If junk food was available back in the olden days how come obesity rates were low?

Kids actually went outside to play and got exercise, the restaurants weren't on every street corner and people actually cooked their meals and sat around the same table in the kitchen and not in the living room watching television. People took their lunches to school and to work and folks ate a half way healthy breakfast. in the morning. And most restaurants weren't open 24 hours a day 7 days a week. Ant there weren't very many all you can eat buffets either. Those are some of the reasons.