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."