Well there shouldn't be persay.. but the Zoloft is a suppressant for the seritonin and other endorphines that slow the metobolism so it can be difficult to achieve weight loss on a quick fix diet plan.
Most weight loss aids, won't help you lose a lot of weight; or if they do, chances are that you will gain it all back again once you stop using the product.
You would be much better off to implement some small lifestyle changes, such as drinking water instead of soda, eliminate sugary foods, as well as those made from white flour; switch to whole grains, brown rice, low/no fat dairy or other small changes. They don't all have to be made at once.
Incorporating a moderate exercise program will also do wonders.