What is carbon-friendly?

Can this result be true?  The guy claims that food production and refrigeration is so energy-expensive that it is more carbon-friendly to drive your car than to walk.  Walking requires that you eat more to make up the lost energy, as you can lose only so much weight (what’s the relevant margin here?  Ten feet of walking?  A lifetime of walking?).

It is also claimed that: "Paper bags cause more global warming than plastic."  Here is the book, I’ve ordered it and will report in due time.  In the meantime, here is Ezra’s coverage.

From Chicagoboyz, here is a good post on whether tangerines from a distance can be more carbon-friendly than local fruit.  Here is an earlier MR post on the same.