How much protein in grams do I need at 900 kcal a day?

Scale weight, waist circumference and a repetition maximum, all logged weekly.

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.

Is my approach right even if my number is wrong?

Start with which body weight the target is calculated from, because using total weight in someone with substantial adiposity inflates the number without benefit.

Hydration requirements rise modestly with protein intake because urea excretion increases, which is a real effect and a small one.

Protein target arithmetic

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.

Appetite suppression makes protein-rich foods harder to eat because they are satiating. Liquid protein and leaner, less voluminous sources are the usual practical workaround.

Research-use compounds are not approved for human use, and no supplement substitutes for total intake.

Per-meal saturation is real. One enormous serving does not do the job of three.

edited 28 Jul 2026 by rhian_prydderch — added the citation requested in comments

The underlying point is that protein is also the most satiating macronutrient per kilocalorie, which makes hitting the target easier than it sounds once it is prioritised.

Older adults need more per meal to overcome anabolic resistance, with 1.2 to 1.5 g/kg daily commonly quoted for maintenance and more in a deficit.

A practical construction: 30 to 40 grams at each of three meals plus a 20 to 30 gram snack covers most targets without any protein powder at all.

Stable-isotope feeding studies establish the per-meal saturation of muscle protein synthesis at around 0.4 g/kg in young adults and higher in older ones.

The caveat is that anyone with chronic kidney disease has a genuinely different protein calculation and needs it done by a clinician.

Plant-based patterns need a higher total and more attention per serving.

The short version: total daily protein first, per-meal distribution second, timing a distant third.

The leucine threshold for triggering the response is around two and a half to three grams per meal. Thirty grams of most animal protein reaches it; thirty grams of many plant proteins does not, which is why plant-based targets run higher.

Use reference or adjusted body weight rather than total weight where adiposity is substantial: a common approach is ideal body weight plus a quarter of the excess, which avoids targets that no one could eat.

Leucine threshold effects are documented across protein sources and explain the difference in per-serving requirements between animal and plant proteins.

Plan protein first in the day; with suppressed appetite it will not happen otherwise.

Put another way, this is one of the better-evidenced areas in nutrition and the disagreements are about the top of the range, not the bottom.

Per meal, roughly 0.4 grams per kilogram saturates the synthetic response in most adults, which is about 30 to 40 grams for a typical person. Beyond that the surplus is oxidised or used for other purposes rather than adding to synthesis.

Systematic reviews of high-protein intake in people with normal renal function have not found evidence of harm to kidney function.

1.6 to 2.2 g/kg of reference weight, split three or four ways. That is the answer.

The honest answer is that most people in a deficit fall well short, and closing that gap matters more than any refinement above it.

High protein intakes do not damage healthy kidneys in the published evidence; existing kidney disease is a genuine exception and is a clinical question.

Meta-analytic estimates place the plateau of the dose-response for lean-mass retention with resistance training around 1.6 g/kg, with a confidence interval extending to about 2.2.

Nothing here is dietetic or medical advice.

Healthy kidneys tolerate this fine. Diseased ones are a clinical question.