Great question. I don't need a study to tell me that I'm an addict. When I crave something, it's hardly ever meat or broccoli. I usually crave foods that are very high in glycemic index and the more of those that I consume, the more I want them and I don't think I"ll ever be able to quit. I've included some interesting links.
I think it's complicated. Sugar is also how we were rewarded as children (for some people). You got a boo-boo? Here's some ice-cream. For other people there's an insulin response that happens so when they consume sugar, they get that energy burst and then the slump which makes them crave more sugar. Also, I believe that we have yeast colonies in our bodies and they feed on sugar. When we stop, they die off and that makes us feel sick so then we want more sugar.
Some people can have a little sugar and eat it in moderation. If you can do that, then it's ok to have that Snickers bar once in a while but for others (like me), having that bar will trigger me to binge and that is always followed by depression and physical illness. You have to do what's right for you.
To get more info on sugar, you might want to check Robert Lustig's videos on youtube. They have some really great info.
http://ajcn.nutrition.org/content/ea...64113.abstract
http://www.forbes.com/sites/alicegwa...to-your-brain/