The reason why we can't stop eating after one chip or one fry is that the fats in chips and fries trigger a biological mechanism in the gut that prompt the wanton intake of fatty foods, scientists have found.
UC Irvine researchers Daniele Piomelli, Nicholas DiPatrizio and colleagues found that when rats tasted something fatty, cells in their upper gut started producing natural marijuana-like chemicals in the body called endocannabinoids.
Sugars and proteins, the researchers noted, did not have this effect.
The process starts on the tongue, where fats in food generate a signal that travels first to the brain and then through a nerve bundle called the vagus to the intestines.
There, the signal stimulates the production of endocannabinoids, which initiates a surge in cell signaling that prompts the wanton intake of fatty foods, Piomelli said, probably by initiating the release of digestive chemicals linked to hunger and satiety that compel us to eat more.
"This is the first demonstration that endocannabinoid signaling in the gut plays an important role in regulating fat intake," added the Louise Turner Arnold Chair in the Neurosciences and professor of pharmacology.
The study has been published in the online edition of Proceedings of the National Academy of Sciences.