Photo: allanpat, sxu.hu

Hunger is a helpful little signal. It's the body's way of telling us when it needs food. Granted, we find all sorts of ways of short-circuiting that hunger signal. When we're bored or stressed, emotions can make us reach for food even when we don't need it, and if we don't slow down while eating, we can often overeat. So it would stand to reason that, if you ate slowly (giving your body time to feel full) and controlled emotional eating, you would never overeat, right? For some people, it's not as simple as that.

Hyperphagia happens when a person's hunger rages out of control and the body doesn't indicate fullness as it normally should. Associated with rare conditions such as Prader-Willi Syndrome (PWS), hyperphagia can cause a person to overeat excessively -- even sneaking or stealing food in an attempt to satisfy their unstoppable hunger. About 4,500 Americans are diagnosed with PWS, but experts believe that undiagnosed cases would raise the total to nearly 30,000.

Ghrelin, a natural hormone that plays a role in hunger, has long been suspected as a culprit in hyperphagia. And scientists are continuing to study ghrelin and other possible factors behind hyperphagia. Detangling the complicated mystery that is PWS and hyperphagia could have a positive impact on the greater population as well. While true hyperphagia is relatively rare, understanding the medical causes of the problem could also help researchers in the study of obesity.