I'm one of the "will not give it up" people.
I have cut back significantly and limit myself to one can a day (part of my afternoon pick-me-up). I haven't noticed that it's made any huge difference one way or the other. I will say that I notice when I drink more diet soda, I drink less water ... and when I drink less water I feel sluggish and ... well, icky.
If I don't drink enough water I get headachy and bloated and my skin starts to feel dry. It could be partially psychological .. but I do think it's partially physiological as well. My body is used to being well-hydrated and subbing soda for water just doesn't cut it for me anymore.
YMMV and all that.
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