It turns out there is no problem with caffeine on a low carb program. In fact, it can be a big help. Well, caffeine turns you into a yellow toothed spaz. Being a spaz burns more calories than being a couch potato. While you're a spaz, you generally find better things to do than stuff your face with carbs.
Caffeine also has some appetite suppressing qualities.
I wouldn't toy with the recipe by getting more caffeine. At the very least, you should be taking a daily multi-vitamin. Not doing so can cause a variety of cravings or whack your metabolism. Maybe even lead to health probs. Once in a while I'll take some extra potassium or zinc.