after humans go into space and live in low/zero gravity situations the physical penalties for obesity are reduced and the fatties are able to grow to enormous sizes without being crushed to death under the weight of their own hideous mass. After a few generations the fatties have evolved bodies more in line with their excess nutritional intake and as everything else about them grows, so does their brains. The fattest of fatties grow super smart and super large and conquer humanity completely, possibly eating a lot of us in the process and eventually evolve to enormous space whales the size of planets and rule the universe.

Thats how it all plays out in the end. Fatties win bigtime.