Junk food is addictive: Study

Rats Became “Addicted” to Fatty Food

Fatty, high-calorie foods can be as addictive as heroine, and could cause compulsive eating disorder and obesity, according to a new study

Experimenting with rats, researchers found that overconsumption of high-calorie food triggers responses which are similar to brain reactions to addiction.

“Obesity may be a form of compulsive eating. Other treatments in development for other forms of compulsion, for example drug addiction, may be very useful for the treatment of obesity,” researcher Paul Kenny of The Scripps Research Institute in Florida said.

Fat Donald by DonMak. CC 3.0 License. Click image to enlarge.

The obese rats were found to have fewer receptors for dopamine, a brain chemical that causes euphoria and reward, as it does in  drug-addicted humans.

Kenny and colleagues went on a shopping spree at a local grocery store hunting for fatty food.

“We basically bought all of the stuff that people really like—Ding-Dongs, cheesecake, bacon, sausage, the stuff that you enjoy, but you really shouldn’t eat too often,” he said.

One of the three groups of rats used for the experiment were fed high-calorie food. The group soon developed a liking for the fatty food and continued to eat unabated, quickly becoming obese, Kenny said.

The rats in the experiment had also been trained to expect a minor shock when exposed to a light. But when the rats that had unlimited access to high-calorie food were shown the light, they did not respond to the potential danger, Kenny said. Instead, they continued to eat their snacks.

Addiction

Dopamine Pathways – Serotonin Pathways. Brain pathways affected by drugs of abuse. The dopamine and serotonin pathways are two brain systems affected by drugs of abuse. They are illustrated here.  By altering activity in these pathways, abused substances can influence their function. Dopamine neurons (shown in yellow) influence pleasure, motivation, motor function and saliency of stimuli or events. Serotonin (shown in red) plays a role in learning, memory, sleep and mood. (source: USgov drug abuse site). Click image to enlarge.

“What we’re seeing in our animals is very similar to what you’d see in humans who overindulge,” he said. “It seemed that it was okay, from what we could tell, to enjoy snack foods, but if you repeatedly overindulge, that’s where the problem comes in.”

To see how far the rats were affected by [addicted to] their compulsive eating habit despite adverse consequences, they were trained that a painful electric shock would follow a flash of light.

The rats in the other two group, which had limited or no access to junk food, avoided the shock, whereas the “addicted” rats continued eating. “We see the same thing in animals with extended access to cocaine,” says Kenny.

The study of rats may not be directly related to causes of human obesity, however it could provide an understanding of how the brain mechanisms for food addiction work and help develop appropriate therapies, the researchers said.

“Once we start to consider obesity and pathological overeating as a psychiatric illness we’re going to move a lot closer towards understanding how to come up with therapies or treatments,” says Jon Davis, an addiction biologist at the University of Cincinnati in Ohio.

About 70 percent of adults and 35 percent of children in the US are obese or overweight and cost of treating obesity-related diseases could top $150 billion this year.

Related Links:

• Addiction Science: From Molecules to Managed Care

• People are fat ‘because they don’t enjoy eating’