Medically speaking, I can say that I have seen people of African descent who have the same skin disease he claimed to have (Vitiligo). And the affected areas of their body did very much look like the skin tone he had in his later years. My own feeling is that he had a disease and later ended up having to somehow arrive at one skin tone. So whatever that entailed, yes, I think he did alter his skin color, but not to become "white".
I believe Mr. Jackson probably suffered from body dysmorphic disorder, and his endless plastic surgeries are really a sad commentary that surgeons would work on someone who really does not need surgery. Such a shame, and a sad loss. I hope he is at peace wherever he is.