Yes I was always very slim and fit in the 1950-1960 era.. I was born in 1942,so war years, and food rationing, but good cheap type meals,made by my grandmother,who lived with us, My own late Mum, wasn't a very good cook, but she did have to go out and do war work though.
I was married in 1967,aged 25,and was only 7st, which,was not then considered anorexic or anything, , All my girlfriends were slim also,
Not many people had a car, I used to cycle to work for many years,There were no junk food cafes around then, We just had a few fish and chip shops in our small town,usually having fish and chips on a Friday night, I used to like walking a lot, especially as my soon to be husband was a big outdoor type.
My personal fitness and keeping slim,was due to doing serious ballroom dancing for about five years.
And most kids growing up in the oldie days, were always playing outside (safely then ) so lots of skinny types around being always active.
You tend to get told off as an oldie,when you say the good old days, but good and bad it was, but I think its a case of knowing, that you should realise what food is best for you,and don't succumb to junkie stuff at all. and move around a lot, even with a stupid phone in tow ha ha.