The Ghrelin Factor: The Science Behind Post-Diet Weight Rebound

By Patrick Zitt, DC, MS, DNM

Have you ever gone on a restrictive diet and lost 10lbs, 20lbs, or even more?? Were you surprised at how quickly the weight came back on?

This is such a common scenario that there is a well-known term for the endless cycle of losing weight and gaining it back: yo-yo dieting.

In fact, one study of obese participants showed that approximately 30-35% of lost weight was regained within 1 year and 50% of participants regained all lost weight by 5 years (1).

You may assume post diet weight gain is solely due to a loss of will power. Or binging after you "fall off the wagon" is just the result of missing your favorite treats after a long restriction.

And while the psychology of dieting may play, there is actually a physiological reason that contributes to the return of lost pounds: Ghrelin.

What Is Ghrelin?

Ghrelin is a growth hormone. Hormones are the body’s messengers. They are chemicals that travel through the blood stream on a mission to communicate between organs and tissues, and are responsible for hundreds of processes in the body.

There are two hormones that regulate hunger and satiety: Ghrelin and Leptin. While leptin is responsible for appetite suppression, ghrelin increases appetite and promotes calorie consumption. Thus, it has been aptly nicknamed the “hunger hormone”.

Ghrelin is produced by ghrelinergic cells in the gastrointestinal tract and secreted into the blood stream when the stomach is empty (2,3). It is carried to the hypothalamus (part of the brain) where there are high concentrations of ghrelin receptors (4,5,6,7).

Remember that ghrelin is a messenger? The message it carries from your empty stomach to your brain is to eat!

The emptier your stomach, the more ghrelin is released, and the hungrier you’ll become. After you have eaten and your stomach is full, ghrelin levels will drop and you’ll feel a sense of satiety (leptin plays a role here too) (8).

To those struggling to lose weight, ghrelin may sound like the root of all evil. However, historically, this hormone is responsible for keeping humans alive! It motivated us to search for food in times and places where it was scarce. It tells babies to cry out for nourishment. Even in our modern lives, it keeps blood sugar balanced by prodding us to eat lunch when we would otherwise not be bothered.

There is more to ghrelin than hunger signaling. It is also involved in learning and memory, gut motility and gastric acid secretion, sleep/wake rhythm, reward seeking behavior, taste sensation, and glucose metabolism (17). Ghrelin affects the immune system, the reproductive system, blood pressure and heart rate, neurogenesis, strengthens the bones, and promotes muscle development (9).

It is an important piece to our physiological puzzle, provided it is kept in balance.

How Ghrelin Encourages Weight Gain After A Diet

So ghrelin is a neat hormone that kept our ancestors and babies alive and plays a key role in several other processes. But that doesn’t stop it from being a thorn in the side of someone who has worked hard to bring their weight into balance just to find the pounds coming back on.

There are several ways in which the hunger hormone encourages a hefty appetite post diet.

1. Firstly, ghrelin is just doing its job! Its primary role is to increase appetite when the stomach is empty. Most weight loss diets involve either calorie restriction or time restrictions which leave one hungry. (6,10). The body cannot distinguish between dieting and starvation, and so its first response to weight loss is to do whatever it can to prevent starvation. (11)

2. In addition to the normal amount of ghrelin that is secreted while dieting, additional ghrelin is released in response to stress. Deep calorie restriction is a form of stress on the body. When following a low calorie diet, you are participating in two activities that encourage an increased appetite!
3. Our ancestors may have gone days or weeks without a filling meal and relied on fat stores to provide energy during those times. Despite the change in our modern reality, ghrelin is still programmed to increase secretion when our body fat percentage drops. The more fat you lose, the more your body goes into survival mode, signaling for greater food intake (12).
4. At times, ghrelin can override the signals that tell us to stop eating, like the ones triggered by the stomach's expansion. This may be a sign that ghrelin is not functioning as designed and warrants further investigation from a medical professional.
5. Gherlin levels have been shown to increase the first day of calorie restriction, continue to rise for several more weeks if restriction is continued, and can stay elevated for weeks after calories are no longer restricted (13,14).
6. When administered directly to the brain, ghrelin caused an immediate release of dopamine, the chemical associated with reward. Researchers hypothesize that the connection between the hunger hormone and the brain’s reward center is a survival mechanism to encourage us to seek food (15). Unfortunately, in a world where food is abundantly available and increasingly addictive, the feeling of satisfaction after a meal can contribute to overeating.

Ghrelin And Obesity

If ghrelin secretion increases in those with a low body fat percentages and decreases in those with higher body fat percentages, it would stand to reason that people with obesity would have a lower appetite. And yet, that is not the case. Why?

It is thought that while people with obesity do indeed have lower ghrelin levels, they may be more sensitive to its effects or have an over active ghrelin receptor (16,18,19). There is likely a genetic component that explains this but further research is needed.

What Increases Ghrelin?

Fasting

An empty stomach is the primary trigger for the production and secretion of ghrelin (20).

Fiber and resistant starch

Those that eat more fiber and/or resistant starch may produce more ghrelin on an empty stomach than those who eat a low fiber/RS diet (21,22). Note that fiber is a healthy, necessary part of the diet and plays an important role in weight loss. Please do not reduce your fiber intake in an attempt to lower ghrelin secretion!

Low body fat

The less body fat you have, the more ghrelin you will produce, as the body believes it is in danger without adequate fat stores (23,24).

Lack of sleep

Just one night of low sleep can increase ghrelin levels. Likely, when there is a lack of energy from sleep, our bodies will attempt seek energy through calories (25).

Stress

Ghrelin is secreted at higher levels in times of stress and even for some time after. While there is not a definitive reason why, presumably it is an attempt to gather energy to fight whatever stressors lie ahead (26).

What Reduces Ghrelin?

There are certainly those who, either by genetics or condition, struggle to gain weight and need increased ghrelin. But the majority of people today are likely looking to balance their weight by decreasing their hunger signals.

Please note that the strategies described below are natural, safe ways to balance this hormone. It is unwise to attempt to dramatically or artificially suppress ghrelin.

Eat the right amount of food

Ghrelin is stimulated and secreted when the stomach is empty. If you are severely limiting your food intake, you will find yourself consistently hungry (27), setting you up for the yo-yo effect. Of course, if you are attempting to lose weight, you will likely need to curb your food intake by some degree.

A good goal to aim for is to eat enough food in one sitting to reduce hunger for about three hours. If you are getting hungry sooner, you may not be eating enough.

Eat enough protein

While the primary trigger for ghrelin release is quantity of food, the type of food you consume has influence, particularly protein. Studies have shown that a diet high in protein promotes a feeling of fullness, even with calorie restriction. The researchers discovered that meals rich in protein influenced glucose-dependent insulinotropic polypeptides, which played a role in the response of ghrelin. Furthermore, the protein-rich meals were better at delaying the emptying of the stomach, which extended satiety. (28).

Protein needs will vary by sex, weight, age, activity level. You can assess your protein needs by using an online calculator that takes these into account. From there, pay attention to your hunger cues. If you are getting hungry less than three hours after your last full meal, you may need to increase your calories, possibly from protein.

Consider a ketogenic diet

While ghrelin increases after typical weight loss from calorie restriction, studies have shown that this increase is mitigated if the weight loss is a product of a ketogenic diet (29). It is my opinion that anyone attempting to follow a keto diet should do so under the instruction of a well-trained dietician or physician, as this diet can have negative health outcomes if not executed properly.

Avoid highly processed foods

You know, those foods that you can’t have just one of? Potato chips, pastries, soda, rolls, ice cream, French fries…foods that are high in calories and low in nutrients. Typically, when we consume a meal, our digestive system sends signals to our brain, indicating that it’s time to stop eating. However, research indicates that this feedback system doesn't function as effectively after a heavily processed meal.

As mentioned above, ghrelin will sufficiently reduce after a meal containing protein and healthy fats (and vegetables, always vegetables).

Increase muscle mass

If low body fat increases ghrelin, are low body fat individuals destined to be hungry all the time? Not if they have adequate muscle tone! Higher amounts of muscle has been associated with lower levels of ghrelin (6). This is possibly due to the fact that, while not an ideal fuel source, muscle can be used for fuel in a starvation situation and the body may panic less if it knows it has a backup.

Enjoy high intensity workouts

Researchers have discovered that ghrelin increases after long form cardio like walking, jogging, or bicycling, encouraging you to hammer a large meal when you’re done. Alternatively, ghrelin decreases after high intensity interval training (HIIT) (30). So while you are burning calories and increasing muscle mass, you are also decreasing appetite. Another study demonstrated how ghrelin was reduced up to 48 hours post workout (31).

Exercise has been shown to have an even greater effect on appetite, insulin sensitivity, and glucose tolerance when performed in the morning on an empty stomach as opposed to the afternoon. It is important to note though that there's more to consider than just ghrelin secretion when choosing when to exercise. Listen to your body, and most importantly, get moving whenever and however you can (32,33)!

Get enough sleep

Lack of sleep has been linked to weight gain for a myriad of reasons, and increased ghrelin levels is yet another (34,35). Just one night of inadequate sleep is enough to increase ghrelin secretion, and therefor hunger, throughout the day, regardless of other factors (36). And if that’s not enough, lack of sleep negatively affects just about every other hormone as well.

It is imperative to get at least 7 hours of sleep each night. Many people may need more.

Practice Stress Management

Not only does increased stress affect fat storage due to its influence on cortisol, it can encourage overeating by increasing ghrelin. This may make weight loss difficult, and weight gain post-diet more likely. A study published in Obesity Reviews concluded that “Behavioral interventions could offer a practical, cost-effective method for reducing or stabilizing ghrelin levels after initial weight loss to improve weight loss maintenance.” (37)

While it is worthwhile to remove as many stressors as possible, it is more likely you will need to manage the stress you can’t get rid of. This looks different for everyone but consider exercising, reading, spending time in nature, hanging out with friends, meditation, journaling, yoga, or anything else that brings you joy.

Conclusion

Ghrelin is a hormone that increases hunger when the stomach is empty. There is an inverse relation between ghrelin and body fat percentage - the more fat a person loses, the more ghrelin is secreted, increasing hunger both during a diet and even for weeks after. What's more, ghrelin production increases in times of stress, ie: a restrictive diet. It is also linked to the reward center of the brain, giving you a hit of pleasure when eating. All these factors play a part in the post-diet weight rebound that plagues the majority of those who have experienced weight loss.

It is important to recognize that the causes of obesity and weight gain are a lot more nuanced than poor diet and lack of exercise. Scientists continue to make incredible discoveries regarding the hormonal and genetic factors that contribute to a person's propensity for weight gain and excess weight balance.

If you are eating a balanced, whole foods diet, moving your body, getting adequate sleep, and moderating stress, yet are struggling to achieve a healthy weight, there may be more going on that should be addressed.