It would help in answering this to know:
Do you already have a job with youth athletics and want to increase your skills and knowledge base?
If not, what sort of job have you targeted, for which you would like to apply?
Working with athletes requires a high degree of knowledge, as their competitive edge is maintained through intense attention to both fitness and nutrition.
You may need to consider going back to school to get a nutrition degree, or you may be able to take a nutritional course, such as ACE offers (and if you just want a short course that will let you answer general questions, as an adjunct to already having a fitness degree or certification the ACE training is well regarded, though there are others) “. the scope of practice for these are quite different, so knowing exactly what you will be doing or wish to be doing will help you understand how much training you will need to do it.