Ultrasound and skinfolds: operator dependence in practice posts 61–77

Post #59 and I disagree about the size of the effect, not about the direction.

The most useful protocol is the one you will actually repeat identically. An imperfect measurement repeated consistently beats a better one repeated carelessly.

Fine by me. I had wanted a stronger conclusion and there is not one available.

Source for the ultrasound and skinfolds figure, since it was asked for. It is in the discussion rather than the abstract, which is why the version circulating is stronger than the paper is.

Reading the surrounding paragraph is worth the two minutes. The authors are more careful than their summarisers.

Narrowing post #63, because the general version has more than one answer.

Speaking only to ultrasound and skinfolds as I have actually seen it, rather than as it is usually described: the effect is real, it is smaller than the thread suggests, and the variance between people is larger than the effect.

Worth separating two things that post #63 runs together.

Ultrasound: thickness of subcutaneous fat at specific sites. Less standardised than DXA and operator-dependent. Useful as a supplementary measure but not as a primary method.

Happy to expand any of that if it is the useful part.

This follows post #63 rather than contradicting it.

The useful distinction on ultrasound and skinfolds is between what was measured and what was inferred from it. Both end up in the same sentence and only one of them has error bars.

Neither method is capable of detecting the month-to-month changes that people report detecting month to month.

Two claims get bundled together under ultrasound and skinfolds and they need separating. The descriptive one — this is what was observed — is usually well supported. The causal one — this is why — usually is not.

Almost every disagreement in threads like this one dissolves once you say which of the two you are making.

Same experience here, different supplier, so it is at least not unique to one of them.

Post #67 is the version of this I will quote in future. One addition.

Adding the boring version of ultrasound and skinfolds, because the interesting version keeps getting posted and the boring one is usually right.

Check the ordinary explanations, in order, and stop when one of them accounts for what you are seeing. Most of the time the second one does.

Percentage body fat is a ratio, so it changes when either component changes. A rising percentage during weight loss is arithmetic before it is physiology.

On post #68 — agreed on the reasoning, with one qualification.

Summarising the ultrasound and skinfolds thread so far, since it is long and the answer is buried: the first reply has the method, the fourth has the correction to it, and the rest is people agreeing at length.

What I can speak to on ultrasound and skinfolds is narrow, so I will keep it narrow rather than generalising from it. Beyond that boundary I do not know.

The most useful protocol is the one you will actually repeat identically. An imperfect measurement repeated consistently beats a better one repeated carelessly.