No one doing manual labor for 60+ hours a week is morbidly obese.

Rather significant leap to take given the average hours worked per week in the US are over 40 and the % of US adults classified as obese is something like 40% or more as well - lots of candidate individuals out there. You really going to claim it's impossible for someone to be doing manual labor 60+ hours a week to pay rent and also have weight problems? Exercise doesn't automatically make you lose weight, high calorie intake or metabolic issues etc could cancel it out no problem. If it was as simple as 'just exercise a lot' weight issues wouldn't be so widespread.

I don't know about morbidly but have definitely seen many manual laborers that would be considered obese.

If you want to be thin, spend >80% of your effort in the kitchen. If you want to be strong, join a gym.

And also did you have a working kitchen? Access to a decent grocery store? Were you free from constant stress about how you would pay rent?

People don’t have those things any more than they do now 50 years ago when people weighed less.

They also didn't have grocery stores full of elaborate corn subsidy byproducts.