I was having a giggle on a "fat person hate" thread on //fit/ today, and a few thoughts clicked.
I was told here once that the reasons gorillas can maintain their muscle mass on a leaf diet is due to their gut biome which assists in synthesizing proteins from leaves and grass. Fatties often complain that calories in/calories out doesn't work for them. Could it be that fat people just have a tremendously efficient gut biome that synthesizes proteins better than most humans?