I know this is kind of an old thread, but I have always wondered the same thing. I quit drinking all carbonated beverages years ago because a diet doctor told me to. I drank nothing but tea, coffee and water for well over a year and it didn't seem to make any difference at all for me. I enjoy carbonation so eventually I went back to it. I have been dieting off and on since mid 2011 and I have diet pop every single day. I've lost 100 pounds so far, so I guess I can say it doesn't seem to hinder my weight loss. Although I have never tried cutting it out since I've been dieting to see if I would lose any faster without it. It's nice to know that others have reached their goals while drinking it daily. I quit smoking years ago and don't plan on going back to it, but I feel better since I stopped. When I quit drinking carbonated beverages I never noticed a difference in how I felt, so I guess that's why I don't see a reason to quit again since I really do enjoy it. I know the chemicals aren't good for me, but there are lots of natural foods that have poisons in them (don't ever eat apple or cherry seeds). I think it's all in the quantity and I drink more water than I do anything else. Some days I only have one can of pop, but other days I might have 3 or 4, just depends on what's going on.
I was on the Atkins diet from July 2011 to October 2012 and I lost 73 pounds. October 15, 2012 started WW's and got down to 255. Gained 25 pounds through the holidays, but got back on track June 2013. Got off track through the holidays again and gained back 10+ pounds
I will continue my journey to the end, no matter how long that takes.