Originally Posted by pvaudio
That last bit is a body image issue, but that has absolutely no relation to the majority of teenagers who lift weights simply to become better athletes.
That is my whole point. The OP was asking about a six pack - which is CLEARLY all about image.
Don't get me wrong, I fully endorse a healthy fit lifestyle and I truly believe that as a teenager you MUST be physically active. But pursuing fitness, health and strength is different than "sculpting" individual big muscles.
Where it becomes worrying and detrimental to development (and creating issues later in life) is when kids start to obsess over a body image put forth by guys like "the situation".
This obsession can push them to eat an unbalanced diet, spend a fortune on crappy powders and damage joints by lifting too hard, too early on.