Paleo, Zone, IIFYM (If It Fits Your Macros), Flexible Dieting, the Rennaisance Diet... spend even a little bit of time on the interweb and you're sure to be overwhelmed by the torrent of helpful, if completely contradictory information out there. Dan John and Josh Hillis have provided a template to clear away the clutter, and get to why so many approaches CAN work, where there might be short-comings, and easy ways to implement.
At the end of the day, we really only have a few main concerns for our young athletes: Are they getting enough quality nutrition? If so, are they getting too much? If so, what's the easiest, simplest way to help with that? After that, almost everything is detailed optimization. The low hanging fruit really are as simple as adequate nutrition and not overdoing it.
(Full disclosure: When I'm being good, I generally eat clean (ie, Paleo-esque, grain-free, prioritization on meat, veggies, some fruit, some nuts, no sugar (ie, the original CrossFit recommendation) and don't tend to worry *too* much about overall calories. Eating clean food is so satiating that it can actually be pretty difficult to over-eat. Especially if you're paying attention to the veggies... )
Food Author Sheri Castle shows off two Zone blocks of vegetable-based carbs.