Researchers at McGill University in Montreal have discovered that ghrelin, the “hunger hormone” known to stimulate appetite when you’re hungry or in need of calories, also makes you want to eat just because the food in front of you looks especially good.

Ghrelin is secreted by your stomach and, from there, sends a message to receptors in your brain, telling them to be more receptive to food’s visual cues. Your brain responds by shooting back a reply to your belly saying, “Hey, that looks good—let’s eat it!” For many people, hungry or not, that message is just too hard to resist.

Ghrelin targets the same “reward center” of the brain as drugs like nicotine, ethanol, and cocaine, a fact which may someday help explain why some foods have addictive potential. Everyone produces ghrelin, but leaner people produce more. People with anorexia, loss of appetite due to physical illness, or who are fasting or losing weight by dieting, have especially high levels of ghrelin circulating in their bloodstreams. That makes sense, because these are conditions under which your body, fearing starvation and armed with natural survival tools, wants you to eat. People who are obese and those who have had gastric by-pass surgery are found to have lower circulating levels of ghrelin.

Ghrelin’s real job, as scientists understand it, is to work with other hormones to correct appetite and energy imbalances, and help you maintain a consistent weight. Researchers believe that ghrelin also suppresses your body’s use of its own fat for energy. If you produce too much or too little ghrelin, however, these jobs can’t be done properly.

When there is an excess of ghrelin, or when circumstances occur that are known to affect normal hormonal action (such as lack of sleep), everyone—lean or obese—ends up eating more. If the release of ghrelin also makes food appear more desirable, that may help explain why there’s always room for dessert. And why your body always seems to work against you when you’re trying to lose weight.

By the way, in the study showing that grehlin stimulates a response to the mere sight of food, the participants weren’t even looking at real food. They were looking at pictures of food. The implications of this research may reach well beyond the normal urge to indulge in a sweet treat to illustrate the true impact of fast food advertising and accessibility on the weight-related health problems that continue to plague this country.

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