Shantii, I've done P90X for over 9 months and I'm quite aware about Carbs vs Protein vs Fat. Protein is the hardest of the three to be broken down so the more protein you take, the more calories your body burns because your body needs to work a lot.

White Rice and other carbs do provide instant energy , sorta similar to the energy provided by sugar but it isn't a sustained energy. Your blood sugar spikes up instantly and after a while, there's a steep decline and this does no good to your body. On the otherhand, complex carbs likes Wheat Bread ensures that the rise of blood sugar is gradual and the energy stays intact for longer time frame.

I'm not saying that you should completely ignore white stuff but while it brings you no good, its substitutes will help you tremendously. Bear in mind, this bahun bro is looking for ways to drop weight.