As for caffeine intake, I take plenty. Not from coffee, but from Coca-Cola. I'm almost ashamed to say it, but I'm addicted to it. It's of the "Zero" variety, so there are no calories, but there is caffeine (and other chemicals). I think I may have become immune to it by now, I don't sense any caffeine effect by drinking or not drinking coffee, as long as I take my daily fix of Coke.
There may be zero calories in Coke Zero but the artificial sweeteners in diet/zero drinks are more difficult for our body to process. It's advisable to take carbonated drinks as little as possible.