I'd postulate that it isn't poor little old innocent by-stander sugar, but instead it's evil twin that big corporations have been using as a cheaper substitute---that industrial waste, high fructose corn syrup.
It can convert into fat very easily, whereas real sugar, while it can, won't usually. You won't get fat from pure sugar--but oh yes, that industrial waste is right at the front of that parade.
Get that high fructose corn syrup crap out of your diet, not sugar.