Is this really true about chocolate? I'm not convinced.
The amount of caffeine in chocolate is very small, really only traces. I checked the USDA nutrient laboratory, and according to them, an ounce of baking chocolate contains only 4mg of caffeine. This is tiny; my research on the caffeine content of tea and coffee says that a typical cup of tea is somewhere between 15 and 75mg, and coffee is from 85-135mg in a typical 8oz cup.
If the culprit is sugar, then blame sugar, not chocolate. Many chocolates are only very slightly sweet. For example, most 70% dark chocolate (which is one of the best things when you have a chocolate craving!) has very little sugar in the amount of it that you would normally eat.