If you gained extra weight you should know that your metabolism is not the same one that kept you lean before. You should understand that your new metabolism utilizes your current life style to store excess fat, and you need to modify your life style to prevent it from doing that, and to do that you should understand your metabolism and your food.
Swallowing diet pills or starving your body to slow down your metabolism and lose weight, is not the solution to your overweight problem, since they work temporarily, do harm to your body, and may be far from the right basics of weight loss.