Sugar is said to be as addictive as heroin, and probably it affects the same receptors in our brain. For sure, it increases blood sugar, and then insulin (our fat-storing hormone) is produced to regulate the blood sugar. Often, this causes a blood sugar drop that is lower than it should be, and then our body signals us to eat more sugar; so the whole sugar-thing can become a vicious cycle.
I try to stay away from sugar (and any other addictive foods); but that does not mean that I am 100% good on this. Sometimes, there is just that perfect piece of apple pie, and it is calling my name..... you know how that goes. But, for the most part, I stay away from sweet foods, and only use sweeteners like Splenda occasionally.