It's not like they are healthy enough to breed or carry a baby.  Likewise someone 40 lbs overweight won't be able to be there for a wife and child if something serious happens to them. Sure, raw muscle is part of being able to look after one's family. But in the modern world the far more common threats are things like cancer. Things that take as much endurance as muscle to help with. It's not just being able to lift them. But to also deal with continual lack of sleep, ability to sprint to take care of things, etc.  I absolutely agree with the comment about fat women. But fat men let down their families in a very similar way.