The carbon emissions used to maintain me are approximately equal to (if not less than) the average North American who drives around everywhere. And because I stay (relatively) in shape, my body tends to use the calories more efficiently than someone who doesn't stay in shape. I am also less of a drain on the medical system.

I'm also curious about the "ridiculously less efficient" comment. Do you have any numbers? Compared to an average internal combustion engine car, driving in city traffic, with a single average driver (burning however many calories our bodies burn at "idle"), does a person on a bicycle burn more energy going the same distance? I find that very hard to believe...

Maybe a full busload of passengers would burn less per person, but the average North American commuter travels alone in their sedan.