Genius insight on butt selfies.

One fitness influencer wants you to know that social media is all about illusions—no ifs, ands, or butts.

Sia Cooper, who runs the popular Instagram account @diaryofafitmommyofficial, often shares side-by-side images of her body to denounce unrealistic beauty standards and point out how different angles can influence what a person looks like on camera.

Last week, she posted brilliant insight into butt selfies—showing her followers how pulling up your underwear a certain way can totally change the look of your booty.

“PSA: UNDERWEAR PLACEMENT MATTERS,” Cooper captioned a set of mirror selfies. “If you hike your undies up really high, it’ll give an illusion of a tinker waist and bigger bum. Just another popular trick amongst Instagram fitness models! So don’t be fooled.”

This side-by-side was not a suggestion that her followers lift their undies up next time they take a belfie. In an honest disclosure, she provided an all-too-relatable postscript: “Having a 24/7 wedgie is not fun under any circumstances.”

Commenters praised Cooper for her transparency and thanked her for a much-needed reminder about the almost too-perfect body parts you see on your feed. A couple of days later, she illustrated her point by posting a photo of her “real booty” and then her “IG booty” with repositioned underwear.

“It’s amazing what a little bending forward, hiking up your underwear, arching your back, and sticking your booty out can do,” she wrote. “A picture is just a split second. We all look different from different angles.”