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Junk food as addictive as drugs, says new neurological study

Posted Nov 24 2009 12:00am


Tis the season to eat pecan pies, Christmas cookies, cheese sticks, and other festive goodies. Right? Just for a month or so. Then we'll all go on diets!  Diet books' highest sales are right after the holidays. I've already gained a couple of pounds and it's not even Thanksgiving yet!  :o(

But after reading this study in Science News, which I'm about to describe, I'm going to take a little more care in tossing down the sweet and high-fat treats this season. Read what happened to these rats!  Sure they're rats, but they're mammals just like we are, and their brain physiology is far more similar to ours than it is different.  Listen up to what these scientists Paul Kenny and Paul Johnson found out about the addictive nature of junk food.

Neuroscientists Paul Kenny and Paul Johnson from Scripps Research Institute reported last month that rats fed a steady diet of high-fat junk food develop addictive behavior similar to heroin addiction!

The rats in the study were divided into two groups. One group was fed a healthy diet of high-nutrient, low-calorie chow. The other group was given unlimited amounts of junk food, which included Ho Hos (packaged cakes), bacon, cheesecake, pound cake and sausage.

The two researchers found that, for the junk-food rats, the pleasure centers in the brain became less responsive to the tasty high-fat food, requiring more and more food to stimulate the brain's pleasure centers. Consequently, the rats began to eat compulsively, taking in twice as many calories as the other group, and soon became obese.

Habituation to the high-fat diet was surprisingly fast. After only five days on the junk-food diet, the rats showed  "profound reductions" in the responsiveness of their brains' pleasure centers.  At this point, the rats "lose control" of their eating, said researcher Paul Kenny of Scripps. "This is the hallmark of addiction."

As another way to assess the impact of  junk-food on the rats' brains, the scientists used electrodes to stimulate the pleasure centers in the brains of both groups of rats.  The rats could control the amount of pleasurable stimulation by running on a wheel. The more they ran, the more pleasurable stimulation they felt. During this part of the experiment, the rats that were addicted to junk food ran more than the healthy-diet rats, suggesting that they  needed more stimulation of the pleasure center to feel good.

So what happened when the junk-food addicts were forced to go cold turkey and give up the cakes and bacon?  The addictive changes in the brain persisted for weeks, even after the rats' weights returned to normal.  In presenting their data at the Society for Neuroscience Annual Meeting in October of 2009, scientists Paul Kenny and Paul Johnson speculated that the addicted rats' response to food may be changed permanently.

Ack! Well then, maybe it's a good thing that my co-worker snatched up the last piece of pecan pie at work today.  There was nothing left but apple pie, and that was too wholesome for the mood I was in. I wanted something wickedly sweet.

But for real, I plan to keep in mind the five days to food addiction reported by these guys at Scripps, and exercise some control this season. Before it's too late!

Sources:  
Laura Sanders.  "Junk food turns rats into addicts. Bacon, cheesecake, Ho Hos alter brain's pleasures centers." Science News.  November 21, 2009.

Paul Johnson and Paul Kenny. "Society of Neuroscience Program."  'Neuroscience 2009' Conference. October 17-21, 2009.  Chicago.

Key words:: junk food, addiction, holiday food, high-fat foods, diet, nutrition
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