I don't know if this helps but I am on day 4 of induction and lost 2 pounds already. I am using aspartame for a sweetner, until I can adjust to the suggested one.
There are studies I believe that show Aspartame can slow weight loss...You can read more at the AtkinsCenter online.
I have friends who used the Atkins plan, used aspartame and lost all of their weight.
Maybe if you just use less or drink less soft drinks and see how your body responds.....
I hope that helps somewhat
Nan