Years ago people were skinny. And it wasn’t just centuries ago. A few decades ago we were thinner.
A while back someone here on FR posted a link to youtube videos of a 1960’s program called Soul Train. See how thin people were back then. I was amazed.
https://www.youtube.com/watch?v=lODBVM802H8
That’s when soda bottles were small - 10 oz bottles- and cheeseburgers were half the size they are now.
I doubt you could find this many thin people all in one place now.
Of course the Soul Train crowd were professional dancers.
One trip to Wal Mart will confirm that maybe one person in ten is of a normal/skinny body conformation.
It turned about 1977. Dr. Jason Fung explains it all. He uses controlled studies from publications like JAMA and NEJM to illustrate his reasoning.