She was a size 16..? She didn't look that big when I saw her wax figure in Madame Tussauds ....
Sizing was complete different back then. According to her dressmaker, her measurements were:
Height: 5 feet, 5½ inches
Weight: 118-140 pounds
Bust: 35-37 inches
Waist: 22-23 inches
Hips: 35-36 inches
Bra size: 36D
At the time, that was around UK 16/US 12, although the size she wore fluctuated with her weight. At any rate, the fatties today who glorify her apparently have no concept of vanity sizing/size inflation, and I'm betting are far from a 22" waist.
http://jezebel.com/5299793/for-the-last-time-what-size-was-marilyn-monroe