Fair point. I thought more on the lines of "we search people who want to fast. We will provide medical supervision and a controlled environment where you can do that, while we take notes. If you want to quit, you can at any time." (I assume with contract you mean something like "you have to fast for x days, if not you are in breach of contract" - is that correct?)

I just mean a contract agreeing to a study at all. "What gets measured gets done." Etc.

I am under the close supervision of my 30 old son and have been since he was 13. It's a completely different dynamic than reporting results to a doctor or lab for a study.