Pop and soft drinks are the Canadian terms for what Americans call "soda". In Canada, a soda is a mix of carbonated drink over ice cream.

Citric acid is a major ingredient of many soft drinks including Crsytal Lite and other mixes and Dr. Atkins's books warn that it stalls some people.

With that, aspartame and the caffeine in some diet drinks, you'll just have to try and see. Maybe it's better to leave the caffeine withdrawal until after you are safely into LC eating. And maybe, if a person had cut out colas & coffee right away, they'd be 10 pounds lighter already. It comes down to what you can do and still stick with the LC.