How much protein do you really need to build muscle: what science says in 2025
Two grams per kilo, 1.5 grams, or more. Protein recommendations for strength training vary enormously depending on the source. Science has a clearer answer than it seems.
Few questions in sports nutrition create as much confusion as how much protein do I need to build muscle. Recommendations range from the 0.8 g/kg of general WHO nutritional guidelines to the 4 g/kg some fitness influencers suggest. Exercise science has a far more precise answer based on decades of clinical research.
The current scientific consensus on protein and muscle
The most complete meta-analysis to date on protein and hypertrophy (Morton et al., 2018, British Journal of Sports Medicine) analysed 49 studies with 1,800 participants. Its conclusions:
- Muscle protein synthesis is optimised at intakes of 1.62 g of protein per kilogram of body weight per day in people training to build muscle.
- Beyond that threshold, the additional effect on muscle gain is marginal or non-existent.
- The practical upper limit of benefit is around 2.2 g/kg/day, a range that covers 97.5 per cent of individuals.
Another meta-analysis (Stokes et al., 2018) confirmed that intakes above 1.62 g/kg produced no additional muscle mass gains in healthy young people doing strength training.
Why do recommendations vary so much?
Differences in protein recommendations have several causes: studies in different populations (young versus older, trained versus beginners, in a surplus versus a deficit), different methodologies for measuring protein synthesis, and - honestly - the commercial interests of the protein supplement industry.
For people over 65, protein synthesis in response to protein intake is less efficient (a phenomenon called anabolic resistance). Recommendations for this group rise to 1.8-2.4 g/kg/day to compensate for that lower efficiency.
Practical ranges by goal:
- Muscle maintenance plus general health: 1.2-1.6 g/kg/day
- Building muscle mass: 1.6-2.2 g/kg/day
- Fat loss with muscle preservation: 2.0-2.6 g/kg/day (a caloric deficit raises the protein requirement)
- Over 65: 1.8-2.4 g/kg/day
Does protein timing matter?
Yes, but less than the supplement industry would like you to believe. Muscle protein synthesis responds to each protein intake relatively independently, provided the dose per serving is sufficient (20-40 g of high-quality complete protein) and total daily intake is adequate.
Spreading protein across 3-5 servings through the day is slightly more efficient than concentrating it in 1-2 large ones, because the amount of amino acids the muscle can use in a single session is limited. However, the practical difference against a suboptimal distribution is modest if total daily intake is correct.
Protein sources: does quality matter?
It does. Complete protein sources (containing all the essential amino acids in adequate proportions) are more efficient at stimulating muscle protein synthesis. Animal sources (meat, fish, eggs, dairy) are generally high-quality complete proteins. Plant sources can be equally effective when combined properly (legumes plus grains, or complete plant sources such as soy, quinoa and edamame).
The most critical amino acid for muscle protein synthesis is leucine. A high-quality protein serving should contain at least 2.5-3 g of leucine to maximise the anabolic response. Whey has a high leucine concentration (around 11 per cent), which partly explains why it is the protein powder with the strongest scientific backing for strength training.
The most common mistake in protein intake
Most people who train for strength do not eat too much protein: they eat too little. General public health recommendations (0.8 g/kg) are designed to prevent deficiency in the general population, not to optimise training adaptation. The gap between 0.8 g/kg and the 1.6 g/kg threshold is the difference between not losing muscle and maximising muscle growth.
Plant versus animal protein for strength training
The question of whether plant protein is equivalent to animal protein for strength training receives increasing attention in the scientific literature. The current answer: plant protein can be just as effective for building muscle, but it requires more attention to total intake and to combining sources.
Plant proteins generally have a lower leucine density than animal proteins and can be deficient in some essential amino acid when taken in isolation. However, combining different plant sources (legumes plus grains, for example) produces a complete amino acid profile. Soy protein, edamame and pea protein have relatively complete amino acid profiles and are solid options for vegetarians and vegans.
An important practical point: people on vegan diets may need slightly higher protein intake (10-15 per cent more) than those consuming animal protein, to compensate for the lower digestibility and lower leucine density of plant sources.
The best protein sources for athletes
Not all proteins are equal. Quality ranking combines digestibility, amino acid profile and leucine concentration (the amino acid that most activates muscle protein synthesis):
Tier 1 (best quality): whey protein: a PDCAAS score of 1.0, high leucine, rapid absorption, ideal post-training. Whole eggs: the reference amino acid profile, high bioavailability, versatile. Casein: a slow protein, ideal before bed. Chicken and turkey: high protein concentration (25-32 g per 100 g), low fat, culinary versatility.
Tier 2 (very good quality): fish (salmon, tuna, cod): high protein, low calories, omega-3 fatty acids. Lean beef: high in zinc and heme iron. Low-fat dairy (Greek yoghurt, cottage cheese).
Tier 3 (good for omnivores, optimal for vegans): soy and its derivatives (tofu, tempeh, edamame): the best plant profile. Legumes combined with grains. Plant protein powder (pea plus rice).
How much protein does the body absorb in a single meal?
The myth of a 30 g maximum per meal has no scientific basis. The gut can absorb practically any amount of protein; what changes is the absorption rate and what the body does with the absorbed amino acids. However, to maximise muscle protein synthesis, the practical threshold is 30-50 g of high-quality protein per meal: above that, the additional amino acids are used mainly as energy substrate or excreted as nitrogen rather than stimulating more protein synthesis.
Practical implication: spread your total protein across 4-5 meals of 30-40 g instead of 2-3 meals of 60-80 g. This maximises muscle protein synthesis across more hours of the day and improves overall satiety.
Protein timing: does it matter?
For overall results, daily distribution matters more than exact timing. However, two moments do have specific evidence: before bed (30-40 g of a slow protein such as casein or cottage cheese improves overnight protein synthesis, especially important for those who train in the hours beforehand) and within the first hour post-training (it boosts the post-exercise anabolic peak, although the real window is 2-3 hours).
A practical daily protein calculator
To simplify the protein target: if you weigh 70 kg and train to build muscle, you need 112-154 g of protein per day (1.6-2.2 g times 70 kg). Spread across 4 meals: 28-38 g per meal. In real food terms: 150 g of cooked chicken breast is 35 g of protein. 200 g of canned tuna is 44 g. Three whole eggs plus 2 whites is 22 g. 300 g of Greek yoghurt (2 per cent fat) is 18 g. 30 g of whey protein powder is 24 g. 200 g of cottage cheese is 24 g. A well-designed diet can hit protein targets without supplements; shakes are a convenient complement when solid food does not cover the daily goal.
Protein in cutting versus bulking phases
In a caloric deficit (cutting): raise protein to 2.2-2.5 g/kg. Higher protein in a deficit not only preserves muscle: it has a higher thermic effect (25-30 per cent of protein calories are spent on its own metabolism, versus 6-8 per cent for carbohydrates and 2-3 per cent for fats) and increases satiety, making the deficit more tolerable. In a caloric surplus (bulking): 1.6-2.0 g/kg is enough. Protein beyond 2.2 g/kg in a surplus has insufficient evidence of additional hypertrophy benefit and simply takes up caloric space that could go to carbohydrates (which improve performance).
Protein for special populations: adjusting intake
Over 50 (sarcopenia): protein needs increase with age. Muscle protein synthesis in response to intake is less efficient (anabolic resistance), so more protein is needed for the same stimulus. Recommendation: 2.0-2.4 g/kg, with special attention to leucine (the threshold leucine dose to activate mTORC1 is higher in older people: around 3-4 g per meal versus 2-3 g in young people, implying protein servings of 35-50 g per meal). Resistance exercise is especially important for combating anabolic resistance.
Endurance athletes: protein is less discussed in running or cycling contexts, but it matters: 1.4-1.8 g/kg for maintaining the muscle used in movement and recovering from the muscle damage caused by training volume. Endurance athletes with a high training load may need 2.0 g/kg in peak volume weeks.
Vegetarians and vegans: the lower quality of plant protein (except soy) and its lower digestibility require a 10-20 per cent increase over standard recommendations. A vegan seeking hypertrophy should aim for 2.0-2.5 g/kg of plant protein, prioritising soy, legumes and tempeh, and supplementing with plant protein powder (pea plus rice) if necessary. Combining plant sources across the day guarantees a complete amino acid profile without needing to combine them in the same meal.
Summary: the key points on protein for muscle
1. Optimal intake: 1.6-2.2 g/kg/day for most strength athletes. 2. Distribution: 4-5 meals of 30-50 g to maximise muscle protein synthesis across more hours. 3. Sources: prioritise high-quality proteins (whey, eggs, lean meats, dairy, soy). 4. Timing: the anabolic window is 2-3 hours, not 30 minutes. 5. In a deficit: raise to 2.0-2.5 g/kg to protect muscle. 6. In a surplus: 1.6-2.0 g/kg is enough. Simple, effective, backed by decades of research.
Where to start
Protein is the most important nutrient for the strength athlete, but optimising it requires no complexity. Hit your daily target spread across 4-5 meals with high-quality sources and you will have done 95 per cent of what protein nutrition can do for your muscular development.
Tools for tracking protein without obsessing
Protein tracking does not have to be daily or lifelong. Use it for 2-3 weeks to calibrate your habitual intake. Many people discover they systematically eat less protein than they think. Once you know the pattern of your usual meals, you can estimate your protein intake without counting apps to within 10-15 per cent, which is enough to optimise results. A practical strategy: identify 5-6 high-protein meals you enjoy and that are easy to prepare. Rotate through them regularly and use protein shakes only to fill the days when logistics do not allow cooking. This 5-6 base meals routine covers protein needs without a daily calculator and with high long-term adherence.
Protein is the nutrient with the greatest impact on strength training results. Optimising it is the nutritional intervention with the highest return on time and attention invested. Make it a non-negotiable priority in your daily diet.
Every gram of protein you consume above your basic needs and within the optimal range is a signal to your body that it can build and maintain muscle. Give that signal consistently and the muscle will respond. Protein is the nutritional variable with the greatest impact on body composition for strength athletes. Prioritise protein at every meal and the rest of your nutrition will fall into place more easily. Protein is the central pillar of sports nutrition.