There is much said about this, and it is a bit conflicting. First, understand that according to the USDA two cups of black coffee combine to provide just over one calorie. So, as a drink that’t not water, the calorie content is about as low as you can get. Granted, adding a truck load of milk and sugar changes that slightly if that’s what you do.
Beyond that, there are some studies that report that caffeine may slightly boost weight loss. This is achieved in two ways. Caffeine may serve to suppress your appetite a bit, which means that you should eat less. Second, it may slightly increase metabolism and heat in your body for burning fat. Neither of these claims has the weight of credible research behind it.
On the other hand, when people are in a bad mood, they tend to eat more. According to my wife and all my friends who drink coffee, this amazing elixir always improves their mood. So, even if it doesn’t make you lose weight, it’ll at least make you feel better, and with almost no calories, it can’t hurt.