Hahah you guys are just so far off base it's not even funny. I have zero idea where you are getting your information, but there aren't that many guys out there maintaining under 10% body fat. **** body builders that are peaking for a competition hit 5%, and they can't even maintain that for more than a day or two. Call me crazy, but you thinking you got an accurate body fat % in high school is hilarious. Much more likely you stepped on a digital scale or something.
The guys walking around under 10% body fat you can see every single muscle in their stomach. Wawrinka you can only see a suggestion of abs, I doubt he's much under 15%. Don't get me wrong he's obviously super fit, but none of these guys outside maybe Monfils or Novak have exceptionally low body fat for an athlete.
You're right. 5% is extremely low. But 10% is not for an elite athlete. 15% is just your average office worker who eats right and exercises 3 times a week. Stan is closer to 10%