well it depends on the product you're using. for me, when im on the diet i take diet pills and it really stops my food craving.
check the site on my source it really helps.
By surpressing your appetite - basically they are the same as speed. They work while you take them but as soon as you stop the weight goes back on and more. Use a sensible diet rather than pills. If you do go ahead with the pills - watch out for the mood swings.
Most just have a ton of caffeine to give you energy so you'll want to work out and stuff. Usually they're just water pills with caffeine that make you pee out a lot of water but you'll just replinish it eventually
its better to just eat healthy. cut out Salt and sugar !