[OMFG!You'reActuallySmart!]

There would be an issue if your past condition negatively affected your performance as a dietician in some way. If you tell your future employer about your past condition, then it would raise many flags and there may be an evaluation (formal or informal) as to how you currently are. Alternatively, some employers may not feel comfortable because of the increased chances that you may become a liability from your past conditions re-emerging or not fully recovered. Either way, telling the employer about this will raise many flags and they may not be as in favour of hiring you.

As for becoming a registered dietician, I'm not sure it will affect you because as long as you can properly perform then there may be no issues with that. They likely would not prevent you just because you did suffer from an eating disorder as it matters how you currently are.