Is fasting classified as a study procedure - therefore should a subject give consent before beginning a fast, for example for a screening blood test?

My understanding over the last few years has been that the requirement for no trial procedure to take place before consent extends to asking potential subjects to fast for screening blood tests. But I have just come across a REC approved protocol which appears to permit this.

I am wondering about the impact on insurance and indemnity, if a subject were to have e.g. a dizzy spell due to fasting. Also I am slightly concerned that patients are coming in fasted, and then have to sign a consent form before they have their bloods taken and before they can have something to eat, and therefore their opportunity to ask questions might be influenced by a wish not to prolong proceedings.