptin are necessary for normal energy balance within the body. In simple terms, if ghrelin levels rise, this stimulates appetite and increases food intake, whilst leptin acts by increasing feelings of fullness. If these hormone levels are out of balance, appetite, body weight, and energy homeostasis can all be affected.

Many factors can upset this delicate balance, including poor sleep, stress, high-fat diets, genetic disorders, and hormonal changes such as menopause.

Impact on Weight Management

Ghrelin's Role in Weight Gain and Loss

Ghrelin levels are increased when fasting and decreased after a meal in response to the rising glucose and insulin release that come after eating.

There is mixed evidence on how diet affects the ghrelin system. Some studies show that a high-fat diet and being obese can reduce ghrelin levels, but other studies have found that a high-fat diet can increase the number of cells that produce ghrelin.

Losing weight often leads to increased ghrelin levels, which can make it harder to continue to lose weight. This is because your body is suddenly getting less energy than normal. You may even be expending more energy in the form of exercise.

To compensate, your body increases ghrelin production, but increasing levels of ghrelin can make you feel hungrier, crave certain foods, and it may be more difficult to continue to lose weight.

Interestingly, despite losing weight, people who have had gastric bypass surgery don't experience an increase in ghrelin release. This may partly explain why the procedure is an effective option for people who've struggled to lose weight using other methods.

Leptin's Role in Controlling Weight

Evidence suggests there's a relationship between body fat percentage and levels of leptin in the blood.

In anorexia nervosa, leptin levels are low due to low fat stores in the body. In obesity, leptin is released in very high amounts by the fat cells as a response to excessive fat storage. However, in some individuals, the body doesn't respond appropriately to the high levels of leptin. The hormone isn't effective at making individuals feel full, leading to increased food intake and weight gain.

Leptin resistance may be due to genetic mutations in the leptin receptor or because certain areas in the brain become desensitised to leptin and fail to respond appropriately.

Factors Affecting Ghrelin and Leptin Levels

Many things impact hunger hormone levels, including genetics, hormones, surgery, underlying health conditions, and lifestyle factors. Let's focus on some of the things that are within your control.

Sleep and Its Effect on Hunger Hormones

When the body doesn't get enough sleep, your hunger hormones can be thrown out of balance. In a study of 44 sleep-deprived adults, lack of sleep led to increased ghrelin levels and decreased leptin levels. A review of 21 studies also found that short sleep duration is linked to increased ghrelin and decreased leptin. This may explain why many people with poor sleep experience an increase in appetite.

Sleep is important for many areas of health, so if you're struggling to get enough sleep, it may be a good idea to seek help from a medical professional. Read more about sleep disorders and how to improve your sleep on the NHS website.

Diet and Nutritional Intake

A review of the literature found that a diet high in sugar, fat, carbohydrates, and low in fibre is related to increased leptin resistance. A reduced-calorie diet that contains a higher proportion of protein can reduce resistance levels and help with weight loss.

Ghrelin production may be suppressed for longer after eating high-fat and high-protein meals when compared to meals that are high in carbohydrates. This means you may feel fuller for longer after eating meals that are balanced and contain fats and proteins.

Stress and Its Impact on Hormonal Balance and Weight

Ghrelin levels are known to increase in response to high levels of stress, meaning stress can make you feel hungry.

When stressed, the body goes into fight or flight mode, causing an increase in the production of the stress hormone cortisol. High cortisol levels stimulate the production of ghrelin, but can also lead to emotional eating and make someone more likely to opt for unhealthy foods.

By managing your stress levels, you can avoid the spike in cortisol (and the increase in ghrelin that follows).

Ghrelin, Leptin, and Menopause – What You Need to Know

It's common for postmenopausal women to struggle with their weight, and falling oestrogen levels may be related to this. Low oestrogen is linked to decreased levels of leptin and may also contribute to leptin resistance. Declining oestrogen also impacts fat distribution, leading to more fat deposited within the abdomen ,which in turn can increase the risk of cardiovascular disease.

Ghrelin is also impacted by oestrogen levels, but the relationship is more complicated. Lack of oestrogen during the menopause can increase ghrelin levels, leading to increased appetite and changes in food preferences. However, there's some evidence that increased oestrogen also leads to ghrelin release.

These changes in hunger hormones may lead menopausal women to feel hungrier and to experience weight gain. During this time, it's more important than ever to eat a healthy, balanced diet and exercise regularly. Learn more about how diet and exercise contribute to weight loss here: https://www.nhs.uk/better-health/lose-weight/

The Role of Weight Loss Treatments in Hormone Regulation

Mounjaro and Wegovy are two popular weight loss injections that are licensed for obese individuals with a BMI of 30 or more (or above 27 if they have a weight-related health condition). Although these medications may not directly affect ghrelin and leptin levels, they do impact hunger levels.

Both medications mimic the hormone glucagon-like peptide 1 (GLP-1), and Mounjaro is also similar in structure to the hormone glucose-dependent insulinotropic polypeptide (GIP) and can affect blood glucose levels.

By mimicking GLP-1 (and GIP for Mounjaro), both Mounjaro and Wegovy can increase feelings of fullness and reduce hunger.

Alongside regular exercise and a healthy diet plan, these medications can be effective for weight loss. However, they should only be used alongside lifestyle changes and under medical supervision.

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Summary: Ghrelin, Leptin, and Their Role in Hunger and Weight Loss

Ghrelin and leptin are two important hormones for hunger and energy regulation. Leptin increases feelings of fullness, whilst ghrelin increases hunger.

An imbalance between the hormones can lead you to feel hungrier and gain weight. However, by eating balanced meals, exercising regularly, managing your stress, and sleeping well, you can help to keep the natural balance between the two hormones.