Researchers at the University of California have discovered that it's not just the carbohydrates that give you cravings for potato chips.

UC Irvine researchers Daniele Piomelli, Nicholas DiPatrizio and colleagues found that fats in these foods make them nearly irresistible and trigger a surprising biological mechanism that likely drives our gluttonous behavior. The apparent culprit? Natural marijuana-like chemicals in the body called endocannabinoids.

In their study, the Piomelli team discovered that when rats tasted something fatty, cells in their upper gut started producing 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.