For Cari Banks, one of the hardest things to say no to is food.
"I could eat half a pack of Oreos and milk and consider it nothing," she said. "I would eat it, pretty much without thinking."
But new research shows Banks' sweet tooth could actually be more like substance abuse.
Dr. Joe McClernon at Duke University studies the brains of people who are addicted to drugs, such as the nicotine in cigarettes. He says that for many obese people, junk food can trigger the same response in the brain.
"You can see activation when smokers are looking at pictures of people smoking, and the same thing when overweight individuals look at food cues," said McClernon, an associate professor in the Department of Psychiatry and Behavioral Sciences at Duke University Medical Center and director of the Health Behavior Neuroscience Research Program. "We see activation in areas involved in visual attention.
"We also see activation in both cases in a region called the striatum," McClernon added. "It's the part of your brain that tells you whether something is something you want to go after, or if it's something you want to avoid. But it's also the part of the brain that's involved in learning habits."
A new study by researchers at the Scripps Research Institute in Florida found similar results in rats. Pleasure centers in the brains of those fed high-fat, high-calorie food became less responsive over time -- a signal that the rats were becoming addicted. The rats started to eat more and more. They even went for the junk food when they had to endure an electric shock to get it.
"Your brain reacts almost identically to [that of] a cocaine addict looking at cocaine," said Dr. Louis J. Aronne, a clinical professor at Weill Cornell Medical School and former president of The Obesity Society. "And the interesting thing is that someone who is obese has even more similarity to the cocaine addict. ... In many ways, they can be addicted to junk food."