An old proverb says "To a hungry man, there is no bad bread." That's because a particular stomach hormone named ghrelin is a key player in appetite and food consumption. This is according to Dr. Alain Dagher of the Montreal Neurological Institute.

In a study, Dagher and co. administered doses of ghrelin to participants while the latter were undergoing functional magnetic resonance imaging. The scientists then showed participants images of food and scenery (as a control) before and after the administration of the hormone. The participants also answered questions about mood and appetite.

Dagher discovered that ghrelin worked on the amygdala, insula, the orbitofrontal cortex and the striatum - regions of the brain known to be associated with reward and motivation. Apparently, these areas work together to assign incentive values to objects and actions. Incidentally, they are also the targets of drugs such as cocaine and nicotine.

Dr. Dagher summed up the results of the study this way:

Our study demonstrates that ghrelin actually activates certain regions of the brain to be more responsive to visual food cues, thereby enhancing the hedonic and incentive responses to food-related cues. Ghrelin is a hormone that triggers hunger, and is secreted by the stomach [when it is empty].

Dagher's may prove useful in treating and combating obesity. It may also help influence public policy toward such things as limiting or banning fast food from schools and junk food ads aimed at children. Until then, try to avoid shopping for food on an empty stomach.