People with a low starting BMI: where the evidence stops

Posting this under the heading it deserves: People with a low starting BMI: where the evidence stops Everything below is what sits behind that.

Asking about a population rather than about a person.

The published trials in this class mostly enrolled a fairly specific group, and the questions here frequently come from people well outside it. I would like to understand what the honest position is when someone falls outside the studied population: not "it is fine" and not "there is no data", but what the reasoning actually looks like.

The opening post describes the usual case. This is about the unusual one.

Body weight at the extremes of the studied range affects exposure and the trials rarely reported enough to say by how much.

I would want the raw data before agreeing with my own summary of it.

The opening post is the version of this I will quote in future. One addition.

Almost every population discussed here was excluded from the pivotal trials, which means the evidence base is observational at best and absent at worst.

Someone should write this up properly, and it should probably not be me.

Post-surgical populations, particularly after procedures affecting the gastrointestinal tract, interact with a delayed-emptying mechanism in ways that need specialist input.

Take it as a starting point and not as a specification.

The arithmetic in post #4 is right; the assumption feeding it is the part to check.

Extrapolating a point estimate to somebody well outside the enrolled range should be described as an extrapolation every time it is done.

One case, stated as one case.

Answering the question post #2 raises rather than the one it answers.

Dedicated trials in under-studied populations are the only real remedy and several are ongoing, which is worth saying rather than speculating.

Stating my assumptions rather than smuggling them in.

Being outside the studied population does not mean a treatment is unsafe. It means the usual evidence is not available and the reasoning has to be explicit.

Where a population is under-studied, registry data accumulates first and is confounded by indication in ways that are hard to correct.

Adding a note of thanks rather than an opinion. I did not know most of that.

The absence of a reported signal in a population that was barely enrolled is not evidence about that population.

Pregnancy and breastfeeding are the clearest cases where the answer is that the trials excluded them and the labelling reflects that exclusion.

It is the sort of thing that seems obvious in retrospect and was not at the time.

Post #10 answers the question as asked. The question underneath it is different.

Adolescent evidence exists for some compounds in this class and is a separate approval decision with its own trials rather than an extension of the adult data.

The evidence for this is thinner than the way I have phrased it suggests.

Athletes and people in substantial training loads are effectively unstudied, and the questions asked here about performance have no trial evidence behind them at all.