Protein timing gets far more attention than it earns relative to total daily intake. Total protein explains most of the difference in muscle retention and growth between people. Distribution across meals is a secondary refinement worth a few percent. The post-workout window, as originally described, does not survive controlled testing.
That said, timing is not nothing, and there is one place where it becomes decisive: older adults, whose muscle requires a larger per-meal dose to respond at all. This guide separates the levers by size.
The Verdict
Daily targets by goal and age
The RDA of 0.8 g/kg is a floor set to prevent deficiency in the general population. It is not a performance or healthspan target, and almost every intervention trial in active or older adults uses more.
| Situation | Daily target | Reasoning |
|---|---|---|
| Sedentary adult, weight stable | 0.8 g/kg (0.36 g/lb) | The RDA — a minimum to avoid deficiency, not an optimum |
| Active adult, general health | 1.4–1.6 g/kg (0.64–0.73 g/lb) | The range where muscle-retention benefits plateau in most trials |
| Building muscle in a surplus | 1.6–2.2 g/kg (0.73–1.0 g/lb) | Above roughly 1.6 g/kg the added benefit is small but not zero |
| Losing fat in a calorie deficit | 1.8–2.4 g/kg (0.82–1.1 g/lb) | Higher intake protects lean mass when energy is scarce |
| Adult over 65 | 1.2–1.6 g/kg (0.55–0.73 g/lb) | Anabolic resistance raises the requirement; most older adults eat well under this |
| Chronic kidney disease, stage 3b–5, not on dialysis | 0.6–0.8 g/kg, physician-directed | The one common situation where the standard advice reverses |
Body weight is the usual reference. If body fat is above roughly 30%, lean body mass or goal body weight is a better denominator, otherwise the target inflates without benefit.
The per-meal threshold and why leucine sets it
Muscle protein synthesis is not linear with dose. A single serving stimulates synthesis up to a ceiling, after which additional protein in that meal is oxidized or used elsewhere. The signal that triggers the response is leucine reaching a threshold concentration and activating mTORC1.
| Group | Per-meal protein dose | Leucine needed | Why |
|---|---|---|---|
| Adult under 40 | 0.24 g/kg per meal (~20–25 g) | ~2.5 g leucine | Muscle protein synthesis saturates around here for a single bolus |
| Adult 40–65 | 0.3 g/kg per meal (~25–35 g) | ~2.5–3 g leucine | Response curve starts flattening; slightly more is required |
| Adult over 65 | 0.4 g/kg per meal (~35–45 g) | ~3 g leucine | Anabolic resistance — the same dose produces a smaller response |
| Pre-sleep (any age) | 30–40 g slow-digesting protein | — | Casein or dairy overnight raises overnight synthesis rates |
This is why four meals of 30 g outperform one meal of 120 g, and why the difference is real but modest. It is also why the recommendation changes so much with age.
Leucine content by food source
Two foods with identical protein grams can differ substantially in how much synthesis they trigger. Leucine density is the reason.
| Source | Protein | Leucine | Notes |
|---|---|---|---|
| Whey isolate, 30 g scoop | ~25 g | ~2.7 g | Fastest-absorbing common source; the leucine benchmark |
| Chicken breast, 100 g cooked | ~31 g | ~2.3 g | Highest protein density per calorie of common whole foods |
| Greek yogurt, 200 g | ~20 g | ~2.0 g | Mostly casein — a reasonable pre-sleep option |
| Eggs, 3 large | ~19 g | ~1.6 g | Complete but leucine-light; 4 eggs clears the threshold better |
| Lentils, 1 cup cooked | ~18 g | ~1.3 g | Low in methionine; leucine density lower than animal sources |
| Tofu, 200 g firm | ~20 g | ~1.5 g | Best of the common plant sources on amino acid profile |
| Collagen peptides, 15 g | ~14 g | ~0.4 g | No tryptophan, very low leucine — does not count toward a synthesis dose |
The collagen row is the one worth internalizing. Collagen peptides count as protein on a nutrition label and are close to useless for muscle protein synthesis — they contain no tryptophan and very little leucine. Collagen has real evidence for skin and connective tissue, covered in the collagen guide. It should not be counted toward a daily protein target.
Protein after 60 — where timing stops being optional
Aging muscle shows anabolic resistance: the same protein dose produces a smaller synthetic response. The per-meal requirement roughly doubles, from about 0.24 g/kg in young adults to about 0.4 g/kg after 65. A 70 kg 70-year-old therefore needs around 28 g per meal to get a full response, not 17 g.
Two habits work against this. Appetite falls with age, and older adults commonly eat a very light breakfast and lunch, concentrating protein at dinner. That pattern leaves two of three meals below the threshold, which means two of three meals contribute little to muscle maintenance even when the daily total looks acceptable. Redistributing the same total protein evenly across three meals measurably improves lean mass retention.
Protein alone does not solve it. The synthetic response depends on a mechanical stimulus, so resistance training two to three times weekly is what makes the protein useful. Protein without training preserves less; training without protein plateaus.
Protein inside a fasting window
Compressed eating windows and protein targets pull against each other, and this is where fasting protocols most often fail quietly. An 8-hour window comfortably holds three 40 g servings. A 6-hour window is workable with effort. OMAD is not — nobody reliably eats 130 g of protein in one sitting, and single-bolus absorption favors distribution anyway.
The consequence of missing the target inside a deficit is lean mass loss, lower resting metabolic rate, and weight that returns more easily. If your window and your protein number conflict, widen the window. The protein number is the one doing the work.
What to measure
- Lean body mass — DEXA every 6–12 months is the reliable measure. A consistent bioimpedance scale tracks direction, not absolute values.
- Grip strength — a cheap dynamometer reading correlates strongly with total-body strength and with mortality risk. Below 27 kg in men and 16 kg in women is a recognized sarcopenia threshold.
- Performance markers — the load and reps on two or three main lifts. Rising numbers with stable body weight indicate the protein and training are working.
- eGFR and creatinine — worth a baseline before sustained high intake, and required if kidney disease is known. Note that creatinine rises modestly with higher muscle mass and creatine use, which can look like declining kidney function; cystatin C is the more reliable estimate in that situation.
- Serum urea — rises with protein intake and is a rough adherence check.
Frequently Asked Questions
How much protein do I need per day?
For an active adult, 1.4–1.6 g per kg of body weight (0.64–0.73 g per lb) covers muscle maintenance. In a fat-loss deficit, go to 1.8–2.4 g/kg to protect lean mass. Over 65, aim for 1.2–1.6 g/kg because aging muscle responds less to a given dose. A 82 kg (180 lb) active adult lands at roughly 115–130 g per day.
Is protein timing more important than total daily protein?
No, and the gap is large. Total daily intake explains most of the outcome; distribution is a secondary refinement worth perhaps a few percent. Trials that equalize total protein and vary the timing find small differences. Trials that vary the total find large ones. Hit the daily number first, then distribute it.
Do I need protein right after a workout?
The 30-minute anabolic window does not hold up. Trained muscle stays sensitized to protein for 24 hours or more after a resistance session, and meta-analyses that control for total daily protein find no meaningful advantage to immediate post-workout intake. Getting a 25–40 g serving within a few hours is sufficient. The exception is training fully fasted with the next meal many hours away — there, eating sooner is reasonable.
What is leucine and why does the threshold matter?
Leucine is the amino acid that signals mTORC1 to initiate muscle protein synthesis. Below roughly 2.5 g in a single meal, the signal is weak and the meal contributes little to synthesis even if total protein looks adequate. Whey clears it at 25 g. Lentils need close to 40 g of protein to get there. This is the mechanism behind the per-meal minimum, not an arbitrary number.
Does protein need change with age?
Yes, upward. Older muscle shows anabolic resistance — the same 20 g dose that maximally stimulates synthesis in a 25-year-old produces a blunted response at 70. The per-meal requirement roughly doubles, from about 0.24 g/kg to about 0.4 g/kg. Combined with the appetite decline common after 70, this makes low protein intake one of the biggest modifiable drivers of sarcopenia.
Is high protein bad for your kidneys?
In people with normal kidney function, no. Controlled trials up to 2.5–3.3 g/kg have not shown kidney damage in healthy adults. The picture reverses in established chronic kidney disease: at stage 3b and beyond, guidelines call for restriction to roughly 0.6–0.8 g/kg to slow progression. If your eGFR is under 45, protein targets should come from a nephrologist, not from a training article.
Do plant proteins need different targets?
Yes, modestly. Plant sources are generally lower in leucine and often limited in one essential amino acid — lysine in grains, methionine in legumes. Practically, add 15–25% to per-meal servings and combine sources across the day. Soy, pea protein isolate, and quinoa come closest to animal sources on profile.
Related
- Fasting protocol guide
- Zone 2 cardio guide
- Collagen supplements — why it does not count toward protein targets
- Supplement guides
- Doctor-led longevity programs compared