My guess is overtime, foods are now packed with sodium, sugar, and fats to make it more delicious — ppl love instant gratification 😋, why cook when you can buy a whole tub of mac n cheese for $5 🫠🥲.
My other guess…people were dying earlier back then due to poorer technology in health. Couldn’t survive long enough to get to BMI of 30. 🤷🏻♀️