Food Addiction Likened to Dependency on Hard Drugs

(March 29) -- High-fat, high-calorie foods pack the same addictive punch as hard drugs, according to new research on rats that could help explain compulsive eating, and therefore some cases of obesity, in humans.

Investigators at the Scripps Research Institute in Florida, whose study is published in this week's Nature Neuroscience, doled out different diets to three groups of rats. Over 40 days, all three were fed healthy, regular meals. For one group, that was it. But a second group was fed high-fat, high-calorie foods for an hour a day, and a third was offered unlimited access to junk-food treats.

The rats were fed everyday indulgences from the grocery store, including bacon, cakes and chips.

Before long, rats in the third group were not only obese but were noshing exclusively, and constantly, on the unhealthy fare. And although they'd been trained to expect a shock when exposed to a flash of light, the treat-loving rats didn't flinch at the stimulus -- they were too fixated on food.

When the research team performed brain scans on the rats, they concluded that the third group exhibited cerebral responses similar to those seen in drug addicts. The rats had fewer dopamine receptors, which indicate less capacity to experience pleasure. This brain change is a common characteristic among drug addicts.

Addiction overloads the brain's "pleasure centers," leading to increased tolerance for one's stimulus of choice, whether it's a drug or food. Enjoyable feelings require more and more input, leading to compulsive consumption.

"People know intuitively that there's more to [overeating] than just willpower," lead researcher Paul Kenny told CNN. "There's a system in the brain that's been turned on or over-activated, and that's driving [overeating] at some subconscious level."

Knowing how foods can affect the brain might help researchers reduce overeating in humans. In 2005, researchers led by Nora Volkow, current director of the National Institute on Drug Abuse, concluded that morbidly obese patients suffered from dysfunctional dopamine systems similar to those of drug addicts.

At the time, researchers were quick to point out that brain chemistry can be blamed only in rare instances. Lifestyle habits, dining choices, genetics, activity levels, mental health and hormones can all play a role in how much we eat, what we eat and how it affects our weight.

And that's why experts are hesitant to apply rat findings to humans: The mechanisms that affect our consumption are significantly more complex. But, notes Kenny, effective treatments for drug addictions might be worthwhile tools for dealing with the problem of compulsive eating.

"If we could develop therapeutics for drug addiction, those same drugs may be good for obesity as well," he said.