Why "Grams Per Kilogram" Is the Right Way to Think About Protein
Protein advice is usually given in one of three ways: a flat number ("eat 100 g a day"), a percentage of calories ("30% protein"), or grams per kilogram of body weight. Only the last one scales properly.
A flat 100 g is far too little for a 100 kg man trying to build muscle and more than enough for a 50 kg woman maintaining her weight. A percentage falls apart during a diet: 30% of 1,300 kcal is under 100 g, which can be too low for a large person cutting calories, precisely when protein matters most.
Grams per kilogram ties the target to the body that needs it. Every serious guideline, from the WHO to sports nutrition bodies, is written this way.
The RDA Is a Floor, Not a Goal
The Recommended Dietary Allowance for protein is 0.8 g per kg of body weight per day. This number is quoted constantly, and it's misunderstood almost as often.
The RDA was set to prevent deficiency in healthy, sedentary adults. It was derived from nitrogen balance studies, which measure the minimum intake at which the body stops losing more protein than it takes in. It says nothing about what optimizes muscle, satiety, body composition or healthy ageing. Researchers who re-analysed the original data using newer methods have argued the true minimum is closer to 1.0–1.2 g/kg even for sedentary adults.
For anyone who trains, diets or is over 60, the evidence points substantially higher.
Protein Per Kg by Goal
| Goal | Protein per kg (body weight) | Notes |
|---|---|---|
| Sedentary adult, maintenance | 0.8 – 1.2 g | RDA is the floor; upper end is more realistic |
| General health, moderately active | 1.2 – 1.6 g | Covers most recreational exercisers |
| Muscle gain (resistance training) | 1.6 – 2.2 g | Gains plateau around 1.6 g/kg on average; higher is a safety margin |
| Fat loss (calorie deficit) | 1.8 – 2.4 g | Higher intake protects muscle when calories are low |
| Fat loss, already lean (under ~15% men / ~25% women) | 2.3 – 3.1 g per kg of lean mass | From studies on physique athletes; near the practical ceiling |
| Endurance athletes | 1.2 – 1.8 g | Supports recovery; more during high-volume blocks |
| Adults over 65 | 1.0 – 1.2 g, up to 1.5 g if active or ill | Counteracts age-related anabolic resistance |
Where these numbers come from
Muscle gain. A 2018 meta-analysis in the British Journal of Sports Medicine (Morton et al.) pooled 49 studies with nearly 1,900 participants and found that protein intake increased muscle and strength gains from resistance training, with the benefit levelling off at around 1.6 g/kg/day. The authors noted the confidence interval extended to about 2.2 g/kg, which is why 1.6–2.2 has become the standard recommendation: 1.6 is the average, 2.2 covers most individuals.
General exercise. The International Society of Sports Nutrition's position stand recommends 1.4–2.0 g/kg for most exercising individuals, and states that higher intakes may be needed to preserve lean mass during calorie restriction.
Fat loss. When calories are low, protein does two jobs: it protects muscle from being broken down for energy, and it's the most filling macronutrient per calorie. A review in the Journal of the International Society of Sports Nutrition (Helms et al., 2014) concluded that lean, resistance-trained people in a deficit benefit from 2.3–3.1 g per kg of fat-free mass, which for most people works out to roughly 1.8–2.4 g per kg of total body weight. The leaner you are, the more protein matters, because the body has less fat to draw on and more incentive to burn muscle.
Older adults. With age, muscle becomes less responsive to protein, a phenomenon called anabolic resistance. The PROT-AGE study group, publishing in the Journal of the American Medical Directors Association (Bauer et al., 2013), recommended 1.0–1.2 g/kg for healthy older adults, rising to 1.2–1.5 g/kg for those who exercise regularly or have acute or chronic illness.
Worked Examples
A 70 kg woman, moderately active, maintaining weight: 70 × 1.4 = 98 g/day
An 85 kg man, lifting four times a week, trying to gain muscle: 85 × 1.8 = 153 g/day (range 136–187 g)
A 95 kg man, lifting, in a 500 kcal deficit to lose fat: 95 × 2.0 = 190 g/day. Note that at 1,900 kcal this is 760 kcal, or 40% of intake. That's high, but it's the correct priority during a cut.
A 60 kg woman, already lean, dieting for a physique goal: Lean mass ≈ 60 × 0.78 = 47 kg. 47 × 2.5 = ~118 g/day, or about 2.0 g per kg of body weight.
A 68 kg active 70-year-old: 68 × 1.3 = 88 g/day
One trap: if you're carrying a lot of body fat, setting protein per kg of total weight can produce very high numbers. A 130 kg person at 2.0 g/kg would get 260 g, more than is useful. In that situation, use your goal weight or lean mass as the basis instead. A 130 kg person aiming for 95 kg can reasonably target 95 × 2.0 = 190 g.
For the full method of setting protein, then fat, then carbs, see our guide to tracking macros.
Does It Matter When You Eat It?
Less than total daily intake, but it isn't irrelevant.
Muscle protein synthesis rises after a protein-containing meal and returns to baseline within a few hours. Spreading intake across the day means more of those stimulus windows. A review by Schoenfeld and Aragon (2018) in the Journal of the International Society of Sports Nutrition suggested a practical target of about 0.4 g/kg per meal across at least four meals to reach the daily 1.6 g/kg, and that the body can use considerably more than the "30 g per meal" ceiling that was once widely repeated.
In practice: three to five meals with a meaningful protein portion in each beats one enormous serving at dinner. The exact timing around training matters far less than most supplement marketing suggests; a protein-rich meal within a couple of hours either side of a session is plenty.
Protein Quality: Does the Source Matter?
Animal proteins (meat, fish, eggs, dairy) contain all the essential amino acids in proportions the body uses efficiently, and they're rich in leucine, the amino acid most responsible for switching on muscle protein synthesis. Most plant proteins are lower in one or more essential amino acids and lower in leucine.
This doesn't make plant-based diets incompatible with high protein targets, but it does mean:
- Vegans and vegetarians generally do well aiming for the upper end of the ranges above
- Combining sources across the day (legumes with grains, soy, seitan, protein powders) covers amino acid gaps
- Soy, pea and mixed plant protein powders perform close to whey in studies when total intake is adequate
Is High Protein Safe?
For healthy adults, yes. A meta-analysis of 28 studies in the Journal of Nutrition (Devries et al., 2018) found no evidence that higher protein intakes harm kidney function in people with healthy kidneys. Intakes up to at least 2.2 g/kg, and in some studies well above 3 g/kg, have been studied without adverse effects.
The exception is people with existing kidney disease, for whom protein intake is a medical matter and should be set with a doctor. Higher protein also means more water is needed, so hydration matters.
Hitting the Number in Real Life
Most people who fall short of their protein target aren't choosing to; they simply don't realise how little protein is in what they eat. A typical breakfast of toast and coffee has around 5 g. A pasta dinner without a defined protein source might have 15 g. Reaching 150 g without planning is very hard.
What helps:
- Anchor each meal on a protein source. Eggs, yogurt or cottage cheese at breakfast; chicken, fish, legumes or tofu at lunch and dinner. Aim for 30–50 g per meal.
- Track for two weeks. Most people are 30–60 g short of where they think they are. Logging closes the gap fast, and it's no longer tedious: photo-based apps like CalSensei estimate protein along with calories from a picture of the plate, which makes it realistic to log mixed dishes and home cooking rather than only packaged food.
- Use dairy and eggs as protein multipliers. Greek yogurt, skyr, cottage cheese and eggs add 15–25 g to almost any meal with little effort.
- Use powder as a supplement, not a foundation. One or two scoops of whey or a plant blend can close a 40–50 g gap; they shouldn't be the main source.
Frequently Asked Questions
How much protein per kg for muscle gain?
Around 1.6–2.2 g per kg of body weight per day. Research shows gains plateau at about 1.6 g/kg on average, with the higher end covering individual variation.
How much protein per kg for weight loss?
Around 1.8–2.4 g per kg of body weight. Higher intakes during a calorie deficit protect muscle and reduce hunger. If you carry a lot of body fat, base the calculation on your goal weight rather than current weight.
Is 0.8 g per kg enough?
It's enough to prevent deficiency in sedentary adults. It's generally not enough to optimise muscle, body composition or healthy ageing, particularly for anyone who exercises or is over 60.
Is 2 g per kg of protein too much?
Not for healthy adults. Intakes of 2 g/kg and higher have been studied extensively without adverse effects on kidney function in people with healthy kidneys.
How much protein should I eat per meal?
Roughly 0.4 g per kg of body weight per meal, spread across three to five meals, is a good practical target. For a 75 kg person that's about 30 g per meal.
Do older adults need more protein?
Yes. Guidelines for adults over 65 recommend 1.0–1.2 g/kg for healthy individuals and 1.2–1.5 g/kg for those who are active or unwell, higher than the standard RDA, to counter age-related muscle loss.
This article is for general educational purposes and is not a substitute for individualized medical or nutritional advice. If you have kidney disease, liver disease, or another condition affecting protein metabolism, consult a qualified healthcare professional before changing your intake.
Sources
- Morton RW, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength. British Journal of Sports Medicine, 2018.
- Jäger R, et al. International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition, 2017.
- Helms ER, Zinn C, Rowlands DS, Brown SR. A systematic review of dietary protein during caloric restriction in resistance trained lean athletes. International Journal of Sport Nutrition and Exercise Metabolism, 2014.
- Bauer J, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. Journal of the American Medical Directors Association, 2013.
- Schoenfeld BJ, Aragon AA. How much protein can the body use in a single meal for muscle-building? Journal of the International Society of Sports Nutrition, 2018.
- Devries MC, et al. Changes in kidney function do not differ between healthy adults consuming higher- compared with lower- or normal-protein diets: a systematic review and meta-analysis. Journal of Nutrition, 2018.
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.
