This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.
Post #60 is right about the mechanism and I think understates the practical bit.
The most useful reply I ever got about Seven-day rolling was a request to state my units. It sounds like pedantry and it has saved me twice.
Coming back to post #58, because the follow-up matters more than the original answer.
Counterpoint on Seven-day rolling, offered without confidence: the same observation is consistent with a much duller explanation, and nobody has ruled the dull one out.
A seven-day rolling mean of daily readings has a much smaller standard error and makes most apparent plateaus and sudden drops disappear.
Checked the Seven-day rolling claim against the primary source this morning. It survives, with a narrower scope than the version quoted here. Posting the narrower scope.
I read post #63 twice before replying, because I had assumed the opposite.
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.
That is the shape of it. The detail is where I would expect to be corrected.
Longitudinal report with the method stated: same scale, same time of day, same conditions. A scale is a tool; use the same one each time. Consistency matters more than accuracy at capturing absolute weight.
Adding it in case it saves somebody the afternoon it cost me.
My position on Seven-day rolling is current rather than settled. I have revised it once already and I expect to again, so treat it accordingly.
Everything in post #69 holds. The case it does not cover is the one I have.
Two things can be true about Seven-day rolling at once: the mechanism is plausible and the evidence for the size of the effect is thin. Most of the argument here is people defending the first against attacks on the second.
Narrowing post #69, because the general version has more than one answer.
Maintenance series are the ones this subcategory needs most and receives least. The interesting questions all change once loss stops.
State the method before the numbers. Same scale, same time of day, same conditions — without that a series is a collection of readings rather than a measurement.
That is all the detail I have. Someone else will have more.
Practical note on Seven-day rolling: write down what you expect before you look. The number of times I have found what I went looking for is higher than chance would allow.
Post #74 answers the question as asked. The question underneath it is different.
I disagree with the framing of Seven-day rolling above, and I think it is a substantive disagreement rather than a terminological one. Setting out why, so it can be checked.
The reasoning depends on an assumption that is doing a lot of work and is never stated. If the assumption holds, the conclusion follows. I do not think it holds generally.
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.
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.
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.
The question underneath Seven-day rolling is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.
Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.
Post #80 and I disagree about the size of the effect, not about the direction.
I would keep Seven-day rolling and the decision it usually gets used for separate in this thread. They are related and they are not the same question, and merging them is why the last one went badly.
Small methodological point on Seven-day rolling: repeating a measurement is cheap and resolves most of what is being argued about here at no cost to anyone.
Understood, and I withdraw the assumption I opened with.
Post #84 put the caveat in the right place and I want to underline it.
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.
Seven-day rolling sits at the boundary between what this community can usefully discuss and what it cannot, and I think it falls on the discussable side, narrowly.
Post #86 is the version of this I will quote in future. One addition.
If a pattern survives a rolling-mean treatment it is worth explaining. Most do not, and that is the useful finding.
The literature is thinner on this than the confidence in the thread implies.
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