Seven-day rolling means and why weekly readings mislead — one year on

On the subject in the title: Seven-day rolling means and why weekly readings mislead — one year on Working notes rather than a conclusion.

Asking about Seven-day rolling directly, because I have read four threads on it and each answered a slightly different question.

The version I want answered is the narrow one: given the method stated below, is the result within what anyone else has seen? I am not asking what it means yet.

Method, numbers and the two assumptions I am aware of making are below. If the assumptions are wrong that is more useful to me than agreement.

Day-to-day body mass varies by more than a kilogram on hydration, glycogen and gut contents alone. A weekly reading is one noisy sample of that distribution.

If the premise is wrong, everything after it is decoration.

Right — I had this wrong and I am glad to have read it before it mattered.

An update on my earlier Seven-day rolling post: the pattern held for another six weeks and then stopped, which I did not predict and cannot explain.

Distinguishing three things in the Seven-day rolling discussion that keep getting used interchangeably: the observation, the proposed mechanism, and the recommendation that gets attached to both.

Post #6 answers the question as asked. The question underneath it is different.

Self-reported intake is optimistic in a consistent direction, and saying so in your own report is more credible than not.

I would not lead a decision with this, but I would not ignore it either.

Weighing daily and reporting weekly is a better protocol than weighing weekly, because it separates the measurement frequency from the reporting frequency.

A guess, clearly labelled as one.

The arithmetic in post #6 is right; the assumption feeding it is the part to check.

Seven-day rolling would be much easier to settle if anyone reported the denominator. Almost nobody reports the denominator.

Answering the question post #8 raises rather than the one it answers.

Seasonal patterns: some people report weight loss is slower in winter than summer. Body composition and activity changes might contribute. Noting the season is useful context.

That is the practical version. The rigorous version is longer and says the same thing.

That matches what I have seen, for whatever a single anecdote is worth.

Picking up post #10: that is the part I would want checked first.

Worth stating the null on Seven-day rolling before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one.

I had written a reply contradicting post #12 and deleted it. Here is what survived.

Menstrual cycle: for people who menstruate, weight can shift by several pounds across the cycle due to fluid retention and other factors. Noting cycle phase when weighing reduces apparent noise.

Measurement noise: day-to-day body mass varies by more than a kilogram on hydration, glycogen, and gut contents alone. A weekly reading is a single noisy sample of a distribution. A seven-day rolling mean of daily readings has much lower noise.