One thing to note is that chocolate does contain some amount of caffeine, or caffeine-like substance called theobromine. This is generally much less stimulating than the same amount of coffee, especially if you eat raw cacao (raw chocolate), but some people might not react well to it. Therefore, if you don't usually eat chocolate or drink coffee, it might be good to eat small amounts of chocolate at first to see if you feel well with it.
Still, for many, chocolate is an effective way to get a lot of the minerals that people are really "trying" to get through typical food. When you are low in minerals, over-eating is likely to be more prominent. Chocolate is one of the highest sources of some of the minerals that people are often lacking, such as magnesium and chromium, which makes it an incredible choice for weight-loss.