Addicted to Food? Oliver Grimm Abstract What drives people, against their better judgment, to eat more food than they need? Scientists look to the brain for answers Introduction Its been a long day, and you are still at the office. With your blood sugar plummeting, your brain starts to obsess: Where can I get some food? You gather your money and dash across the street to the fastfood place. But as you bite into the greasy burger, your conscience suddenly kicks in: What am I doing? ADDITIONAL IMAGES AND ILLUSTRATIONS o FAST FACTS Addiction and Obesity It is a common scenario for many of us. Hunger is a potent, if only temporary, condition that can overpower our very best nutritional intentions. In its absence, the brains cerebrumgoverning conscious behavior helps us make healthy, informed decisions about what we eat. But when our stomachs begin to growl, too often they drown out any good advice coming from our brains. Unfortunately, the shortsighted decisions we make with our stomachs are having an increasingly negative effect on our health. Research into overeating and obesity has accelerated in recent years, and with good reason: excess weight is the most important risk factor for cardiovascular disease and diabetes. According to a study by researchers at the Centers for Disease Control and Prevention and the National Cancer Institute, obesity was associated with about 112,000 deaths in 2000 in the U.S. In addition, a 2002 study in the journal Health Affairs estimated annual medical spending on overweight and obese patients to be as much as 92.6 billionor 9.1 percent of the countrys health expenditures. Physicians define obesity as having a body mass index, or BMI, higher than 30. Anyone with a BMI above 25 is overweight. (You can calculate your own BMI at www.nhlbisupport.combmi) By these measures, about one third of American adults are overweight, and nearly another third are obese, according to the National Health and Nutrition Examination Survey, conducted between 2003 and 2004. topof page Stop Hormones In their quest for causes, scientists have long concentrated on metabolic hormones. In 1994 Jeffrey M. Friedman of the Rockefeller University discovered that adipose tissue, or fat, possesses a feedback mechanism by which it can block additional eating. Indeed, fat cells secrete a protein that passes through the blood to the hypothalamus in the brain, where it suppresses feelings of hunger. Friedman dubbed the substance leptin, from the Greek leptos, meaning thin. When researchers genetically engineered mice in which leptin could not function, the animals rapidly became obese. The results led some to speculate that obesity might stem from little more than a faulty feedback mechanismand not human behavior. On closer examination, however, this interpretation turned out to be too onesided. Leptin, we now know, also plays an important role in addictive behavior. Heroin addicted lab animals suffer even more during withdrawal if they are kept hungry. Perhaps this satiety hormone suppresses cravings not only for food but for certain drugs as well.