This is half the reason I avoid sugar. The other half is that it can trigger migraines for me. (I also avoid caffeine for the same reason.) I also don't eat much fruit for the same reasons. I seem to be OK with small amounts of blueberries and blackberries, but most of the sweeter fruits have too much sugar for me to handle.
I'm also allergic to wheat. Put those two things together, and most group food-sharing events are pretty much out for me. I recently started a new job, and on my first day the company hosted a "New Hire Bagel Breakfast" to provide a somewhat social time for me to meet people. It was an impressive spread of bagels, cream cheeses and various jams...and everyone seemed to like it a lot. I didn't have anything, which didn't bother me at all, but the HR person who coordinated it was bothered that everyone was eating but me.

