There is no magic using the EC stack, it will give you an energy boost and burn some extra calories in the day. Be careful doing cardio when using it, it makes my heart race like crazy.

The only weight you would gain back if you stop using it is water weight, due to the caffeine being a diuretic. This is assuming you still keep your calories in check and stay active. Obviously if you exercise less when you stop taking them, your calorie deficit may no longer be there making you gain fat.