The Hormones That Regulate Hunger and Digestion

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Before your body can benefit from any nutrients you consume, your gastrointestinal tract has to digest and absorb the foods you eat. But before you eat, it helps to feel hungry.

Hunger isn't the same as appetite. Appetite is one reason why you can eat so much when you're not hungry. Hunger is a physical reaction caused by hormonal and chemical changes in your body when you need more food.

Appetite is more psychological in nature and is sometimes a learned response to certain foods. There are different hormones that regulate hunger, appetite, and digestion.

Hunger Hormones

Hunger is the feeling you get when your body needs food. When you've had enough to eat, you shouldn't feel hungry anymore. That's because a variety of hormones regulate hunger.

Leptin

Leptin is a hormone secreted by adipose tissue (fat) into your bloodstream. The more fat on your body the higher your blood levels of leptin. Your leptin level also increases with food intake and is higher in females than males, but overall, it gets lower as you get older. Increased leptin levels trigger the hypothalamus to reduce hunger.

Ghrelin

Ghrelin is a hormone produced by the stomach and small intestine when your stomach is empty. Like leptin, it also works with the hypothalamus, but instead of suppressing hunger, it increases hunger.

Adiponectin

Adiponectin is a hormone secreted by fat cells in your body. But as your level of body fat goes down, this hormone goes up and vice versa; when you gain fat, your adiponectin levels go down.

Cholecystokinin

Cholecystokinin is a hormone produced in the small intestine during and after a meal. It triggers the release of bile and digestive enzymes into the small intestine, and it suppresses hunger and makes you feel full.

Peptide YY

Made by both the large and small intestine after a meal, this hormone suppresses your appetite for about 12 hours after you eat.

Insulin

The pancreas produces this hormone. It's best known for regulating blood sugar levels. It also suppresses hunger.

Glucocorticoids

These hormones are made by your adrenal glands, and their primary function is to regulate inflammation and other processes, but they also have an impact on hunger. A cortisol deficiency reduces appetite, but excessive amounts of glucocorticoids increase hunger.

Digestion Hormones

Now that you're hungry, it's time to eat. Digestion is coordinated and regulated by several hormones.

Gastrin

Gastrin is a hormone released by the stomach and the small intestine when you eat. Gastrin stimulates the release of hydrochloric acid and pepsinogen in the stomach, and it speeds up digestion. Also, gastrin stimulates glucagon, a hormone that works with insulin to regulate blood sugar.

Secretin

Secretin is a hormone made by the small intestine and secreted into the bloodstream when the acidic chyme from the stomach enters the small intestine. Secretin stimulates the pancreas to release bicarbonate-rich digestive juices into the small intestine.

The bicarbonate neutralizes the acidity of the chyme. Secretin acts on the stomach to trigger production of pepsinogen to help break down proteins, and it might also slow down the digestive process, at least in the area of the stomach and first part of the small intestine.

Cholecystokinin (CCK)

Your small intestine makes and releases CCK into your bloodstream. It's essential for fat digestion because it stimulates the gallbladder to release bile into the small intestine. It also triggers the pancreas to release its various digestive enzymes into the small intestine so they can break down fats, carbohydrates, and proteins.

Motilin

Motilin is another hormone made by the small intestine. Motilin speeds up activity in the stomach and small intestine. It also stimulates the stomach and pancreas to release various secretions and causes the gallbladder to contract.

Glucose-dependent insulinotropic peptide (GIP)

This hormone is made by the small intestine. It stimulates the pancreas to release insulin and slows down digestive activity in the stomach. This hormone is sometimes called gastric inhibitory peptide.

Peptide YY and enterogastrone

These are two more hormones released by the small intestine that slow digestion down and decrease the production of digestive secretions.

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Additional Reading
  • Gropper SS, Smith JL, Groff JL. "Advanced Nutrition and Human Metabolism." Sixth Edition. Belmont, CA. Wadsworth Publishing Company, 2013.
  • Klok MD, Jakobsdottir S, Drent ML. "The Role of Leptin and Ghrelin in the Regulation of Food Intake and Body Weight in Humans: a Review." Obes Rev. 2007 Jan;8(1):21-34.
  • Smolin LA, Grosvenor, MB. "Nutrition: Science and Applications." Third Edition. Wiley Publishing Company, 2013.
  • United States Department of Health and Human Services, National Digestive Diseases Information Clearinghouse (NDDIC). "Your Digestive System and How It Works."