The study, which is published in the journal Nature Neuroscience analyzed three groups of rats.

One group was given a balanced diet or standard chow, another was given standard chow and limited access to junk food and one group received standard chow and unlimited access to junk food.

The group that was allowed to devour all the donuts, chips and chocolate lost complete control over their eating and became obese.

Not only did these rats pack on the pounds, but they also started to show changes in their brain functioning that mimic that of a drug addict.

When researchers looked into the brains of these rats, they found a decreased level of dopamine D2 receptor, the chemical that stimulates feelings of reward in the brain.

As the rats continued to splurge on twinkies, the overstimulation of their reward pathways decreased D2 receptor levels, perpetuating their need to eat more and more junk food.

“The brain has been overstimulated by the junk food, as a result it responds by lowering the D2 levels in its brain to help normalize its response to this food,” Paul Kenny, the study’s senior author and associate professor at Scripps Research Institute in Florida, told TheDailyPlanet.com.

“But in doing so it predisposes the animal or the human to developing compulsive behaviour towards food, because that’s what the D2 does in the brain, it regulates habit formation and compulsion.”

You can also be born with a decreased level of D2 receptors, making you more at risk to developing addictions, Kenny said.

"If you’re born with lower D2, you’re perfectly normal, it just means you may have greater vulnerability towards developing compulsive-like behaviours towards drugs or palatable food,” said Kenny. “We think that’s why you’re predisposed [to gaining weight], you’re almost halfway down the path.”

Kenny also said the study’s results may be very important in today’s society.

Statistics Canada reports 51 per cent of Canadians aged 12 and older were obese or overweight in 2008. In Toronto alone, 41 per cent were obese or overweight.

This study can serve as a cautionary tale to individuals who struggle with food, Kenny said.

“Having considerably lower D2 may predispose you to developing substance abuse disorders or overeating. And it may take a long, long, long time before your brain can normalize after you’ve stopped consuming the food.”

But he added the study can also help people understand that willpower is not the only thing in play when trying to avoid that piece of cheesecake.

He said the road to better health can be difficult, but not impossible. When you overeat, it becomes habitual, he described. But it is possible to break this habit.

“There may be changes in brain chemistry but it doesn’t mean they’re irreversible, it just means you have to be aware of that and know that they need a lot of work. You have to control what you eat and be on top of it”

Compulsive behaviours can be directed towards something that’s unnatural, like drugs, or things that are natural, like food.

The same type of therapy used for alcoholics or drug addicts might also be affective for overeaters.

However, Kenny said research is being done on anti-addiction medication that could also help with overeating addictions.

“There is an underlying neurobiology for this process and it can be difficult to control it but just be aware, it is supposed to be difficult to control," said Kenny.

"The brain has been altered but it’s not impossible, you just have to be very motivated and try and be aware of what sets off your cravings, what makes you overeat, and try avoid those situations.”