After the first couple of weeks of South Beach diet (which bans sugar and fruit in "phase 1"), I had a cheat day. I ate a couple of servings of cookies with refined sugar in them. Ooooh, they tasted good!
But... (there's always a "but") they sat in my stomach, made me feel nauseous, and then I had some issues in the bathroom. I have been staying on diet and away from refined sugar, ever since. I do well with small amounts of honey or agave nectar, though.
MG1: Get down to 170 by end of June | MG2: Reduce body fat % from 34 to 30 by July 20th