The only time I'm ever represented in womens' magazines is as a "before" picture.
So I stopped reading them.
At the end of every clickbait article are ads "lose belly fat by eating this one weird food", "doctors hate her", and "new skinny pill that works too well".
Tabloids are constantly screaming "Celebrity beach bods! You won't believe who has let themselves go!" and "new diet gets you bikini ready in 6 weeks!".
In the snack section of any store, I see Weight Watchers, Skinny Cow, fat-free this and that.
Every stoplight has a billboard advertising a local liposuction clinic, with before and after pics.
Every restaurant commercial on tv shows men, women, children, black, white, Asian, young, old... but never fat people. "When you're here, you're family. And everyone in our family is thin." No fast food ad features fat people. They would never want you to associate their food with getting/ being fat. If you believed their commercials, you'd think only thin people go to McDonald's.
Only thin people buy and drive cars, trucks, and motorcycles.
Only thin people book vacations and cruises.
So I turned my tv off.
The message is literally everywhere I look, from my morning cereal box, to weight loss clinic ads on the front of the phone book, to the radio ads offering free "get ready for summer!" trial gym memberships, to songs about "dimes, tens, hotties". Everywhere I look, every store I enter, every doctors office, every errand I run has some message that being fat is ugly, horrible, the worst you can be.
A thin woman recently complained that her sister-in-law tells her to "eat a cheeseburger", so that means thin women get picked on, too!
Two people, same age, education, and experience interview for a job, one is thin, the other is fat. The thin person gets hired, every time- unless there is something seriously wrong with them. When asked, hiring managers answer that fat people seem lazy, out of control, disorganized, and unable to control their bodies, so it's a safer bet to go with the thinner applicant.
I once entered a clothing store that was popular with teens, to buy someone a gift card. I browsed a couple racks on my way to the register. The exceptionally thin sales girl approached me not to ask if I was finding everything ok, but to tell me, "I'm sorry, we don't carry extended sizes at this time." I replied that it was ok, I was shopping for someone else. She said, "You might have better luck at Dress Barn. Some of their stuff is really cute!"
Dress Barn. Yes, maybe I should get out of your hip skinny store before anyone sees me, and go buy my clothes from a store that is named for the farm structure that houses cows, horses, and other large animals.
My guess is you probably said something about a cupcake you were about to eat going straight to your size 6 thighs. You were probably wearing short shorts, maybe a halter top, because you are within the magic size range that society "allows" to wear those type of cute clothes. (Society only allows us to wear capris, flowing blouses with lots of smocking, large floral prints, embroidery, and color-blocking, lest we find our well-meaning friends and family have signed us up for a What Not To Wear intervention.)
And that's why your SIL told you to eat a cheeseburger.
Unless you are in it, you really don't see it.