Scientists may have found the difference between picky eaters and those who just can't pass up seconds, thirds, and fourths--even when they're full. The answer lies in the appetite hormone leptin.
Leptin, an appetite suppressor, regulates eating by reducing a person's feeling of hunger when they're full. Interestingly, appetite has a strong effect on an area of the brain called the ventral striatum that has been linked to rewards and desires. In other words, satisfying a food craving can also be emotionally satisfying.
For many people, leptin works just as it should, telling us when we've had enough by making that last piece of chocolate cake look not so good when we've already stuffed ourselves. For some people with a rare congenital leptin deficiency, however, food stimulates that reward center of the brain even when they're not hungry. These people, scientists have found, don't have enough leptin to suppress their appetites, and are usually overweight.
The researchers from the University of Cambridge found that giving additional leptin hormone to people with leptin deficiency increased their feeling of fullness, and decreased their appetite. Obesity and being overweight may, in fact, be caused partially by physiological factors, and not just the rate of one's metabolism.
According to the study published in the journal Science, tests showed that leptin treatments did indeed work. Before leptin doses, the reward centers of subjects' brains lit up in response to images of food even when they were full; after leptin treatment, the reward centers only showed activity in response to food images when the subjects were actually hungry.
Hopefully, people who suffer from obesity who just can't seem to stick to a diet may be able to lead healthier lives with the help of a natural hormone--without the traditional idea of dieting.