Junk food elicits addictive behavior in rats similar to that caused by heroin, a new study finds. Pleasure centers in the brains of rats addicted to high-fat, high-calorie diets become less responsive as bingeing wears on, making the rats consume more and more food, researchers reported October 20. The findings may help explain how changes in the brain could lead people to overeat. Click here to read the whole story.