Although weight loss can be tough, maintaining your weight after a diet is sometimes even harder.

In fact, research shows that a large percentage of dieters regain all the weight they’ve lost within just 1 year (1).

Weight regain is partially due to your appetite and weight-regulating hormones, which encourage your body to maintain and even regain fat (2, 3).

Ghrelin, the “hunger hormone,” plays a key role because, in addition to its several other important functions, it can signal to your brain that it’s time to eat (4).

Additionally, a 2020 study focused on people with type 2 diabetes found that a rise in ghrelin level was significantly involved in stimulating appetite, making it harder to lose weight (5, 6).

Here is everything you need to know about this hormone and how it can impact your weight.

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What is ghrelin?

Ghrelin is a hormone produced in your gut. It is often referred to as the “hunger hormone” and is sometimes called lenomorelin.

It travels through your bloodstream and to your brain, where it tells your brain to become hungry and seek out food.

Ghrelin’s main function is to increase appetite. It makes you consume more food, take in more calories, and store fat (4, 6).

In addition, it affects your sleep/wake cycle, reward-seeking behavior, taste sensation, and carbohydrate metabolism (4, 6).

This hormone is produced in your stomach and secreted when your stomach is empty. It enters your bloodstream and affects a part of your brain called the hypothalamus, which helps regulate your hormones and appetite (4, 7).

The higher your levels of ghrelin, the hungrier you get. The lower your levels, the more full you feel and the easier it is to eat fewer calories.

Therefore, if you want to lose weight, lowering your ghrelin levels can be beneficial.

Ghrelin may sound like a terrible, diet-wrecking hormone. However, in the past it played a role in survival by helping people maintain a moderate level of body fat (2).

These days, if you under-eat or have difficulty gaining weight, higher ghrelin levels may help you consume more food and calories per day.

Summary

Ghrelin is a hormone that sends a signal to your brain to feel hungry. It plays a key role in regulating calorie intake and body fat levels.

What causes ghrelin to rise?

Ghrelin levels typically rise before a meal, when your stomach is empty. Then they decrease shortly after, when your stomach is full (8).

While you might assume that people with obesity have higher levels of ghrelin, they may just be more sensitive to its effects. In fact, some research suggests ghrelin levels are actually lower in people with obesity (9).

Other research suggests that people with obesity may have an overly active ghrelin receptor, known as GHS-R, which leads to increased calorie intake (10, 11).

Regardless of your weight, ghrelin levels increase and make you hungry when you start a diet to try to lose weight. This is a natural response by your body, which tries to protect you from starvation.

During a weight loss diet, your appetite increases and your levels of the “fullness hormone” leptin go down. Your metabolic rate also tends to decrease significantly, especially if you restrict calories for long periods (12, 13).

These adaptations can make it significantly harder to lose weight and keep it off, as your hormones and metabolism adjust to try to regain the weight you’ve lost.

Summary

Ghrelin levels can rise during a weight loss diet, increasing hunger and making it harder to lose weight.

How your levels change during a diet

Within a day of beginning a weight loss diet, your ghrelin levels will start to go up. This change continues over the course of weeks.

One small study in people with obesity found that following a low calorie diet for 16 weeks led to significant increases in levels of ghrelin (14).

Another small 8-week study in 18 postmenopausal women on a low calorie diet showed that levels of ghrelin increased both during and after weight loss (15).

Plus, a 2013 study found that during a 6-month bodybuilding diet, which uses severe dietary restrictions to reach an extremely low level of body fat, ghrelin increased by 40%. However, these findings are based on only one person, so more extensive research is needed (16).

These trends suggest that the longer you diet — and the more body fat and muscle mass you lose — the higher your levels will rise.

As a result of that increase, you’ll get hungrier, so it will become much harder to maintain your new weight.

Summary

Ghrelin levels increase significantly on a weight loss diet. The longer the diet, the more your levels will increase.

How to lower ghrelin and reduce hunger

Ghrelin seems to be a hormone that can’t be directly controlled with drugs, diets, or supplements.

However, there are a few things you can do to help maintain healthy levels:

  • Maintain a moderate weight. Studies show that ghrelin levels increase during dieting (9).
  • Prioritize sleep. Poor sleep increases your levels of ghrelin and has been linked to increased hunger and weight gain (17, 18).
  • Increase muscle mass. Higher amounts of fat-free mass or muscle are associated with lower levels of ghrelin (4).
  • Eat more protein. A high protein diet increases fullness and reduces hunger. One of the mechanisms behind this is a reduction in ghrelin levels (19).
  • Maintain a stable weight. According to one older study of postmenopausal women, drastic weight changes and yo-yo dieting can disrupt key hormones, including ghrelin (20).
Summary

Maintaining a moderate weight, avoiding long dieting periods, eating more protein, and getting more sleep can help optimize your ghrelin levels.

The bottom line

Ghrelin is a very important hunger hormone.

It plays a major role in hunger, appetite, and food intake. Because of this, it can have major effects on your success in reaching and maintaining a moderate weight.

By having a sustainable and enjoyable diet plan, you can avoid the yo-yo dieting that causes large fluctuations in weight and negatively affects your hormones.

Just one thing

Try this today: In addition to ghrelin, several other hormones play key roles in regulating hunger and appetite. Check out this article for a full list, along with some simple steps you can take to keep your hormone levels in check.