Humans Eat Because of Hunger, Not for Nutritional Nourishment

Although the main function of eating is to fulfill our nutritional needs, a study conducted by the Beth Israel Deaconess Medical Center (BIDMC) in Boston has found that mere hunger is the real reason humans seek food.

There's a large prevalence of abnormal hunger, such as overeating and cravings for unhealthy foods, which can lead to obesity and eating disorders. This abnormal hunger shows that people don't necessarily have nutritional nourishment in mind when eating.

Over the past 20 years, BIDMC neuroendocrinologist Bradford Lowell, MD, PhD, has been working to create a wiring diagram that helps regulate such intense motivational states in complex brain circuits. His discovery of Agouti-peptide (AgRP) expressing neurons were critical. This group of nerve cells in the brain's hypothalamus (as examined in mice) are activated by caloric deficiency, which cause an insatiable hunger. The researchers found that when they stimulated these neurons either naturally or artificially in the experimental mice, the rodents would eat uncontrollably and constantly search for food.

Lowell's study was published in the journal Nature this week and was funded by grants from the National Institutes of Health. He coauthored the study with researchers from BIDMC as well as colleagues from Harvard University and the University of Michigan.

The researchers wanted to understand how the brain controls hunger, and the role of Agouti-peptide expressing neurons may provde the answer. The AgRP neurons are activated by hunger-inducing neurons located in the paraventricular nucleus, which is a region of the brain associated with feelings of fullness. This finding helps provide further understanding into what propels appetite.

As noted before, Lowell has been manipulating brain circuits to see what causes different degrees of hunger. The brain region in question is described as "a dense and daunting tangle of circuits resembling a wildly colorful Jackson Pollack painting," in this EurekAlert! article. Currently, the researchers are continuing to maneuver through this brain region by manipulating different circuits to ultimately find out how the messages of hunger or fullness enter the region.

The study reveals more discoveries and insight in this article.