BMI in the protocol [Regulatives / Guidelines]
and I wish to point out the similarity to e.g. lab reports. When something is out of whack like SGOT a few points above the normal upper limit, the PI can always clear the subject for participation anyway, often with a relatively innocent "NCS" (or "CNS" or "OK" or "Fine" or "No problemo" etc) on source to indicate that although this is a little outside the planned range the subject is fit for trial. Same principle with the BMI and other inclusion criteria.
The decision is the investigator's.
You can be healthy without being normal, so to say.
Pass or fail!