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Is a micronutrient panel worth drawing after six months of low intake?

Asked 2 May 2024Modified 23 months agoViewed 24k times
6

I have three DEXA scans on the same scanner at twelve-week intervals, fasted, same time of day.

This is a planning question. I know what my options are; I do not know how to weigh them.

What I want is the minimum viable version, which I suspect is smaller than what I would design.

What is the minimum version of this that is still defensible?

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EM
askedeoin_mcgarry16k182 May 2024
5The arithmetic checks out. I ran the same numbers and got the same result. – rune_thoresen 27 days ago
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5 Answers

Accepted answer first, then by votes
109

Accepted answer

Concretely, what the data supports is narrower than what gets recommended, so it is worth separating the two.

Protein target, worked: at 88 kg, a target of 1.6 g/kg is 88 × 1.6 = 141 g per day. Spread across three eating occasions that is roughly 47 g each, and the leucine threshold for a maximal muscle protein synthetic response is met at around 2.5 to 3 g of leucine, which corresponds to roughly 30 to 40 g of a high-quality protein. So three meals at 40 g plus one 25 g snack gets you to 145 g and clears the per-meal threshold each time. On 900 kcal that leaves about 340 kcal for everything else, which is the actual constraint.

The regain trajectory after stopping is roughly a mirror of the loss trajectory, and it is not primarily a willpower phenomenon. Appetite signalling returns, energy expenditure remains suppressed relative to the original mass, and the two combine. That is an argument for a maintenance plan existing before the stop, rather than an argument against stopping.

SURMOUNT-4 provides the cleanest maintenance-versus-withdrawal contrast available in the class, and it is the reference for any claim about what happens after stopping[1].

Train, eat the protein, measure something functional, and give the trend three months before you interpret it.

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answered · acceptedgrainne_ahearn13k1618 Aug 2024
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95

On the detail: start with the arithmetic, because the answer to the practical question is usually a number and the number is usually achievable.

Hydration state moves a DEXA lean-mass figure directly, because the algorithm assigns water to the lean compartment. Scanning fasted, at the same time of day, before training and without a recent high-carbohydrate day is the difference between a comparable sequence and a noisy one. Bioelectrical impedance is far more sensitive to hydration again, which is why its trend is unusable at this timescale.

DEXA precision is better than people assume for fat mass and worse than people assume for lean mass in a single scan — the least significant change for regional lean mass on a well-maintained scanner is on the order of a few per cent. That means two scans three months apart can differ without anything having happened, and it means a scan sequence needs to be at least three points before a trend is interpretable.

Two resistance sessions a week and a protein target you actually hit will do more than any refinement beyond them.

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DV
answeredDr_Ilse_Vandenberg78k24829 Aug 2024
49

Concretely, a plateau at four to six months is the expected shape of the curve, not a failure of it. Energy expenditure falls with mass, and the deficit closes itself unless intake falls further.

The minimum effective resistance-training dose in a deficit is lower than most programmes assume. Two sessions a week covering the major movement patterns, with loads taken close to failure, is sufficient to retain most of what would otherwise be lost. Volume beyond that adds recovery cost that a large energy deficit is poorly placed to pay.

The first four weeks of loss is substantially fluid and glycogen. Each gram of stored glycogen carries roughly three grams of water, and total glycogen is on the order of 400 to 500 g, so the obligatory water shift alone accounts for a couple of kilograms. This is why the first month looks dramatic and the second looks like a plateau when in fact the fat-loss rate has not changed.

The evidence for a higher protein intake preserving lean mass during an energy deficit is reasonably strong in resistance-trained populations and weaker in sedentary ones, with the meta-analytic estimates supporting intakes in the region of 1.6 g/kg over lower intakes when training is present[1].

A maintenance plan written before you need it is worth more than a better loss plan.

edited 20 Jun 2024 by coldpack_88 — reworded for clarity after a comment

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answeredcoldpack_8837k3823 May 2024
4Useful. I have added the accept threshold suggestion to my own notes. – Dr_Bram_Verhoeven 3 months ago
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41

On the detail: the mechanism is worth having straight, because it predicts which interventions can work and which cannot.

Food noise returning is not obviously tolerance. Receptor desensitisation is one hypothesis; a second is that the initial effect was partly novelty and partly the steep early deficit, and a third is that intake has drifted upward and the signal is being outcompeted rather than weakened. The three make different predictions about what a dose increase would do.

The body-composition substudies in the major programmes consistently report that the proportion of weight lost as fat mass is approximately three quarters or better, with the lean-mass fraction falling within the range seen in dietary weight loss of comparable magnitude[1].

The caveat is that population averages tell you about populations. Your own trajectory is a sample of one and should be read as a trend, not as a deviation from a published mean.

Measure strength as well as mass. It is cheaper, it is less noisy, and it is closer to what you actually care about.

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MF
answeredmeniscus_film34k3812 May 2024
7Have you seen anything published on this, or is it inference from the mechanism? – dermot_kiely 3 months ago
6Useful. I have added the accept threshold suggestion to my own notes. – Dr_Priya_Raghunathan 2 months ago
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35

Mechanically, the commonly quoted figures for lean-mass loss are mostly measurement artefacts, and the artefact is well understood: fat-free mass as measured includes water and glycogen, both of which fall early and neither of which is contractile tissue.

Fibre at very low total intake is a trap. Soluble fibre needs water and motility to work; insoluble fibre adds bulk to a slow transit. At 900 kcal a day with delayed gastric emptying, an osmotic agent is more predictable than a bulking one, and adequate fluid is doing more work than either.

Worth stating that a DEXA sequence is only as good as its protocol consistency, and most people’s sequences are not consistent enough to support the conclusions drawn from them.

The plateau is arithmetic. Treat it as arithmetic and the response follows.

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RC
answeredRP_C1885k15816 Jul 2024
5Is there a reason to prefer the second method over the first, other than cost? – bac_or_bust 6 days ago
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