You engage in physical activity when it is cool (first thing in the morning and last thing at night) and then dismiss heat as a factor?!?! Having lived in the

You engage in physical activity when it is cool (first thing in the morning and last thing at night) and then dismiss heat as a factor?!?! Having lived in the southern US (albeit Austin, which is not completely unbearable during summer days) I remember how strange the adjustment was when I first arrived. No one walks anywhere if they can help it: you leave your air-conditioned house in your air-conditioned car and drive to your air-conditioned office, at lunch you drive somewhere else and then at the end of the day you drive home. As you indirectly point out, physical activity requires setting aside specific times and is not something that you casually do over the course of the day. Poor and uneducated does not help, but there are a lot of poor and uneducated places in the US and around the world that do not have the same absurd levels of obesity. Air-conditioning and the lifestyle that developed around this invention are a major contributor to obesity levels in the south.