A hormone deficiency in the brain may be a reason why we eat even if we’re not hungry.
Mice who didn’t have enough of the hormone (called GLP-1) overate and consumed more high-fat food. When researchers at Rutgers activated the hormone in the brains of the mice, they were less interested in the fatty foods.
GLP-1 peptides are small sequences of amino acids that have many functions, including how our bodies regulate eating behaviors. They are secreted from cells in both the small intestine and the brain and are supposed to let our brain know when we are satisfied and should put down the fork.
It’s not been clear how the GLP-1 released in the brain contributes to appetite regulation. Although this is not the only reason why people overeat, scientists say, the study provides new evidence that targeting neurons in the mesolimbic dopamine system—a reward circuit in the brain—rather than targeting the whole body might be a better way to control overeating and obesity with fewer side effects.
In the study, the authors found that activating the GLP-1 hormone in the mesolimbic system hindered communication between neurons and controlled reward behaviors, including eating. The result was that mice consumed less food altogether and, more important, lost the preference for high-fat food.
“These are the same areas of the brain that control other addictive behaviors like drug and alcohol abuse and nicotine addiction,” says Zhiping Pang, an assistant professor at Rutgers Robert Wood Johnson Medical School and senior author of the study published in Cell Reports.
Pang says why we eat, how much we eat, and when we stop eating are behaviors controlled by the central nervous system, which enables the body to respond to its environment. This is why it is important to understand the motivation behind hedonic hunger—the drive to eat for pleasure instead of to gain energy.
Effective therapies for treating obesity are very limited. A drug that mimics the GLP-1 hormone—used first to improve glucose tolerance for those with type 2 diabetes—and recently approved by the US Food and Drug Administration is now being used as a treatment for obesity. The injectable medication that targets the whole body, however, can possibly cause serious side effects, including pancreatitis, gallbladder disease, and kidney problems.
“Overeating, which causes obesity, can be considered a food addiction, a neuropsychiatric disorder,” Pang says. “By finding out how the central nervous system regulates food intake behavior via GLP-1 signaling, we may be able to provide more targeted therapy with fewer side effects.”