While it may be true that the American lifestyle is more sedentary, I don't think obesity can be entirely or even mostly explained by that. AFAIK diet generally affects weight more than exercise does; if your diet is energy-heavy, it's very difficult (without being an athlete) to exercise enough to consume as much as your energy surplus from the diet is.
I don't have any references or numbers to back that up, but that's what I've understood from what I've read in papers and heard from some people who apparently did the math.
With that said, physical activity has lots of benefits beyond just weight loss, and it would be worth it to make one's lifestyle non-sedentary in any case.
I don't have any references or numbers to back that up, but that's what I've understood from what I've read in papers and heard from some people who apparently did the math.
With that said, physical activity has lots of benefits beyond just weight loss, and it would be worth it to make one's lifestyle non-sedentary in any case.