Is drinking coffee bad on a diet?

Not coffee itself. Caffeine actually has been in the news quite a bit as of late because of some benefitial health benefits such as reducing diabetes, liver cancer, and parkinson's disease etc...It also has high antioxidant content and thus may have other health benefits. Unfiltered coffe may raise cholesterol a bit, but not filtered one. It is the condiments we add to coffee that have negative effects. Good luck.