The long and short of the matter:

1) Caffiene causes dehydration. The diet you are on currently is already highly diuretic. So the need for replacement fluids increases.

2) Artificial sweeteners have been known to trigger insulin release in some people causing a stalling effect on weight loss.

3) Aspartame is a pretty scarey toxic sweetener, causing headaches and other ailments.

4) Dr Atkin's limits our artificial sweeteners to 3 a day. Including cans of pop.

Aren't you glad you asked?