Protein for Muscle Gain: 1.6 g/kg (Morton 2018)

Protein is the most-written-about macronutrient on the fitness internet and simultaneously the one with the cleanest meta-analytic evidence base. This article pulls the important numbers out of the 2013–2023 literature and turns them into daily and per-meal targets.

The Morton 2018 meta-analysis

Morton and colleagues at McMaster pooled 49 studies (n=1,863) measuring protein supplementation's effect on lean mass gains alongside resistance training.^[1] Protein supplementation added lean mass (0.30 kg on average) and strength, and a break-point analysis of total daily intake against fat-free-mass gain produced the plateau most guidance now uses:

Daily protein intake for lifters — Morton et al. 2018

Below 1.0 g/kg    Insufficient for hypertrophy outcomes
1.0 – 1.6 g/kg    Dose-response region — more is better
1.62 g/kg         Break point — additional protein stops adding lean mass
2.2 g/kg          Upper end of its 95% confidence interval
Above 2.2 g/kg    No harm documented, but no added lean mass either

Two caveats about this plateau:

1. It's a group-average break point with a wide interval (up to about 2.2 g/kg), so 1.6 g/kg is the point estimate, not a guarantee for every lifter. The same analysis found supplementation helped less with increasing age and more in trained lifters.^[1]
2. It was fitted on body-mass, not lean-mass. For a lean lifter, 1.6 g/kg body mass and 1.8 g/kg lean mass are similar. For a very overweight lifter, they diverge and lean-mass scaling is more honest.

Dieting lifters need more

Helms, Aragon, and Fitschen's 2014 bodybuilding-contest review^[3] synthesised the literature on protein requirements during energy restriction. Their conclusion: 2.3–3.1 g per kilogram of fat-free mass preserves more lean mass than Morton's 1.6 g/kg does when the lifter is in a calorie deficit, particularly when the deficit is aggressive or the lifter is already lean. The same higher-protein-plus-lifting defence applies to rapid medical weight loss, covered in GLP-1 muscle loss and how to keep lean mass.

The practical difference is about 25–40 additional grams of protein per day during a cut for most lifters. For someone with 65 kg of lean mass:

• Maintenance / slight surplus: 1.6 g/kg body mass, roughly 135 g/day for an 85-kg lifter.
• Aggressive deficit: 2.5 g/kg fat-free mass, roughly 163 g/day for the same lifter with 65 kg FFM.

The Protein Intake Calculator turns this into a range: it asks for body weight, activity level, goal (maintain, bulk or cut) and meals per day, and returns a daily target and a per-meal dose. For an athlete in a cut its range is 2.0–2.6 g/kg of body weight, Helms's range for a lifter at about 15% body fat.

Per-meal distribution: what we thought, what we think now

The 2010s guidance was built on short tracer studies of muscle protein synthesis (MPS) after a single dose. In young men MPS stopped rising at about 0.24 g/kg of body mass per meal; in older men it took about 0.40 g/kg.^[9] The ISSN's 2017 position stand turned this into 0.25 g/kg, or 20–40 g, per meal, spread across the day.^[2]

Macnaughton et al. 2016^[5] showed that 40 g of whey produced a bigger MPS response than 20 g after a whole-body resistance workout, against the 20–25 g then accepted as the maximum. Trommelen et al. 2023^[6] went further: 100 g of milk protein in one dose produced a larger and longer anabolic response than 25 g, still running after 12 hours, with almost no extra amino-acid oxidation.

What this means practically:

• If you can easily fit four feedings at 30–40 g each, do it. You'll accumulate MPS bouts cleanly across the day.
• If intermittent-fasting or a one-meal schedule suits you, you're not sacrificing lean-mass outcomes that we can reliably detect — just push the per-meal dose up to 60–100 g.
• Ignore the “you can only absorb 30 g” claim. Absorption was never the limit; the studies measured how much muscle protein synthesis one dose produces.

Protein quality and leucine

Leucine is the amino acid that switches on muscle protein synthesis, which is why protein sources are compared on it. The 2017 ISSN position stand recommends that each dose contain 700–3,000 mg of leucine alongside the other essential amino acids.^[2]

Gorissen and colleagues measured the amino-acid content of fifteen commercial protein isolates and worked out how much of each it takes to deliver the 2.7 g of leucine in 25 g of whey:^[10]

Protein needed to match the leucine in 25 g of whey (Gorissen et al. 2018, Table 2)

Source        Protein (g)
──────────────────────────
Corn               20
Whey               25
Caseinate          30
Milk               31
Potato             33
Casein             34
Brown rice         37
Pea                38
Egg                39
Soy                40
Wheat              45
Oat                47
Microalgae         48
Lupin              52
Hemp               54

For lifters, the practical rule is: hit a sensible per-meal dose (30–40 g) from a mixed source and leucine will take care of itself. A meal built on a single plant protein needs roughly 40 g of it to match 25 g of whey; blending sources (pea with rice, or plant with dairy) gets there with less.^[10]

Practical high-protein meal patterns

Bulking-phase athlete (about 200 g/day)

07:00  Breakfast   Oats + 250 g Greek yogurt + whey 25 g     45 g
11:00  Snack       Apple + 40 g whey + almonds               38 g
14:00  Lunch       Chicken 180 g + rice + veg + olive oil    52 g
18:00  Pre-train   Banana + 25 g whey                         22 g
21:00  Dinner      Salmon 200 g + sweet potato + salad        45 g
                                                     Total  202 g

Cutting-phase athlete (about 200 g/day, lower calories)

08:00  Breakfast   Egg whites 6 + 2 whole eggs + spinach     40 g
12:00  Lunch       Chicken breast 220 g + veg + salsa        68 g
16:00  Snack       Tuna 150 g + rice cakes                    42 g
20:00  Dinner      Lean beef 180 g + broccoli + tomato       55 g
                                                     Total  205 g

Vegan lifter (about 200 g/day)

08:00  Breakfast   Tofu scramble 250 g + oats + pea protein 40 g  62 g
13:00  Lunch       Tempeh 180 g + quinoa + veg + tahini          48 g
17:00  Snack       Pea + rice blend protein 50 g                  40 g
21:00  Dinner      Seitan 150 g + lentil stew + rice             55 g
                                                           Total 205 g

Vegan patterns need larger per-meal portions for the same leucine: each meal above carries 40 g or more of protein, with pea and rice blended in the shakes.^[10]

Pre- and post-workout timing

The “anabolic window” of the 2000s has not survived the review literature. Schoenfeld, Aragon and Krieger's meta-analysis of 23 hypertrophy studies found no effect of protein timing once total protein intake was accounted for; total intake was the strongest predictor of muscle gain.^[8]

Two defensible timing claims remain:

• Get a protein dose within a few hours on either side of training. With meals every four hours or so, that happens without planning.
• If you trained fasted, consume protein shortly after. This is more about starting recovery than about a magic window.

What doesn't hold up: “You must drink whey within 30 minutes of racking the bar or you lose gains.” The timing meta-analysis found no such effect once total protein was matched.^[8]

Protein across the day — worked example

An 82-kg intermediate lifter in a slight surplus, targeting 1.8 g/kg = 148 g protein/day:

Breakfast       Greek yogurt 200 g + oats + whey 20 g    ≈ 35 g
Lunch           Chicken 150 g + rice + veg               ≈ 45 g
Pre-train       Whey 25 g                                 ≈ 25 g
Dinner          Salmon 160 g + potatoes + salad          ≈ 40 g
                                                    Total  145 g

For the same lifter running a cut, push to ~180 g/day by adding an extra whey dose or increasing the main-meal portions. The Macro Calculator and TDEE Calculator together give you the calorie scaffolding to fit protein into without accidentally over-eating.

Safety, high intake, and kidneys

The ceiling beyond which protein intake becomes counterproductive in healthy lifters has not been identified in the literature. Doses north of 3 g/kg have not produced measurable lean-mass benefit over 1.6–2.2 g/kg, so there's a practical-not-safety ceiling: more is wasted, not harmful.

• Aim for 1.6 g/kg/day in a bulk, 2.3–3.1 g/kg fat-free mass in a cut.
• Distribute over 3–5 meals at 30–40 g each; one-meal schedules aren't disqualifying.
• Leucine is the switch — hit the threshold and total protein does the rest.
• “Anabolic window” is much wider than we were told in 2005.
• Above 2.2 g/kg there's no documented benefit in Morton's dataset, and no documented harm either.

Tools: Protein Intake Calculator, Macro Calculator, TDEE Calculator.

Population boundaries of the main meta-analyses

The dose-response evidence underpinning 1.6 g/kg and the cut-phase 2.3–3.1 g/kg targets was generated in specific populations. Honest application means knowing where those results extrapolate and where they don't:

• Morton et al. 2018 — sample. 49 randomised trials, 1,863 healthy adults, at least six weeks of resistance training each^[1]. The benefit of extra protein shrank with age and was larger in trained lifters, so the 1.6 g/kg point estimate fits trained young and middle-aged lifters best.
• Helms et al. 2014 — sample. Review narrative specifically on natural bodybuilders in contest prep^[3]. The 2.3–3.1 g/kg FFM recommendation applies specifically to contest-lean lifters in active caloric deficits; extrapolating to non-lifting populations in cuts (e.g. general weight loss) is not what the paper supports.
• Macnaughton 2016 — sample. 30 resistance-trained young men, each tested with 20 g and 40 g of whey^[5]. Older adults need more per meal for the same response: about 0.40 g/kg of body mass against 0.24 g/kg in young men (0.60 against 0.25 g/kg of lean mass).^[9]
• Trommelen 2023 — sample. 36 healthy, recreationally active young men given 0, 25 or 100 g of milk protein after exercise^[6]. The finding that a large dose is not wasted is solid within that sample; how it carries over to women and older adults is untested.
• Who was studied. The three per-meal studies above recruited only men. Morton's meta-analysis included women, but most of the per-meal guidance is inferred from male samples.
• No validated data for pregnancy, lactation, paediatrics, or clinical renal populations. For these groups, the 1.6 g/kg default does not apply; specialist guidance from a registered dietitian replaces this article's recommendations entirely.

Alternative-view framing: dose vs distribution vs total

Three schools of thought on what drives muscle-protein synthesis at the daily level:

• Total daily dose dominates. Schoenfeld, Aragon, and others argue that once total daily protein is adequate (~1.6 g/kg), per-meal timing and frequency matter very little. Supported by Morton's daily-dose regression^[1]. Practical implication: hit the daily total; don't stress about distribution.
• Each meal should reach the dose that maximises MPS. The acute tracer studies define one: about 0.24 g/kg in young men and 0.40 g/kg in older men,^[9] or 40 g of whey after whole-body training.^[5] Practical implication: 3–5 meals that each reach it, not two mega-doses.
• A large dose is not wasted. Trommelen 2023^[6] found no upper limit in the size or length of the anabolic response to one post-exercise meal over 12 hours, loosening the per-meal story. Total intake and the training stimulus dominate.

The honest practical answer: all three are defensible and the evidence supports pragmatic distribution — hit your daily total, try to clear the leucine threshold at 3+ feedings, don't agonise over missing one feeding by 30 minutes or over a single 60 g mega-meal. The outcome difference between an optimally distributed 160 g day and a lumpily-distributed 160 g day is small.

Common failure modes

• Targeting the Morton 1.6 g/kg ceiling during a deep cut. The cutting-phase Helms recommendation is 2.3–3.1 g/kg FFM, which for a lifter at 12% body fat is 2.0–2.7 g/kg bodyweight. Sticking with 1.6 g/kg during an aggressive deficit under-protects lean mass — the fix is trivial and the cost of under-eating protein in a cut is large.
• Assuming one 80 g dinner covers a day. Older adults need a larger dose per meal for the same response (about 0.40 g/kg against 0.24 g/kg in young men),^[9] so for them a day's protein packed into one or two meals leaves fewer meals that reach it.
• Collagen or BCAA supplements counted toward daily total. Collagen contains no tryptophan and little leucine, so it is not a complete protein; BCAAs are three amino acids, not protein. Count them separately from the daily total, not toward it.
• Vegan protein doses matched one-to-one with animal. Soy, pea and brown-rice protein need 37–40 g to match the leucine in 25 g of whey.^[10] A vegan lifter planning meals gram for gram from whey-based advice under-doses leucine per meal; raise the portion or blend sources.
• Dropping protein first when calories are cut. Protein has the highest satiety effect and the strongest muscle-protective role in a deficit. Cut fat or carbs; keep protein high. Exactly inverted, as Helms 2014^[3] and many cut-phase studies consistently show, relative to what "save calories" intuition suggests.

Protein pacing for morning vs evening trainers

Training time shifts practical protein distribution strategy:

• Early-morning trainer, fasted. The last meal was the night before, so eat protein soon after the session; this is the one case where the timing advice still has teeth. Trommelen 2023^[6] means a larger breakfast dose (40–50 g) is not wasted.
• Mid-day trainer. Lunch before and dinner after cover the session; a normal 4–5 meal day needs no adjustment.
• Evening trainer. Dinner after training, then 30–40 g of casein before sleep, which the ISSN position stand reports raises overnight muscle protein synthesis.^[2]