We didn't need a scientific study to prove what most of us have known all along: Pizza is the most addictive food. Still, it doesn't hurt to have verified proof of this long-held suspicion.

According to a University of Michigan study published in the U.S. National Library of Medicine, pizza was named the top food to make people display addictive tendencies. In the study, pizza was ranked number one for the most "problematic" food item as "as indicated by addictive-like eating behaviors described in the YFAS (Yale Food Addiction Scale)."

Unsurprisingly, highly-processed foods and foods with added amounts of fat and/or refined carbohydrates had higher rates of addictive-like eating behaviors. "Nine out of the ten foods at the top of the list were highly processed and high in both fat and refined carbohydrates," wrote the study's authors. "Soda (not diet) was the exception, which is highly processed and high in refined carbohydrates, but not fat."

Other top ranked yet addictive-like foods in the study includes many people's favorites: chocolate, chips, cookies, ice cream and french fries. The least-addictive foods in the study were also not surprising: carrots, beans, apples and brown rice, with cucumbers ranked last.

But why is pizza so addictive? Most likely, it is a mix of contributing factors. Besides being a highly-processed food with refined carbohydrates, pizza is smothered in cheese. Cheese contains the casein protein which is found in all milk products. When digested, casein releases casomorphins which stimulate opioid receptors. Opioid receptors are part of the opioid system which controls pain, reward and addictive behaviors.

So does this mean you should stop eating pizza? Really, it's a personal decision. Most people wouldn't say they're addicted to pizza if they enjoy eating it. But like many (but not all) highly-processed foods, it should probably be eaten in moderation.