Austrian Society on Eating Disorders (OEGES)
Thanks to Andreas Karawautz for letting me know about the new Austrian Society on Eating Disorders (ASED or OEGES in German). Apparently, it is the only German speaking research society on eating disorders. The site also contains information in English, which is useful for English-speaking professionals looking for treatment resources.
I've also added these details to my post on National and International Eating Disorders Organisations for Professionals.