Hunger and satiety may seem like straightforward sensations: You feel hungry when you haven’t eaten for several hours and then you feel full after you’ve consumed enough. But the reality is more complicated. Behind the scenes, a constellation of hormones works to regulate hunger, satiety, and fat storage in ways that influence your body weight and health.
“The body’s energy regulation system is very complicated,” says Caroline M. Apovian, an obesity medicine specialist and codirector of the Center for Weight Management and Wellness at Brigham and Women’s Hospital. Simply put, it’s the interplay between hormones in the gut and brain, especially in the hypothalamus, that regulate hunger and satiety. “These hormones work in a synergistic or counter-regulatory fashion to protect you from starving,” she explains. “The main effect is to protect your fat stores and keep your body weight as steady as possible.”
Indeed, this hunger-satiety regulatory system has an evolutionary basis, and it influences your metabolic rate, body weight setpoint (your predisposition to maintain a certain weight), and other factors that are critical for survival.
Some of these hormones are influenced by genetic factors, while others are affected by lifestyle, certain medical conditions, and/or changes in body weight or composition. Against this backdrop, various hormones influence the short-term regulation of food intake—primarily to prevent overeating at any given meal—while others focus on long-term regulation to maintain normal amounts of energy stores in the body, explains Lawrence Cheskin, a gastroenterologist and professor of nutrition and food studies at the George Mason University College of Public Health and coauthor of Weight Loss for Life.
Experts caution against focusing exclusively on any one of these hormones because they work together like instruments in an orchestra.
Here’s a closer look at seven of the major players for appetite regulation:
Leptin: Biologists used to think that fat tissue was inert, but now it’s considered an endocrine organ because it produces hormones, including leptin. Fat cells throughout the body secrete leptin to signal satiation and reduce appetite and food consumption. “The discovery of leptin in 1994 started the boom in research in this area—before that, we didn’t realize how the fat depots [in the body] communicate with the brain,” Apovian says.
However, people who are obese tend to have higher leptin levels because they have greater body fat or because their bodies are resistant to the hormone. By contrast, if you cut calories and lose body fat, your leptin levels will decrease, Apovian notes. “Leptin is trying to protect against starvation and loss of fat mass—it’s related to the setpoint of body weight.”
Ghrelin: Often called the “hunger hormone,” ghrelin is produced by the stomach. “Levels of ghrelin are high just before eating, then they fall after a meal,” Cheskin says.
If you cut calories to try to lose weight, your baseline levels of ghrelin will increase. “This makes it harder to lose weight because your hunger is stimulated more than usual,” says Marcio Griebeler, an obesity specialist, endocrinologist, and director of the Obesity Center with the Cleveland Clinic’s Endocrinology & Metabolism Institute. A study in a 2017 issue of the journal Obesity found that people with higher baseline levels of ghrelin had more food cravings, especially for high-fat or sweet foods and greater weight gain over a six-month period.
Cholecystokinin (CCK): A satiety hormone that’s produced in the gut after you’ve eaten, CCK helps you feel full, Apovian notes. It also enhances digestion by slowing down the transit of food from the stomach, thereby boosting feelings of fullness and increasing the release of fluids and enzymes from the pancreas to metabolize fats, proteins, and carbohydrates. And CCK may affect the appetite centers in the brain in ways that reduce appetite and subsequent food intake, though this mechanism isn’t fully understood.
Insulin: Insulin is secreted by the beta cells in the pancreas after an increase in blood glucose (sugar) in the bloodstream. “As you eat carbohydrates, you start releasing more insulin, which puts more glucose back into cells for energy,” Griebeler says. Insulin also promotes satiety, Apovian says. Insulin resistance occurs when the body ignores or doesn’t respond properly to insulin; this can be related to obesity, lack of physical activity, or eating foods rich in simple carbohydrates, Griebeler adds.
Cortisol: Best known as a stress hormone because it’s produced in larger amounts when the body’s stress response kicks into high gear, cortisol actually has many different functions— including regulating metabolism. Higher baseline levels of cortisol are associated with insulin resistance and greater fat storage, Griebeler says. With chronic stress, “a surge of cortisol is associated with increased appetite, especially for sweet, salty, or fatty foods, and an increase in blood sugar and insulin levels,” notes Frances Lee, a family nurse practitioner specializing in obesity medicine at RUSH University Medical Center in Chicago. In fact, a study in a 2022 issue of the journal NeuroImage: Clinical found that more cortisol induces hunger and decreased blood flow in brain regions that regulate food intake.
Glucagon-like peptide-1 (GLP-1, for short): Released in the gut after eating, GLP-1 interacts with receptors in the brain to trigger satiety. It also slows digestion and the movement of food through the gastrointestinal tract, “which causes you to feel full for longer so you tend to eat less overall,” explains Griebeler.
Glucose-dependent insulinotropic polypeptide (GIP): This hormone is produced by the small intestine after you have eaten and increases insulin levels which stimulate the production of glycogen and fatty acids that inhibit the breakdown of fat. GIP is a relative new kid on the block, so there are still many unanswered questions about it.
The new anti-obesity interventions
One of the most exciting developments related to hunger hormones has been the development of new medications that boost the effects of the hormones GLP-1 and GIP to treat obesity and diabetes, Griebeler says.
These include a drug called semaglutide, which the Food and Drug Administration approved in 2021 under the brand name Wegovy. It’s a weekly injection for people with obesity or overweight people who have at least one weight-related condition (such as high blood pressure); in 2017, the same drug was approved as Ozempic, also as an injection, for people with type 2 diabetes. In 2022, the FDA approved an injectable drug called tirzepatide (Mounjaro) for adults with type 2 diabetes.
These drugs are proving to be game-changers, decreasing people’s appetites and regulating their blood sugar, Cheskin says. They’re also helping people who are overweight or obese lose considerable amounts of weight, but they’re meant to be used with dietary changes and exercise. “You can’t rely solely on medications—they are not the whole solution,” Griebeler says.
Lifestyle modifications need to be part of the picture, too, whether or not you’re taking one of these drugs.
Sticking with a healthy eating plan
That means consuming minimally processed foods and plenty of whole grains, fruits and vegetables, and lean proteins. With this approach, “you will most likely get a balance of macronutrients so you will feel full with an appropriate level of calories,” Apovian says.
Keep in mind: “It’s not just how much you eat—it’s also how quickly you eat, how often in a day you eat, and the food components that influence eating behavior,” explains Cheskin, who recommends eating small meals and snacks at three-hour intervals to gain greater stability of these hormones.
Getting plenty of sleep: Sleeping well is essential for regulating several hunger hormones. “If you don’t sleep well, you have higher levels of cortisol and ghrelin and lower levels of leptin,” Griebeler says. In fact, a study in the March 2023 issue of the journal Obesity found that women had even more pronounced decreases in the satiety hormone leptin after a night of sleep deprivation than men did, and people who were obese had a greater increase in ghrelin (the hunger hormone) after the sleep loss.
Exercising regularly: Research has found that aerobic exercise can temporarily suppress hunger, blood levels of ghrelin, and increase levels of GLP-1 in people. And some studies suggest that higher intensity exercise has an even greater effect in suppressing ghrelin in healthy people. Exercise regularly and you’ll put these hormonal changes on your side—and help insulin work better in your body, Lee says.
Finding ways to manage stress: It’s basically impossible to avoid stress but if you take steps to manage it, you’ll do yourself a big favor when it comes to your hunger hormones and your ability to regulate your appetite.
Research has found that while acute stress results in eating less, chronic stress causes higher cortisol levels that can lead to eating more, especially high-calorie palatable foods.
To relieve stress and lower cortisol levels, your best bet is to regularly engage in deep breathing or exercise, Lee says. A study in a 2022 issue of Behavioral Sciences found that simply doing a 12-minute session involving respiratory biofeedback (using specific breathing skills for relaxation) leads to a significant decrease in salivary cortisol concentrations.
