Exercise was not necessary until the mid-20th century

Most people didn't see exercise as necessary until the mid-20th century. Food scarcity meant people didn't overeat, and it didn't make sense to try to burn off the calories.

However, industrialization changed the nature of work and food production. Fewer farmers were doing physical labour, and more people were doing office desk jobs. The growth of automobile culture, the suburban sprawl, and the popularity of television, all led to a more sedentary lifestyle.