What Drives Us to Eat? - Influence of Hunger & Appetite

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  • 0:01 Appetite & Hunger
  • 1:18 The Physiology of Appetite
  • 2:14 Hormones & Appetite
  • 3:46 The Nervous System & Appetite
  • 4:44 External Cues & Appetite
  • 5:26 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Appetite and hunger involve the interaction of your brain and hormones, and they are further influenced by external cues. Learn about the role the hypothalamus, vagus nerve, leptin, ghrelin and neuropeptide Y play in driving your desire to eat.

Appetite and Hunger

Appetite, or your desire for food, is a constant in life. This is a good thing because food provides the body with nutrients needed to keep you going throughout your day. You literally eat to live, yet having too much desire to eat can make you feel as if you are living to eat and lead to unwanted pounds and health problems. All of us have been drawn in by the tempting smell of fresh baked cookies straight out of the oven, yet the true driving force behind what makes you want to eat is a fairly complex interaction between your body and your brain.

You take notice to your appetite when you experience hunger, which is the uncomfortable feeling caused by a need for food. We have all experienced hunger; it only takes a few hours of not eating to trigger the sensation. This sensation is called hunger pangs, which is the discomfort felt in the abdominal region associated with contractions of the empty stomach.

Appetite and hunger are sometimes used interchangeably, yet they are not the same thing. You can have an appetite without being hungry. If you ever wanted to eat a piece of chocolate cake after a big meal, even though your body didn't need the calories, then you know what I am talking about.

The Physiology of Appetite

To best understand what stimulates appetite and hunger, it is good to build our basic understanding of how the body handles and stores nutrients. The body's main source of fuel is glucose, followed by fatty acids or lipids. When you eat carbohydrates and fats, these fuels are absorbed into your bloodstream to be used immediately for energy or to be stored in body cells for later use. When your body's storehouse of nutrients is depleted, appetite and hunger are initiated.

Knowing this gives us the big picture, yet at the same time oversimplifies matters. After all, regulating appetite is not as simple as filling your car's gas tank and driving for 200 miles before needing the next fill-up. Instead, appetite and hunger are complex processes that involve the interaction of your brain and hormones, and they are further influenced by your habits, external cues and your emotions.

Hormone and Appetite

Let's start with a look at how hormones influence your desire to eat. Hormones are the emergency responders of the body and are constantly on alert ready to be released or suppressed in order to maintain homeostasis. The digestion and storage of nutrients involves the interplay of many hormones, but when looking at the hunger hormones, we can put most of our focus on just two.

The first is leptin, which is a hormone secreted by your fat cells that acts as an appetite suppressant. Leptin levels peak when you fill up on food. So, when you eat a lot, your appetite goes away. If you ever said, 'I am so full I couldn't eat another bite,' then in that moment, your body was flooded with leptin. It might help you to recall the action of this hormone by remembering that leptin lowers hunger.

Now that you are full, you will probably wait a few hours before eating again, and this brings the second hunger hormone into the game called ghrelin. Ghrelin is a hormone secreted by the stomach that acts as an appetite stimulator. If you ever said, 'I am so hungry that my stomach is growling,' then your body was flooded with ghrelin. So if your stomach is growling, then it is producing ghrelin.

Ghrelin communicates with your brain and triggers the release of an additional hormone called neuropeptide Y, which is a hormone secreted by the hypothalamus that stimulates hunger.

The Nervous System and Appetite

Your hypothalamus is the part of your brain that regulates appetite and hunger. In fact, your hypothalamus stays pretty busy with this function, taking in data from different sources. Tucked up inside your brain, this collection of nervous tissue receives inputs from the vagus nerve, which is actually a cranial nerve that sends signals from the gastrointestinal tract to the brain. The signals are reports on how distended your stomach is - in other words, how full you are. If you stomach is filled up with food, then hunger is suppressed.

The hypothalamus also receives input about the levels of hunger hormones that we discussed earlier and adjusts your appetite accordingly. In addition, the hypothalamus monitors the amount of lipids and sugars in your blood. If you haven't eaten in awhile, these levels begin to drop, and it's time for more fuel, so your hypothalamus releases the hormone neuropeptide Y to drive you to eat.

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