A research team from the University of Michigan and Columbia University's New York Obesity Research Center looked into common addictive foods. What they found can explain a lot of things: highly processed foods share the several traits with abusive drugs. Those pizza cravings at 3 a.m. can somehow make sense now.

The team analyzed 35 different foods that people just can't stop eating. They surveyed 120 undergraduates at the University of Michigan and around 400 adults. The team used the Yale Food Addiction Scale, developed by psychologist and lead author of the study Ashley Gearhardt, to assess food addiction risk.

Chocolate reigned supreme and topped the list. It was followed by crowd favorites such as ice cream, French fries, pizza and cookies. Crowd pleasers like cheese, bacon, pretzels, fried chicken, soda and cake also graduated in the top 20 list.

Processed foods have higher levels of glycemic load and fat compared to the non-processed ones. They also found that processed foods are closely associated with eating disorders or behaviors that mimic addiction.

"Processing appears to be an essential distinguishing factor for whether a food is associated with behavioral indicators of addictive-like eating. Highly processed foods are altered to be particularly rewarding through the addition of fats and/or refined carbohydrates (like white flour and sugar)," wrote the researchers who pointed out that addictive substances are seldom in their original form. For instance, poppy is not addictive until it is processed into a refined state (opium). Grapes, while delicious in its fresh state, is not as addictive until it becomes wine. As for cacao, we all know what happens when it becomes chocolate.

Symptoms of food addiction include loss of control when it comes to quantity intake, inability to stop or cut down intake despite the presence of strong desire and continued use regardless of existing negative effects. Food addiction has been connected to emotional reactivity and high impulsivity, both are similar effects of substance abuse conditions. Both substance-dependent patients and food addicts revealed a similar biological pattern of reward-inclined dysfunction as shown in neuroimaging analysis. Researchers found there is an increased activity in parts of the brain related to the reward system when given food cues. This increased activation in the same region is present in patients with substance-abuse illnesses.

The researchers published their findings in the U.S. National Library of Medicine.