If you opt to participate, you must comply with the research agreements. Sometimes, for example, you are not allowed to eat, or you will have to take a medicinal product at a certain point in time.
It may be that there are certain things that you are not allowed to eat, or you will have to keep a diary. You must also cooperate with checks and examinations.
It is important that you comply with the agreements, otherwise the research will not go as planned and the outcomes will then no longer be reliable. If you do not comply with the agreements, the researcher may decide that you are no longer able to participate.