Age Limit

According to a site I saw, a contestant had to be 10-15 to compete on GUTS. However, on a site I saw while using Google a couple years ago, they had to be 11-14 to compete on Global GUTS. Is this because there weren't many 10 and 15 year olds who competed on GUTS? I only remember seeing 3 contestants who were 15; and they were all in the 1st season. I saw some who were 10; 1 was in the 2nd season and the rest in the 1st. Am I correct about this?