Why We Keep Eating When Full

Posted by Admin on September 28, 2010
Why do we keep eating pleasurable foods when full? The answer may seem obvious, but a recent article published in Biological Psychiatry has a scientific answer in the hunger hormone ghrelin.

Researchers at UT Southwestern Medical Center wanted to know whether ghrelin, which stimulates us to eat when we are hungy, also triggers the brain to eat pleasurable food even after being full. Co-senior author of the study, Dr. Jeffrey Zigman claims, “What we show is that there may be situations where we are driven to seek out and eat very rewarding foods, even if we’re full, for no other reason than our brain teslls us to.”

Previous research has found that increased levels of ghrelin intensified pleasurable feelings a person could achieve from alcohol or cocaine. These feelings also function as reward motivators: “They give us sensory pleasure, and they motivate us to obtain them. They also help us reorganize our memory so we remember how to get them.”
Lead author of the study, Dr. Mario Perello, conjectures that an increase in ghrelin may explain why a person may eagerly eat that rich, high calorie dessert even after eating a hearty meal that is completely filling.

The study authors examined mice that were already well-fed and given a choice – to visit a room where they had previously tasted high-fat food versus one that offered the standard bland mouse vitals. When the researchers administered the ghrelin hormone to mice, they strongly perferred the room where they had enjoyed the high-fat food. The mice without the pleasure-seeking hormone showed no noticeable preference.

Dr. Perello said, "We think the ghrelin prompted the mice to pursue the high-fat chow because they remembered how much they enjoyed it. It didn't matter that the room was now empty; they still associated it with something pleasurable."

Ghrelin is normally secreted into the bloodstream upon fasting or caloric restriction. However, when the researchers blocked the natural secretion of the ghrelin the mice also spent less time in the high-fat bistro.

So does this mean anything for the human species and their fat-seeking habits?  The researchers thought so: They claimed, “Humans and mice share the same type of brain-cell connections and hormones, as well as similar architectures in the so-called "pleasure centers" of the brain. In addition, the behavior of the mice in this study is consistent with pleasure- or reward-seeking behavior seen in other animal studies of addiction”

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