From a sociological perspective, here's what I have seen change in my 40years of living in the good ole USA that has lead us to where we are at:
1. Barbie Dolls used to be very popular. She had long blonde hair, skinny waist, long legs, nice big boobs, and pretty eyes. Everybody in America found Barbie attractive. At some point the "do-gooders" claimed that Barbie created BODY IMAGE issues for little girls. She was responsible for suicides, low self esteem, and eating disorders in young women. So the push for a more "realistic" FAT Barbie was started. Basically the bar that physical attractiveness was measured against was lowered to appease the whiners.
2. TV shows in the 80's and early 90's always had lots of hot girls in skimpy outfits. Charlies Angels, Dukes of Hazard, Fall Guy, 3's Company, Bay Watch, Etc. That helped create expectations of what a female should look like. We don't have anything close to this anymore.
3. Rock music and even country music video's on MTV, VH1, CMT, TNN all had tons of hot girls in their videos.
4. Super Models were a big deal in the late 80's early 90's. We had Cindy Crawford, Elle MacPherson, Carmen Electra, Kathy Ireland, Naomi Campbell, Tyra Banks.
5. You couldn't walk into an automotive shop without seeing a swimsuit calendar or topless calendar in some mechanic's tool box. Oil field workers, farmers, truck drivers always had a mini calendar stuck to the dash of their vehicle of these same girls. Mud Flap girl was seen every where and on the majority of over the road trucks.
6. Beauty pageants were popular. Miss America, Miss Universe, Miss Teen USA. We even had a beauty pageant for girls at the high school level back in the mid 80's.
Then the politically correct police came along, and took all of that away. They claimed it created unrealistic expectations for young women, it objectified women, and shamed men for liking that sort of stuff.
So these 6 things that helped drive "pop culture", which women strive to mimic, helped keep the fat epidemic in check. You don't see this type of influence these days.