There are a lot of Shakes out there that promise things, but I stick to the fundamentals. P90X, If I am correct, is a strength training, aerobic+anaerobic workout designed to fool the body out of the "Plateau" effect. condition the body to produce small amounts of fast-twitch muscle fibers in return a higher amount of slow-twitch fibers.
GNC %100 whey protein, contains 21 grams protein, less than 1 grams of milk sugars(fructose, sucrose, lactose, & galactose) around 100 calories per 21 grams of protein/serving. It's perfect for building lean muscles, but not any sugars for your body to run on, so it helps your body get used to using fat as an energy producer. A small amount of creatine is included, but not enough to be considered for loading.
I prefered NO2. Argenine Alpha Ketoglutarate. Really good and healthy vasodilator. Helps with blood flow, and also helps the body convert fat to energy by helping the body make more mitchondria in each cell. Mitochondria are the power houses of energy production in cells, so with more in each cell, more fat can be used as energy.
If you decide to get serious, there would be a lot more to know and a lot more research i woud recommend. I could help you if you need, hope some of this helps!