Get Active, less Carbon!
Venture Capitalist Joi Ito has a great post about his Vegan Diet, his swimming regimen, and he talks about the energy he gets from being active. He makes an interesting note that mass transit over cabs has contributed to his sense of well being. His scaling back of animal protein (i.e. meat) has also contributed to his generally good spirits. Meat is a huge carbon contributor through deforestation (note I'm not a vegetarian, but I try to have a few meat free days a week. Going Carbon Free is hard, but we call all shoot for less carbon)
I've had the belief that automobiles more than diet has contributed to our obesity crisis, but that was just based on my personal obeservations living in Taiwan where my diet became "worse" but I still lost weight.