"We have all these delicious foods out there, and we also have all these diets telling us to stop eating them and how to get control over our intake," said Dr. Nicole Avena, a Princeton University trained neuroscientist and psychologist, who has written more than 60 journal articles about diet, nutrition and overeating. Yet, she said, many people struggle to lose weight and eat well.

She visited Tucson to promote her new book, "Why Diets Fail."

"Diets fail," Avena explained, "because when you think about going on a diet, the idea is that eventually you are going to go off of a diet. And we know that's not how it works." Individuals have to change how they think about and act around food in order to make real changes, she added.

However, many people find it difficult to stick to a new way of eating. That may be because some foods are actually addictive, she said. Like addictive drugs, these foods can cause changes in one's brain and in one's behavior. A major culprit? Sugar.

"There's actually 56 different types of sugar," Avena said."There's lots of different names for things that are actually sugars that we don't always recognize them as such." As a consequence, it can be very difficult to avoid sugar.

New research on laboratory rats and humans shows that the excess consumption of sugar can activate or over-stimulate neurochemicals in the brain. The same thing happens when someone takes, what Avena called, drugs of abuse.

Just like with alcohol or cigarettes, not everyone is susceptible to sugar addiction. However, like with cigarettes, alcohol and other substances, people may experience cravings, withdrawal, difficulty cutting back and changes in tolerance to sugar.

"What the research is suggesting, is that the over-consumption of sugars in particular seems to activate these reward systems in the brain," Avena said. "And what happens is, this somewhat vicious cycle can emerge that is associated with a slew of changes in behavior."

Such behaviors include consuming more sugars and experiencing withdrawals when one tries to eliminate them from one's diet.