Collecting this in one place because it comes up every few weeks and the answer is always assembled from scratch. It is about fatigue, and it is deliberately narrow — everything I am not confident about is marked as such.
Mostly the deficit, and the useful part of that answer is that it is testable. Fatigue driven by a deficit tracks intake, improves within a day or two of eating properly, and worsens on the days you eat least. Fatigue that is flat regardless of intake, or that arrives on a fixed day after dosing, is behaving like a drug effect. Before assuming either, rule out the boring causes — iron, B12, thyroid, and sleep — because a fast deficit unmasks deficiencies that were previously subclinical.
The commonest reversible cause in practice is inadequate protein plus inadequate sodium, not iron. People restrict salt at the same time as calories without noticing.
Worth checking before concluding it is the drug: ferritin, B12, TSH, and total intake for three honest days. Two of those four explain most cases.
What I am after is whether the fatigue is a direct drug effect or simply the caloric deficit, because the answer changes what you do about it. Practical detail welcome, however dull — the duller the better.
Dr.NutriCornell said:Mostly the deficit, and the useful part of that answer is that it is testable.
That is right for the common case. Whether it is right for the case being asked about depends on a detail that has not been given.
Dr.NutriCornell said:Mostly the deficit, and the useful part of that answer is that it is testable.
This is where I part company with the consensus forming above. The counter-case has not been addressed. Somebody upthread described the situation that does not fit, and the thread moved on rather than engaging with it, which is the failure mode this board is supposed to avoid.
Certified reference materials, analytical reagents, and research-grade standards for peptide verification. Trusted by laboratories worldwide.
Shop Reference StandardsThis one has a reasonably settled answer, so here it is. There is a difference between no evidence and evidence of no effect, and this subject is one where the two get swapped freely in both directions.
TrialNerd_Beth said:Whether it is right for the case being asked about depends on a detail that has not been given.
Can confirm. Same sequence, different timescale. I had assumed I was the exception until I read this.