Dr.NutriCornell said:

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

Adding the part of the answer the thread has not reached. It helps to say which part of this you are uncertain about. A precise question gets a precise answer; a general one gets everybody’s favourite anecdote.

One concrete data point for the thread. If you are comparing against somebody else’s result, check that you are comparing the same measurement taken the same way. Most of the apparent contradictions in these threads dissolve at that step.

One thing that is still open after Dr.NutriCornell’s answer:

How much of the SELECT benefit is plausibly independent of the weight loss, and whether that distinction changes anything practical?

dave_SLC said:

If you are comparing against somebody else’s result, check that you are comparing the same measurement taken the same way.

I read this differently from dave_SLC, on substance rather than tone. Filing an objection on the n=1 problem. Personal experience is genuine evidence about one person and very weak evidence about anybody else, and this thread keeps promoting the first into the second.

Reporting back.

Closing this out. What actually changed my mind was the point about waiting for a trend instead of reading a single measurement, which is embarrassing in hindsight and worth saying anyway.