Why Do We Feel Hungry? | What Happens in Your Body When You're Hungry? | Ghrelin Hormone | Dr Binocs

Hunger can also originate in the blood. When essential nutrients like glucose, amino acids, or fatty acids are low, blood vessels signal the brain's hunger center, indicating a 'fuel shortage' even if the stomach feels full.

The video starts by questioning if hunger is solely due to an empty stomach, introducing the idea that it's a more complex 'whole body message' involving hormones and nerves communicating with the brain.

A few hours after eating, the body initiates a 'cleanup' process called the migrating motor complex (MMC), which flushes leftovers from the intestines. This process takes about two hours, and the release of the hormone motilin causes the familiar stomach rumble, scientifically known as borborygmus.

Ghrelin, a hormone produced in the stomach, acts as the body's 'hunger text message.' It travels to the brain's hypothalamus, specifically activating AGRP neurons, which are key in signaling hunger and prompting a desire to eat.

The video explains that one can feel hungry even when full, due to 'brain hunger' or cravings triggered by sights, smells, or thoughts of food. This can increase ghrelin levels, making the brain desire snacks even without a physiological need.

The vagus nerve provides updates on stomach fullness and nutrient levels, while low leptin (a hormone that signals fullness) can also contribute to hunger. Low blood sugar triggers a 'panic switch,' releasing stress hormones like cortisol and adrenaline, leading to moodiness or 'hangry' feelings.

Cravings for junk food are explained by their ability to release feel-good chemicals in the brain, offering a 'tiny high.' This reward system, once crucial for ancestors surviving famines, now contributes to issues like obesity.

The video concludes by encouraging viewers to distinguish between true physiological hunger for fuel and 'brain hunger' for fun, emphasizing the importance of listening wisely to the body's messages.

As a trivia, the video mentions that sickness can suppress appetite. The immune system releases cytokines, which reduce hunger to allow the body to focus its energy on fighting infection.