Our ancestors did not often have an abundance of food or eat a lot every day. Most Romans only ate 1 meal a day, and our evolutionary ancestors regularly faced

Our ancestors did not often have an abundance of food or eat a lot every day. Most Romans only ate 1 meal a day, and our evolutionary ancestors regularly faced days without food. Fatness was historically a signal of wealth. It was even rare to find someone fat as recent as the 1800s as you noted (and the reason had less to do with exercise than caloric intake). Really, the abundance of food didn't start happening until recent times with modern preservation techniques, industrial farming, and food processing (which also allowed for more calorie packed foods). The tractor wasn't even widespread until the 1910s, when it took 1.5 hours for horses to plow an acre of farmland. Nowadays it takes 5 minutes.