It's late at night and you really just want another slice of that chocolate cake — even though you're not hungry.
A new study published this week in the journal Cell Reports suggests that overeating happens when people don't have enough of a hormone called glucagon-like peptide-1, or GLP-1. The chemical is secreted from cells in both the small intestine and the brain to let our brain know when we've had enough to eat.
The study, by a team of researchers from Rutgers University, looked at how levels of the hormone affected laboratory mice. When GLP-1 was reduced in the mice, they over-ate and consumed more high-fat food. When researchers enhanced the signal, they were able to block the mice's interest in fatty foods.
While it still needs to be established that the same effect happens in humans, there is already a drug on the market that scientists say mimics the hormone. Earlier this year, the Food and Drug Administration approved a Saxenda — a drug originally designed to improve glucose tolerance for diabetics — as a treatment for obesity.
The drug targets the whole body, which has side effects that can cause problems for the pancreas, gallbladder and kidney. The study offers new evidence for a different approach to affect only the neurons in the brain that are responsible for putting the fork down.
"If we knew exactly where the hormone is in the brain, we could target the disorder better," said Zhiping Pang, an author of the study and a professor at Rutgers.
How our nervous system uses hormones to regulate how much we eat and when we stop is still not very well known. Pang said further research using human stem cells from people with eating disorders should give more insight into what is called hedonic hunger — the drive to eat for pleasure rather than to gain energy.
This is the same place in the brain that controls other addictive behaviors, like drug, alcohol and nicotine addiction. Pang said understanding this hormone could have broader implications for how the brain's chemistry influences the other motivational behaviors.
The research team said hormone deficiencies are not be the only factors contributing to overeating. Doctors also point to social and cultural pressures, as well as psychological causes such as depression.
More than one-third of U.S. adults — about 78.6 million people — are obese, according to the Centers for Disease Control and Prevention. The condition is linked to heart disease, strokes, diabetes and some cancers, causing an estimated medical cost of $150 billion every year.