Obesity has long been blamed on weak willpower, overeating, genetics and lack of exercise. Now scientists increasingly are seeing signs that suggest there may be an additional contributor: food addiction.
Monday night and again today, dozens of the nation's leading researchers in obesity, nutrition and addiction planned to discuss whether food has addictive properties for some people. They're gathering in New Haven, Conn., at a meeting sponsored by Yale University's Rudd Center for Food Policy and Obesity.
"We believe that there is sufficient science to suggest there is something to this, so we are bringing the leading authorities together to decide whether food addiction is real and what the underlying psychology and biology might be," says Kelly Brownell, director of the Rudd Center.
"It's surprising that our field has overlooked this concept for so long," he says. "Society blames obesity only on the people who have it and has been close-minded to other explanations."
Support for the idea of food addiction comes from animal and human studies, including brain imaging research on humans, says Mark Gold, chief of addiction medicine at the McKnight Brain Institute at the University of Florida, who is a co-chair for the meeting.
In a medical setting, "we evaluated people who were too heavy to leave their reclining chairs and too big to walk out the doorway," he says. "They do not eat to survive. They love eating and spent the day planning their new takeout choices."
Psychiatrist Nora Volkow, director of the National Institute on Drug Abuse, a speaker at the meeting, says the research in this area is complicated, but most people's weight problems aren't caused by food addiction.
Some studies focus on dopamine, a neurotransmitter in the brain associated with pleasure and reward. "Impaired function of the brain dopamine system could make some people more vulnerable to compulsive eating, which could lead to morbid obesity," Volkow says. She did groundbreaking research in this area while at the U.S. Department of Energy's Brookhaven (N.Y.) National Laboratory.
For some compulsive eaters, the drive to eat is so intense that it overshadows the motivation to engage in other rewarding activities, and it becomes difficult to exercise self-control, she says. This is similar to the compulsion that an addict feels to take drugs, she says. "When this occurs, the compulsive eating behavior can interfere with their well-being and their health."
But there are many differences between addiction to drugs and the intense compulsion for food, she says. Food is necessary for survival, and eating is a complex behavior involving many different hormones and systems in the body, not just the pleasure/reward system, Volkow says. "There are multiple factors that determine how much people eat and what they eat."
She does not believe that most people are overweight because their brains' dopamine systems don't function properly. There are many causes of excess weight, including unhealthful eating habits, lack of exercise, genetic vulnerability and stress, she says.
Although there is no official definition of food addiction, Gold defines it in much the same way as other substance dependence: "Eating too much despite consequences, even dire consequences to health; being preoccupied with food, food preparation and meals; trying and failing to cut back on food intake; feeling guilty about eating and overeating."
He believes some foods are more addictive than others. "It may be that doughnuts with high fat and high sugar cause more brain reward than soup."
Others pooh-pooh the idea of food addiction. "This is a dumbing down of the term 'addiction,' " says Rick Berman, executive director of the Center for Consumer Freedom, a group financed by the restaurant and food industry. "The term is being overused. People are not holding up convenience stores to get their hands on Twinkies.
"Lots of people love cheesecake and would eat it whenever it's offered, but I wouldn't call that an addiction," he says. "The issue here is the intensity of people's cravings, and those are going to differ."