We usually think of food and drugs as distinct categories. But they have a lot of similarities: They're both substances you put in your body, and many people find it hard not to go overboard -remember when "Bet you can't eat just one" was the slogan for Lays potato chips? There's been plenty of research into why this is, but a new study has found one more reason behind these parallels. It turns out that junk food can hit your system with the speed and intensity of a controlled substance.

- Pizza vs. Cucumber

In this study, researchers from the University of Michigan psychology department and the New York Obesity Research Center had participants look at a series of side-by-side photos of food - for instance, pizza alongside a cucumber - and identify which of the two foods shown they were more likely to experience "problems" with. Problems included struggling to cut down on consumption of the food, or losing control and eating too much of it. They were, in other words, signs of addiction. By the end of the study, they had compared every food on a list of 35 foods. The researchers had specifically chosen foods that fell into one of four categories: high in fat and refined sugar or carbohydrates, like chocolate or french fries; high in fat but not refined carbs, like cheese or bacon; high in refined carbs but not fat, like pretzels or soda; or low in fat and refined carbs, like broccoli or chicken.

Overall, the foods that the participants found most addictive were all highly processed - that is, altered to increase the level of fat and refined carbohydrates - with a high glycemic load. That's a measure of how much a food will raise your blood glucose levels after you eat it; a high glycemic load typically signifies low-quality carbohydrates. This held true for an initial population of 120 University of Michigan students, and for a more diverse group of 398 online participants found via Amazon's Mechanical Turk. Though the exact rankings of the addictive foods were slightly different for each population, everyone struggled with the same core snacks: chocolate, pizza, ice cream, cookies, cheeseburgers, and fries.

- The Science Behind Addictive Snacks

It makes sense that these foods would be more addictive than, say, grilled chicken, researchers argue. They have some key things in common with addictive drugs. They're consumed in high doses and absorbed rapidly, triggering sudden blood sugar spikes. Like drugs, they've also been processed - modified with extra fat and/or refined carbohydrates and stripped of fiber, protein, and water to better suit our cravings. Just as coca leaves aren't as addictive as their processed counterpart, cocaine, grilled chicken isn't as addictive as its fattier, carbier counterpart, fried chicken.

It's not just humans who find processed foods addictive, either. Rats can get addicted to them, too. They show signs of addiction when they're snacking on Double Stuf Oreos, for instance, but not when they're eating normal rat food. They'll also seek out highly processed snacks even if it means suffering some kind of punishment, like an electric shock. In other words, these foods have a power that transcends species.

This makes pretty intuitive sense. We all know that we're unlikely to binge on cucumber slices and more likely to binge on candy. However, this is the first scientific study to support the idea that processed foods are more addictive than naturally occurring ones - a result that's both obvious and important. It could be one of the many keys to controlling the obesity epidemic, slated to affect 85 percent of U.S. adults by 2030.

It could also, potentially, lead to changes in the law. "If properties of some foods are associated with addictive eating for some people, this may impact nutrition guidelines, as well as public policy initiatives such as marketing these foods to children," the lead author and University of Michigan psychology professor Erica Schulte said in a statement. If junk food really does hit the body like a drug, should we treat it like one?