Blacks are notoriously low in the Big Five trait known as conscientiousness. They will lack self-control involved in eating better, and the self-discipline to establish better eating habits.  It is also possible that blacks are genetically different in how over-consumption is dealt with. It seems like white people should be the ones that are prone to storing tons of fat with little effort. It is also possible that they are being affected differently by chemicals and even by high meat consumption. From what I've heard, they mostly ate plants in Africa with all kinds of fruit trees and edible plants and roots all over the place.