Do the shallow atheists on here really think that Jesus was being so narrow in His words?
No, by and large the atheists - shallow or otherwise - are skeptical as to whether Jesus existed at all, and generally couldn't give two hoots what he said if he did exist. What we're worried about, in the main, is what people who believe they know what Jesus said think and want so see happen.
As far as any eternal life goes, the physical needs of the body really make no difference. They sustain your mortal life, which is a microscopic fleck of time in a grand scheme of things. So He's saying that it would be stupid to trade eternity to sustain the body. You need both to be complete. You have to mind the physical body and the spirit. Man cannot live a full spiritual life if his perspective is based solely on the physical side of bread alone.
And all you need do to justify that is give some sort of meaningful explanation of what 'spiritual' is... Good luck.
O.