Dr. A says that caffeine is a problem because it causes you to produce more insulin, which causes you to have the same problems that eating bad carbs does. You should limit yourself to 2 servings a day (be careful...a serving is 8 oz. of liquid...) if at all possible. Here's the quote from the book (pp. 56-57):
Coffee, of course, contains no sugar on it's own. Peaople have grown accustomed to hearing doctors advise against excesses, but I don't think they're all that bad in moderation. Some diets steer people twoard decaf for the simple reason that caffeine does stimulate the pancreas to produce insulin, which is the last thing an overweight person needs. Still, the effect isn't all that great, and if a cup or two of coffee a day makes you happy, I think you should feel free. Tea may actually play a role in the prevention of heart attack and prostate cancer.
Note that he says if you want to have a cup or two
of coffee...not a grande latte three times a day.
I find that when I drink a lot of diet soda, I notice an increased appetite for carbs and fruit, and less weight loss.
Later on in the book, there's a testimony from Katie A., who says:
I was also a tremendous caffeine drinker back then. I was drinking a six-pack of soda every day--Diet Coke, or Diet Pepsi, or Tab. But it definitely was not caffeine-free, and I learned later that the caffeine was an appetite stimulant for me.
One of the things I love about SBD is that it encourages us to find what works for our own bodies. Obviously, if you are not seeing side effects from caffeine and your doctor thinks it's okay for you to consume the amount that you do, go for it. But if you aren't sure what it will do to you or you've never tried drinking less to see if it helps, I'd try that too. Figure out what works for you.