I never said they live at 3% body fat, I said they are known to get down to around that level. :good BUT! It is possible to maintain such body fat percentages... Michael Johnson, an olympic runner, had been noted for maintaining a body fat % below 3.
Re-read the first line of my previous post. Don't believe what you read, apparently Bruce Lee had 1% body fat. Impossible.
mhm... Well, then. The Prodogy, same advice stands! Just remember to never neglect your body of nutrients.
Bone weight as well. Something else interesting that does not come into consideration a lot of the times is bone weight. Some people have lighter bones, some people have heavier bones.