Casein protein powders are more expensive than whey, but it can be stored longer in your body. They require more time to break down because it takes longer for the body to digest them. However, if you are serious about losing weight, you will want to ingest as much protein as you possibly can. It is impossible to stay skinny if you don't consume enough calories, so make sure you get plenty of greens, veggies, and fresh fruits to keep your metabolism up. You don't want your metabolism to slow down, because it will make it harder to lose weight.