A consensus-based decision making process on fasting terminology will be conducted using the Delphi technique. To this aim, experts around the world are invited.

The consensus-based decision making process on fasting terminology will include a maximum of five rounds of questionnaires that experts are invited to complete online using a pseudonym. Prof. Dr. med. Michalsen's department has prepared rough definitions of key terms for the questionnaire to be evaluated by the experts. These terms should serve as a starting point for the discussion. After each questionnaire round the experts' comments are reviewed by the project team and a new questionnaire with the suggested modifications from the previous round will be sent to the experts.

If consensus can't be reached by round three, a live-online-discussion will be held to facilitate the further proceedings.

The results are to be published in a peer-reviewed journal; individual statements will not be shared in the publication.

Inclusion Criteria:

• clinicians or scientists with at least 5 peer-reviewed publications on fasting or
• at least one peer-reviewed publication and 5 years of clinical experience with fasting

Exclusion Criteria:

- not more than 2 experts from one institution are allowed to participate

clinicians or scientists