When I was a kid (the '80s and early '90s), we didn't know shit. Life was a frustrating/comforting maze of not knowing anything about anything and not having access to any information.
It's not that PMS doesn't exist — it's just that we tend to dismissively blame everything on PMS, as though women don't have any actual reasons to be sad or angry or bitter or resentful.
Even if I did eat a bucket of pancake-flavored ice cream for breakfast, burrito ice cream for lunch, and salisbury steak ice cream for dinner (OMPH GROMPH GROMPH), I still shouldn't have to justify my existence to the world.
If this middle-schooler is feeling pressure and shame on a national scale and wanting to lose weight because the Nike Corporation put his fat body on display to sell shoes, then that's creepy and depressing.