Crystal Light, diet soft drinks... I know these are 0 carbs on the label but I've also heard that the additives can stall ketosis. If that's the case are there any other diet products I should be weary of?
Also I'm not sure what the carb threshold is on no carb days, how many carbs can you have while safely staying in ketosis?

By the way the aerobics are killing me while eating no carbs. but the fact that I'm 40 pounds overweight probably isn't helping.

Atkins is kind of screwed up. He sort of knows what he is talking about, yet he doesnt. I believe he says caffeine will pretent you from getting into ketosis. This isn't true. I've been taking a thermogenic fat burner and drinking diet soda and have been getting into ketosis just fine. I also know many other people who do as well.

I've heard anything below 80-100g carbs is almost technically ketosis. Although, with that high of an intake, you will most likely not show traces of ketones in your urine. To be safe, it's probably best to keep the carbs at or below 30. Induction is supposed to be carbs at 20g, but I don't buy that and I keep my carbs at 10 or below.

With regard to your excersize situation, ofcourse, it is MUCH harder without carbs. I believe it's because fat doesn't metabolize as quickly as carbs do..