Hormones are chemicals that help your organs and systems communicate with one another. Without the influence of Hormones, humans and other complex life forms simply wouldn't exist. These tiny molecules are that important! Hunger seems like a simple concept at first glance—you need food to live, and your body tells you when it requires more calories. It seems so simple!
Upon further consideration, however, hunger is the result of a complex symphony of hormones that all work together to direct your actions to meet your needs. The adrenal glands, parathyroid, thyroid, and pituitary are all centers of hormone production that are involved in the physiological processes behind hunger and satiety, along with the digestive organs themselves. Let's talk about how hormones are involved in hunger.
Hormones Signal Both Hunger and Fullness
Hormones are deeply involved in all of the processes which influence our eating patterns. Some encourage us to eat, others tell us when to stop. Hormone Imbalance can lead to both overeating and insufficient intake, along with increased body fat or weight loss. Signals which control eating patterns are modulated by both the nervous system and the endocrine system, by both electrical signals and hormones.
The following hormones are all important to hunger response:
- Ghrelin is the hormone that's most widely known of the hormones associated with hunger—in fact, it's frequently referred to as The Hunger Hormone. It activates feelings of hunger by stimulating the hypothalamus, which is considered the control center of the brain and body. Ghrelin also plays a role in glucose metabolism, the circadian rhythm, and other functions.
- Motilin is secreted by the small intestine and leads to contractions of the intestinal muscles which are interpreted as hunger by the brain. This is one of the reasons that your stomach growls and rumbles when hungry.
- Neuropeptide Y (NPY) is controlled by leptin (the satiety hormone) and ghrelin. NPY is a short-chain hormone which encourages you to start eating. Its influence wanes as your intake increases.
- Agouti-related protein (AgRp) precedes the release of NPY. AgRp is released in response to Ghrelin activity and encourages the hunt for food. As feeding begins, AgRp levels decline sharply and NPY encourages continued eating.
The following hormones are related to fullness and slow down caloric intake:
- Cholecystokinin (CCK) is one of the hormones which stimulate the feeling of satiety. Protein and fat activate the release of CCK, but not carbohydrates. This is the main reason why fat and protein fill you up more quickly than starches and sugars. CCK also triggers gallbladder activity to process nutrients.
- Glucagon-like peptide-1 (GLP-1) is a hormone secreted by the intestines when you eat. GLP-1 tells your brain to slow down eating and feel more full. It also inhibits the emptying of the stomach, allowing your body to process food more efficiently.
- Peptide YY is another intestinal hormone that controls hunger. It works by reducing appetite. It also slows down the rate by which the digestive tract processes food.
- Leptin is a very notable digestive hormone. Unlike the hormones listed above, Leptin is produced primarily by adipose cells (fat). It's released to signal to the brain that fat cells have accepted sufficient energy from diet, and that it's time to stop eating. Leptin affects the activity of several other hormones directly, stimulating other hormones associated with satiety and suppressing AgRp and NPY.
- Insulin is responsible for regulating glucose and sustaining healthy energy levels. Insulin transports energy from the food that we eat for storage. Insulin production increases directly after eating, and as needs are met, Insulin signals the brain to eat less.
- Obestatin is believed to act counter to Ghrelin, suppressing hunger. It's understood to be important for digestion, but its full effects are not yet fully understood.
How HGH and Testosterone Relate to Digestion and Body Fat
Each of these hormones plays a critical role in the Hormone Cascade associated with digestion. Testosterone and Human Growth Hormone also interact with the digestive system. Human Growth Hormone acts in party with Insulin to meet the body's energy needs. HGH Levels increase as hunger-inducing hormone levels increase. HGH frees energy from fat cells for use by the body during lean times. Growth Hormone is also produced during period of high exertion, supplementing calories from diet.