He is less likely to be attacked at the beginning of the disaster. But what after a few days, or weeks? He's a little more lethargic than others due to lack of nutrition. Should you plan to survive for just a few days or for the "long haul"?

And of course, this ignores the use of guile and weapons, possible cooperation and communication of his enemies... these are the things that humans excel at.

Being strong has obvious advantages, but people don't always stop to think about the disadvantages. Everything is a trade off of one thing vs. another. 5% body fat sucks if you're in the Donner party starving, even if you can lift a truck over your head!