the thing I find with coffee (I drink 3-4 cups a week, about every other day) is that if I have more than usual, the caffeine makes my appetite go away, and I'll go several hours without eating, but then when the caffeine wears off I am ravenous and feel like I could eat my shoe. The other thing to think about is what you are putting in - cream, sugar, syrups, etc can add calories, carbs, fat and sugar.
I've started having a cup of green tea every morning but in addition to my occasional coffee, not in place of it.