Strict rules about nutrition for young athletes are a big mistake, in my experience.
They put the child athlete in a serious conflict: the coach’s rules vs peer pressure / temptation.
All the best coaches I know now talk to kids about making “good choices”. Education will work, long term, for those kids who are serious about their sport.
The real problem are the parents of athletes. Far fewer than half where I live provide reasonably healthy food for their children. (I don’t blame them. They have plenty of challenges of their own.)
The best parent education I’ve ever seen are grocery store tours like the ones organized by Gymnastics British Colombia:
Registered Dietician, Christina Baxter, will take you on a tour of a typical grocery store and give you practical and useful information …
Even better is when the child comes along on the tour with Mom or Dad.
The Dieticians of Canada offer The Virtual Grocery Store, an on-line interactive game. (It’s not all that fun. The real store tour is better.)
To be honest, good nutrition is not one of the most important variables of training. I’ve known a few very successful athletes who can eat anything with no effect on performance.
UPDATE: Dana Brass noted that her club Marian Gymnastics in Canada organized grocery store tours in the 1990s. We copied that idea at Taiso Gymnastics, I recall.
UPDATE: Check Anna’s comment below too. She feels kids today are “over-fed, … bombarded with food choices”. Too trure
Gymnastics Coaching.com 