Wendy Foulds Mathes, PhD, is trying to teach rats to binge on Double Stuf Oreo cookies. You might think overstuffing yourself with yummy cookies would come naturally to a rodent, but it doesn't.
In fact, Foulds Mathes, a research assistant professor of psychiatry at the University of North Carolina School of Medicine, in Chapel Hill, and her colleagues are working hard to create behavior in rats that comes all too easily to some humans: binge eating. They control when the rats are given cookies, and then look for changes in the brain that might indicate that foods high in fat and sugar affect the brains' reward systems in a similar way to drugs or alcohol.
It's a serious question. People with bulimia or the condition known as binge eating disorder have an overwhelming, uncontrollable urge to binge on food in a way that seems similar to people with an addiction, experts say. In addition, they often struggle to change their behaviorwhich can cause potentially life-threatening health problems such as diabetes, hypertension, and heart arrhythmias.
"Many people have noticed that when people with eating disordersbulimia in generaltalk about the foods they binge on, it can sound a lot like how people with substance abuse problems talk about abusing drugs," says B. Timothy Walsh, MD, an eating-disorder researcher and professor of psychiatry at Columbia University Medical Center, in New York City.
The behaviors often go hand in hand, in fact. The American Psychological Association estimates that about 5 million Americans suffer from a diagnosable eating disorder. And according to a 2007 analysis of government data, roughly one-third and one-quarter of people with bulimia and binge-eating disorder, respectively, will also have an alcohol or drug problem at some point in their lives.
"It's not uncommon to have both problems," says Richard J. Frances, MD, a clinical professor of psychiatry at the New York University Langone Medical Center, in New York City, who works with people with both types of disorders. "The way people have trouble stopping, and the addictive aspect of both kinds of disordersand the compulsivityare similarities."
Foulds Mathes's research in rats is paying off. She and her colleagues have seen some brain changes, such as the release of neurotransmitters, in rats that binge on high-fat sugary treats that they suspect are similar to those in rats dependent on drugs or alcohol.
But you can only learn so much about binge eating from rodents, who aren't susceptible to peer pressure or other psychological and cultural factors thought to play a role in eating disorders in humans. "You can't ask a rat how it's feeling," Foulds Mathes says.
That's where the human studies come in handy. Researchers have found that, similar to what happens in rodents, chemicals such as dopamine are released in specific areas of the brain involved in reward processing when you eat something you find enjoyable.
And other studies have found high-calorie foods such as chocolate milkshakes activate "pleasure center" regions of the brain. But not everyone who encounters a chocolate milkshake feels compelled to consume 20 of them.
What triggers this compulsive behavior? Dr. Walsh and his team of researchers at the New York State Psychiatric Institute of Columbia University Medical Center have been studying patients with eating disorders, such as bulimia, for about 30 years. Their research suggests these reward pathways may be under-stimulated. In other words, people who start binging may begin a process that makes it harder for them to get the same reward from food, so they keep eating.
Allegra Broft, MD, a member of Dr. Walsh's team, used a type of brain scan known as positron emission tomography (PET), and found decreased levels of dopamine receptors in the brains of people with eating disorders. These were similar to the decreased levels seen in people with drug addictions, Dr. Broft says, but on a smaller scale.
Dr. Walsh says that this smaller magnitude is probably due to how the reward pathway is activated. Drugs such as cocaine, crack, and heroin "pack a whomp," he says. "That's why they're abusedthey're very potent drugs. So they will have a bigger effect on changes in brain chemistry in reward areas than natural rewards like tasty food." In addition to dopamine, other neurotransmitters such as serotonin are likely to be involved in eating disorders, Dr. Walsh says.
The future of eating-disorder treatment?
The addiction analogy isn't perfect. The brain mechanisms associated with eating disorders and addiction don't exactly overlap, and a binge eater or bulimic can't quit food cold turkey the way an alcoholic or a drug addict can sober up. Still, greater understanding about the brain networks that underlie both addiction and eating disorders could have important implications for treatment.
Experts tend to avoid the term "addiction" when talking about eating disorders because treatment approaches for the two conditions are so different, Dr. Walsh says. Although addicts try never to use or consume drugs or alcohol again, people with bulimia must learn how to have a more normal relationship with food, and to eat for nutrition.
"You can get over bulimia and live comfortably with foods you used to have problems with," Dr. Walsh says. Both cognitive behavioral therapy and antidepressants like Prozac (fluoxetine) can help people with bulimia, although antidepressants are not very useful for drug problems such as cocaine abuse, he adds.
Dr. Broft and Dr. Walsh hope their research ultimately finds more powerful cures for eating disorders, and perhaps one day prevents them. Not all people with eating disorders respond to treatment, and some respond only partly.
"I think it's very important to continue to pursue the neurobiology of addictions to substances and the neurobiology of eating disorders, and really try to understand how the neurobiological systems are affected," Dr. Walsh says. "What's similar and what's differentthat's the key. It would be very helpful in understanding and treatment if we understood those in more detail."