The most important recent article on orthorexia is Thomas Dunn’s 2014 paper Microthinking about Micronutrients. Many others can be found on PubMed. Simply insert “orthorexia” into the search bar.
In addition, here are some links to full text articles:
Prevalence in Turkey
Donini Orthorexia Nervosa – Dimension of the phenomena
Donini Orthorexia Questionaire