Namely, laziness. I agree with this article completely, even if it did come off track a bit defending the obese w/ all the links to studies.

Global warming is only very loosely related to our food consumption; as the author alluded to, SUV-drivers likely produce much more pollution.

In short: if you want to save your body, go on a diet; if you want to save the planet, put your car on a diet.

To conflate obesity with global warming is feel-goodism: I'm not a fat ass, so I'm not part of the larger problem. Or, I'm dieting! I drive to the gym in my Hummer!

It's lazy to connect these two very dissimilar phenomina; it's much easier to just take everything we feel bad about as a nation and mush it up into a giant ball of wish-fulfillment. But no ammount of worrying about your wastline will improve the air or your child's asthma, and trading in your SUV for a Prius is no substitute for diet and exercise.