To bra or not to bra? It's an age-old question. For years doctors assumed that bras helped keep our breasts perky, but then a French study argued they actually make the ligaments under our boobs weaker, which in turn makes them saggy. This hilarious video from Stuff Mom Never Told You explains that neither theory is correct. 

Genetic traits like skin elasticity, tissue density, and breast size are the real culprits for breast ptosis (a.k.a. boob sagging). Even if you're one of the lucky ones, gravity will get to all of us eventually. And factors like pregnancy, obesity, and smoking can affect your sag no matter what genes your momma gave you. 

READ THIS NEXT: This Video Explains Everything You've Ever Wondered About Boobs

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