How much protein in grams do I need at 74 kg on 1,400 kcal a day?

Question

Setup, so nobody has to ask: 74 kg · 1,400 kcal. I have worked this out and I would like someone to find the error, because I suspect there is one. My working so far, for the record, is below, and I am fairly sure the error is in the unit conversion rather than the algebra. How many significant figures are actually justified here?

bea_castellanos · Accepted Answer

The relevant detail is that start with the arithmetic, because the answer to the practical question is usually a number and the number is usually achievable. 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. Protein target arithmetic Body mass 1.2 g/kg 1.6 g/kg 2.0 g/kg Per meal at 1.6 (÷3) 62 kg 74 g 99 g 124 g 33 g 74 kg 89 g 118 g 148 g 39 g 88 kg 106 g 141 g 176 g 47 g 103 kg 124 g 165 g 206 g 55 g 124 kg 149 g 198 g 248 g 66 g At roughly 4 kcal per gram, 141 g of protein is about 564 kcal — a substantial fraction of a 900 kcal budget, which is the real constraint. Mechanically, absolute strength holds up better than scale weight during a deficit for a straightforward reason: strength is substantially neural and skill-based, and the contractile tissue you retain is being trained harder relative to its size. Grip strength and repetition maxima are therefore lagging indicators of muscle loss rather than leading ones, which is an argument for measuring both. Adaptive thermogenesis — a fall in energy expenditure beyond that predicted by the change in body composition — is documented across weight-loss interventions and is the mechanistic basis for the plateau being expected rather than anomalous. I would be careful with the supplement literature here; effect sizes are small, the studies are mostly in trained young men, and generalisation to a large deficit is not obviously valid. The plateau is arithmetic. Treat it as arithmetic and the response follows.

Dr_Rosalind_Achebe · Answer

Mechanically, 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.

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.

The relevant detail is that 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.

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.

edited 1 Jun 2026 by Dr_Rosalind_Achebe — removed a claim I could not source

shareimprove this answerflag

answeredDr_Rosalind_Achebe90k15812 May 2026

The distinction between purity and content cannot be repeated often enough here. – vial_five 11 days ago

add a comment

How much protein in grams do I need at 74 kg on 1,400 kcal a day?

protein-intake

nutrition

lean-mass

2 Answers

Protein target arithmetic

PeptideMeter - Independent Peptide Analytics

Your answer

Browse

About

Body mass	1.2 g/kg	1.6 g/kg	2.0 g/kg	Per meal at 1.6 (÷3)
62 kg	74 g	99 g	124 g	33 g
74 kg	89 g	118 g	148 g	39 g
88 kg	106 g	141 g	176 g	47 g
103 kg	124 g	165 g	206 g	55 g
124 kg	149 g	198 g	248 g	66 g