When Did Fat Start?

For some reason I started looking through my dad's high school yearbook last night. (Dad graduated from Mission High School in San Francisco, California, in 1941.) I don't think they called it a yearbook back then, but I can't recall what they called it, and it doesn't say in the book. Anyway, I couldn't help but notice how slim everyone was. That got me thinking about our obesity epidemic here in the USA. So then I got out my senior yearbook. (I graduated in 1970.) Again, everyone was slim. I looked at pictures of the "fat" people in my class. They weren't fat. They sure seemed fat at the time. Now I'm beginning to wonder when teens began to get fat. I'm thinking about looking at some yearbooks from 1970 until now to see when people started looking obese. If I ever get around to it, I'll write about it here.