How much protein do you need to build muscle?

The short answer

For most healthy adults who lift, about 1.6 g of protein per kilogram of body weight per day is enough to get close to the full muscle-building benefit, and up to about 2.2 g/kg is a reasonable upper target. Daily total matters far more than timing or the exact size of each meal. The evidence for the daily figure is strong; the evidence on distribution, very large meals and protein source is newer and less settled.

What the evidence says

Start with the baseline

Australia's Nutrient Reference Values, set by the NHMRC in 2006, put the Recommended Dietary Intake at 0.84 g/kg per day for men aged 19 to 70 (64 g) and 0.75 g/kg for women (46 g). For adults over 70 it rises to 1.07 g/kg for men (81 g) and 0.94 g/kg for women (57 g) ^[1].

Those numbers are designed to meet the basic needs of nearly all healthy people. They were not designed to maximise the muscle you gain from training.

The daily total for muscle gain

The key paper is a 2018 meta-analysis in the British Journal of Sports Medicine: 49 randomised trials, 1,863 participants, all doing resistance training for at least six weeks. Extra protein increased gains in fat-free mass by an average of 0.30 kg and one-rep-max strength by 2.49 kg. The benefit stopped growing at a total intake of about 1.6 g/kg per day ^[2].

Two details matter. First, the effect is modest. Training drives most of the result and protein adds to it. Second, the benefit was larger in people with training experience and shrank with age ^[2].

The International Society of Sports Nutrition position stand lands in the same neighbourhood: 1.4 to 2.0 g/kg per day for most people who exercise ^[3]. It also suggests more (2.3 to 3.1 g/kg) may help trained people hold on to lean mass while dieting ^[3]. That higher range rests on thinner evidence.

A 2022 meta-analysis of 74 trials reached a similar conclusion by a different route. More protein produced small extra gains in lean mass during resistance training, and the effect was clearest in adults under 65 at 1.6 g/kg per day or more ^[4].

Per meal: a guide, not a ceiling

The old idea that the body can "only use" 20 to 25 g of protein at a time came from short studies of fast-digesting protein eaten alone. A 2018 review argued that this is a threshold, not a cap, and suggested a practical target of about 0.4 g/kg per meal across at least four meals to reach 1.6 g/kg per day, or up to 0.55 g/kg per meal at the 2.2 g/kg upper end ^[5]. The ISSN gives a similar steer: 20 to 40 g per serve, spread every three to four hours ^[3].

Timing: the window is wide

A meta-analysis of protein timing found that once total daily protein was accounted for, eating protein close to training made no significant difference to strength or muscle size. Total intake was the strongest predictor of growth ^[7].

Older adults

Ageing muscle responds less strongly to protein. In the 2018 meta-analysis the benefit of supplementation declined with age ^[2]. In the 2022 analysis, adults 65 and over who trained saw lean-mass benefits at 1.2 to 1.59 g/kg per day ^[4]. Both figures sit well above the NHMRC intakes for over-70s ^[1].

Plant versus animal

A meta-analysis of 16 randomised trials found protein source did not change gains in absolute lean mass or strength overall. Animal protein had a small edge for lean mass in adults under 50, of about 0.41 kg ^[8].

When the total is high enough, the gap seems to close. In a 12-week trial, 19 habitual vegans and 19 omnivores trained twice a week with protein set at 1.6 g/kg per day. Muscle and strength gains did not differ ^[9]. These were untrained young men, and the vegan group used soy protein isolate to reach the target.

Healthy kidneys

A meta-analysis of 28 trials and 1,358 adults without kidney disease compared higher-protein diets (1.5 g/kg or more, or at least 100 g a day) with lower intakes. Changes in kidney filtration rate did not differ, and the authors concluded higher intakes do not harm kidney function in healthy adults ^[10]. This does not apply to people with existing kidney disease, and the included trials accepted durations as short as five days, so very long-term data are thinner.

What is still uncertain

• Whether more than 1.6 g/kg helps. The average benefit plateaus there, but the estimate has a wide margin, which is why reviews quote an upper target of 2.2 g/kg ^[5].
• How much distribution matters. Even spreading makes sense on paper. The 100 g study challenges how strict it needs to be, but it is a single acute trial ^[6].
• Women and older lifters. Much of the per-meal and source research is in young men ^{[6] [9]}.
• Whole-food plant diets. The vegan trial relied on a soy supplement ^[9]. Reaching the same total from legumes and grains alone is less tested.

What it means in practice

Work out your number first. At 1.6 g/kg, a 60 kg person needs about 96 g a day and a 75 kg person about 120 g. Split over four meals, that is roughly 25 to 30 g each. Three bigger meals also works.

Approximate protein in common foods, from Australian Food Composition Database figures compiled by Foodwatch:

• Beef fillet steak, cooked, 150 g: 40 g
• Chicken, half a breast, cooked, 150 g: 34 g
• Fish fillet, cooked, 120 g: 32 g
• Canned tuna or salmon, drained, 100 g: 25 g
• Tofu, 100 g: 13 g
• Two medium eggs: 12 g
• Yoghurt, 200 g tub: 10 g
• Almonds, 50 g: 10 g
• Milk, 200 mL glass: 7 g
• Cheddar, 30 g slice: 7 g
• Lentils or chickpeas, half a cup cooked (75 g): 6 g

Check labels, because products vary.

A few working rules:

1. Hit the daily total. It is the factor with the strongest evidence.
2. Put a solid protein serve in each main meal. Do not stress about the clock around training.
3. Eating mostly plants? Aim for the same total and use a mix of soy, legumes, grains and nuts. You will need larger serves.
4. Over 65? Baseline needs are higher, and intakes of 1.2 g/kg or more alongside resistance training are supported.
5. Have kidney disease or another medical condition? Talk to your doctor or an accredited practising dietitian before raising protein.

This is general information for healthy adults who train. It is not personal medical advice.