The premise that hunger makes food look more appealing is a widely held belief. Prior research studies have suggested that the hunger hormone ghrelin, which the body produces when it's hungry, might act on the brain to trigger this behavior.
New suggests that ghrelin might also work in the brain to make some people keep eating "pleasurable" foods when they're already full. Scientists previously have linked increased levels of ghrelin to intensifying the rewarding or pleasurable feelings that can be gotten
Researchers observed how long mice would continue to poke their noses into a hole in order to receive a pellet of high-fat food. Animals that didn't receive ghrelin gave up much sooner than the ones that did receive ghrelin. Humans and mice share the same type of brain-cell connections and hormones, as well as similar architectures in the "pleasure centers" of the brain.