
Let me try to put things in perspective...

You are what you eat...


Food availability during war time...

Lifestyle...
The other huge factor was how people actually lived and what they did. Kids were more active and took gym classes and home ec in the 1940s and 1950s, where they learned how to prepare healthy food. Now all those classes are getting cut and eliminated from school curriculums which leads to kids being bigger.
On top of that adults are getting less and less sleep because of stress and outside factors, so their metabolism is goofed up, that can be a factor in weight gain.
There wasn't TV like there is now. People lead sedentary lives sitting in front of TVs, computer screens, and playing video games. That wasn't even thought of back then!

