Dr.BariatricHTX said:

The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either.

Same experience, arrived at from the opposite direction. I had assumed I was the exception until I read this.

quinn_sf said:

The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the…

Correct, and worth adding that it is reversible. Nothing being described here is a one-way door, which changes how cautious it is reasonable to be.

quinn_sf said:

The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the…

That reframing is the part I needed. Sending this to two other people who asked me the same thing last week.

Adding the clinical framing, because it changes how the question reads. Worth answering the question that was asked rather than the one behind it. The narrow version usually has an answer; the broad version usually does not, and answering the broad one is how a thread stops being useful.

Moderator note: the sourcing question belongs in the vendor section and has been split out. No action needed from anybody.