Dr. med. Katharina Fleig studied Human Medicine at the Hannover Medical School, the University of Tartu in Estonia, and the University Hospital St. Gallen, Switzerland (2017–2024). She was awarded a university scholarship from the Studienstiftung des deutschen Volkes (2020–2024), the Lower Saxony Scholarship (2020 and 2023), and the Lower Saxony Science Prize in the category ‘Students – Volunteering’ (2022). During her studies, she worked as a student research assistant at the Project "SICKO - Sicherheit in der Kinderonkologie" (Prof. Dr. Lorenz Grigull and Dr. Urs Mücke) at Hannover Medical School (2019–2023). She completed her medical doctoral thesis in the Department of Medical Sociology at Hannover Medical School (Prof. Dr. Siegfried Geyer) with 'magna cum laude' in 2024.

Since September 2024, she has been working as an assistant physician at the Department of Psychosomatic Medicine and Psychotherapy at Ulm University Hospital (Prof. Dr. Harald Gündel). At the Seminar for Psychotherapeutic training from the Department of Psychosomatic Medicine and Psychotherapy she is currently completing her psychotherapeutic training.

As a Clinician Scientist funded by the German Centre for Child and Adolescent Health, Dr. med. Katharina Fleig has joined the Department of Clinical and Biological Psychology (Prof. Dr. Iris-Tatjana Kolassa) in April 2025. Her research focuses on the role of nutrition in the pathophysiology and treatment of mental health disorders in children, adolescents and adults. She is currently coordinating a partial project of the study 'MitoSwitch ', investigating the relationship between nutrition and brain metabolism in mental and neurological disorders.