Black coffee, nothing. But drinking too much coffee is very harmful to the stomach. Losing weight is not worth the loss. If you hurt yourself by losing weight, you can't make it up. Usually the diet is light, with less oil and less salt. Drink plenty of water, and occasionally drink oolong tea and green tea (not tea drinks, but brewed tea without calories). The oil content of coffee is actually very high. It is definitely not as good as drinking water.