The Coffee Diet
The theory behind the coffee diet is that coffee contains caffeine and caffeine can increase your metabolic rate by up to 10%. Increasing your metabolic rate lets you eat more calories and stay the same weight, or if you eat fewer calories than your body needs then you will lose weight.
However, there is a catch. As soon as you start to add milk, creamer, sugar etc your coffee diet goes right out of the window as any calories you may burn as a result of the caffeine effect on your metabolism can easily be used up by the additions.