If you find yourself downing an extra piece of chocolate fudge cake even though you're not hungry, it may not be your lack of willpower but a hormone deficiency that is causing you to overeat, a new study suggests.

When a hormone known as peptide-1 (GLP-1) was reduced in the central nervous system in mice, it triggered them to eat high-fat food even after they had already been well fed.

GLP-1 peptides are small sequences of amino acids that have many functions, including regulating eating behaviors in both mice and humans. They are produced by cells in the small intestine and the brain, and let our brain know when we have eaten enough.

Researchers at the Rutgers Robert Wood Johnson Medical School discovered that when GLP-1 deficiency was induced, the mice ate beyond their need for calories and showed an increased preference for high-fat food. When they enhanced the hormone’s signaling, the mice ate less.

GLP-1 also controls addictive behaviors such as drug, alcohol, and nicotine addiction, so the researchers are hoping their work will lead to further understanding on how the hormone may be manipulated to improve these behaviors.

A drug that mimics GLP-1 was recently approved by the U.S. Food and Drug Administration as an injectable treatment for obesity, but it is not in widespread use because of potentially serious side effects. Researchers are hoping the new study could lead to more targeted obesity treatment with fewer side effects.