Nowadays too many desk jobs. And the other reason for obesity is Netflix. Lots of sitting going on in this country. I need to exercise more myself.
I think you are onto part of it. I wear the same size dress slacks and shirts I did in high school and I weigh about 20 pounds less at age 69 then at 18-19. I once was about 25 extra pounds and my BP went sky high. I feel miserable if my stomach is not flat.