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Anyone who has tried to lose weight has likely faced the same puzzle: Why does your appetite go up as your weight goes down? Why do you feel hungry right after eating some foods and not others? And why is it so easy to regain weight after losing it? The answer lies in hunger hormones like ghrelin.
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What is ghrelin?
Ghrelin is a hormone made in the stomach, brain, intestines, and pancreas. It helps regulate your appetite and metabolism. Since it makes you feel hungry, it’s often called the “hunger hormone.” But there are many other effects of ghrelin, such as (Müller, 2015; Mao, 2014):
- It helps move food through your digestive system.
- It stimulates your stomach to produce acid.
- It helps your brain make certain hormones.
- It may even protect you against heart disease (cardiovascular disease).
Why is ghrelin called the hunger hormone?
Ghrelin helps control how many calories you take in and how many of those you store as fuel for later, ultimately contributing to your energy balance. Ghrelin levels increase right before a meal to let your body know it’s time to chow down and take in the calories you need.
The hormone then sends signals to a part of your brain called the hypothalamus (aka the “fullness center” or “satiety center”). The signals make you hungry, so you eat more calories and store more fat (adipose tissue) (Young, 2021). After you’ve eaten, your levels of ghrelin decrease.
Not all foods are created equal in ghrelin’s proverbial eyes, though. Foods high in protein keep ghrelin levels stable, which is why people feel satisfied for longer after a high-protein meal. Carbohydrates and fat, on the other hand, cause ghrelin levels to drop rapidly, making you feel satisfied quickly. But that rapid drop is typically followed by an abrupt rebound so you get hungry again soon after eating fat and carbohydrates (Koliaki, 2010). Most of us have experienced that after throwing back several slices of pizza and still being able to go for more.
Ghrelin and leptin: how they relate
Ghrelin works hand in hand with a hormone called leptin to regulate your appetite. Leptin, the “fullness hormone,” signals your brain to make you feel satisfied when you’ve eaten enough. When you don’t eat enough, your leptin level decreases while your ghrelin levels go up, telling you that it’s time to eat more (Klok, 2007). Together, leptin and ghrelin levels strongly influence your appetite and weight.
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Ghrelin and obesity
Since ghrelin is closely tied to appetite and weight, it’s a key player in developing overweight and obesity.
As we’ve seen, ghrelin levels stimulate your appetite before you eat, then decrease after a meal. But in people with obesity, ghrelin levels remain high even after eating enough calories. These individuals will likely still feel hungry after eating, leading them to consume extra calories and potentially gain more weight (English, 2002).
Another phenomenon some people experience is when the receptor in the brain that processes ghrelin is too sensitive. In that case, your brain will tell you to eat more even when you don’t actually need more food (Wang, 2016). The opposite occurs in people with anorexia. The receptor isn’t sensitive enough—a condition called ghrelin resistance—so even though ghrelin tells the brain it’s time to eat, the brain doesn’t receive the signal properly (Schalla, 2018).
After losing weight, ghrelin may also make it challenging to keep weight off since ghrelin levels increase when people lose weight. So, you may follow a nutritious diet and exercise but still find that it’s a struggle to keep the weight off (Cummings, 2002).
Ghrelin and diabetes
People with type 2 diabetes usually benefit from reducing excess weight (if necessary). But people with diabetes and higher ghrelin levels also have a higher risk of gaining back the weight they lose (Thom, 2020).
People with type 2 diabetes experience high blood sugar (glucose) and insulin resistance, a condition in which the body doesn’t respond to the hormone that regulates blood sugar. Elevated ghrelin levels have been linked to increased insulin resistance, making blood sugar control even more challenging (Tong, 2016).
Can lowering ghrelin help you lose weight?
Ghrelin makes you feel hungry, and people with higher body weights usually have higher ghrelin levels (Makris, 2017). So does lowering your ghrelin level help you lose weight?
This seems to be the case in people who have bariatric surgery, which is a procedure done for weight loss. Ghrelin levels drop significantly after bariatric surgery, which may contribute to the weight loss people experience. How does it happen? The theory is that ghrelin is mainly produced in a part of the stomach called the fundus, which is removed during this procedure, meaning post-surgery, people have less of the hormone (Cummings, 2009).
Researchers are currently studying medications that lower ghrelin as possible treatments for obesity. There are no trials yet in humans, but the results in animal studies are encouraging (Schalla, 2018).
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How can you lower ghrelin?
There are currently no medications approved to lower ghrelin, but that doesn’t mean there’s nothing you can do in the meantime. There are many natural ways to help regulate ghrelin levels, including:
- Exercise: Getting regular exercise has many health benefits, and it seems that lowering ghrelin is one of them. Aerobic exercise may lower ghrelin levels and improve sensitivity to leptin, which can help reduce weight (Dorling, 2018; Peng, 2021).
- Eat more protein: Eating enough protein is part of a nutritious diet, and foods with protein may help regulate ghrelin levels so that you feel more satisfied after eating (Parvaresh Rizi, 2018).
- Eat less sugar: Fructose is a sugar found in additives like high-fructose corn syrup, used to flavor sweet snacks, sodas, sugary drinks, and sauces. A high-fructose diet may raise ghrelin levels and increase your appetite (Lowette, 2015). Eating less sugar also helps your body regulate insulin and glucagon levels, which also play an important role in how hungry you are.
- Get enough sleep: Sleep deprivation is linked to high ghrelin levels and weight gain, so getting adequate sleep may help control your ghrelin levels (Lin, 2020).
- Go slow and steady: Losing weight quickly may sound tempting, but you’ll achieve lower ghrelin levels through steady, sustainable weight loss, as opposed to extreme weight loss (Hooper, 2010).
- Reduce stress: Chronic stress can significantly elevate your ghrelin (Abizaid, 2018). Keeping your stress levels under control and taking care of your mental health can help balance your ghrelin levels.
- Cut back on cannabis: Marijuana (cannabis) is a well-known trigger for “the munchies.” This may be related to one of the main active components of cannabis, THC (tetrahydrocannabinol). THC can raise ghrelin levels and stimulate the reward pathways in your brain, making you seek foods that drop ghrelin quickly, like fats and carbohydrates (Farokhnia, 2020; Perello, 2015).
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Ghrelin is closely tied to your appetite and weight regulation. There are currently no medications available to regulate your ghrelin levels, but there are natural ways to improve them.
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