Caffiene Vs. Calories [Infographic]
 

but it is the sugar in these drinks that give the calorie not the caffeine
diet coke has no calories
furthermore caffeine is a fat burner, in fact, all the drugs you see on TV that tell you eat this and lose weight, is nothing more then concentrated caffeine

if caffeine was as effective as the TV commercials want us to believe then I should have been as thin as a needle right now