Were we fitter before the invention of Fitness?

I understand the theory that we're all getting fatter but I've rarely seen it demonstrated quite as clearly as it was last night on the Yesterday channel. The documentary was actually about the Great Train Robbery so it used lots of archive clips of police inspecting the crime scene, railwaymen loading trains and women and children gathering outside court buildings as the accused were smuggled in under blankets.

It's 1963. Everybody's thin. Everybody. It's startling how thin they are. Even the senior police officers may incline towards burliness but they're never what you'd call paunchy. The small boys and girls mugging for the cameras are Lowry figures. The overalls are hanging off the fingerprint experts sweeping Leatherslade Farm. Only the odd member of the gang is built as if he's a stranger to physical exertion.

I suppose none of this is surprising in the light of something else I learned yesterday. In the fifties the average housewife walked eight and a half miles a day. That's presumably made up of housework, taking the kids back and forth to school and shopping without a car. Eight and a half miles a day. Nowadays we'd call it a regime. None of those people in 1963 would have given any thought to their fitness. Most of the adults would have smoked. Their diet wouldn't have been the best. But in terms of body mass they must have been fitter in the days before the discovery of fitness.