Why did people back in the 70s and 80s looked so skinny?! 😳😳😳

I saw photo of my parents and they were SKINNY!!!! I mean even the women. That isn’t normal. Most women nowadays are thicker and fuller. I heard men that they don’t like skinny women. My dad was a skinny teenager and my mom was a skinny child/preteen.
How come people were skinnier back then? I envy them. Cher was SKINNY! Even my grandma was thin!