[gambi]

He probably told you to cut it out becuase of the artificial sweetner aspartame, if you googel aspartame you'll see why he's trying to steer you away from it. They have found the diet drinks made with artificial sweetners make you hungrier. And who knows what other problems they cause.

I myself have tried to cut back, but it's hard. I have switched to only drinking diet sodas with splenda and limiting them to only a few times a week.

Oh I've also heard that caffeine can raise blood sugar.

Pretty much everything some way or another is going to end up bad for you, it stinks.