How much protein do you actually need?
How much protein per kilogram?
It depends on what you are asking your body to do. Losing weight needs the most, because protein is what protects muscle while you are in a deficit.
| Goal | Protein | Why |
|---|---|---|
| Losing weight | 2.0 g/kg | Protects muscle in a deficit |
| Maintaining | 1.6 g/kg | Enough to hold what you have |
| Gaining weight | 1.8 g/kg | Supports new tissue |
| Losing fat while building muscle | 2.2 g/kg | The hardest ask, so the highest |
| Building muscle | 2.0 g/kg | Top of the useful hypertrophy band |
The floor under all of these is about 1.6 g/kg. Below that, muscle retention during weight loss measurably suffers [2].
Is there a point where more protein stops helping?
Yes, and it arrives earlier than most people expect. The meta-analysis on protein and resistance training finds gains flattening out around 1.6 g/kg, with essentially nothing measurable past roughly 2.2 [2]. Anything up to about 2.4 g/kg is harmless and covers every athletic case. Past about 3.2 g/kg there is no added muscle benefit and a rising hydration and kidney load.
There is also a ceiling from the other direction: protein should not exceed 35% of your total calories, the upper bound of the Acceptable Macronutrient Distribution Range [1]. On a small calorie target those two rules collide — and when they do, the muscle-retention floor wins, because under-eating protein while dieting is the worse mistake.
Per kilogram of what, exactly?
This is the part most calculators get wrong. Protein is dosed per kilogram of metabolically active tissue, and fat tissue is not protein-hungry. Multiply grams per kilogram by total bodyweight at a high BMI and the number explodes — it can reach half of a person's daily calories, which is neither necessary nor achievable.
Clinical practice doses on adjusted body weight instead [3]:
AdjBW = IBW + 0.25 × (actual − IBW)
The same grams-per-kilogram numbers are kept — they were validated against lean mass — and simply given the right weight to multiply [4]. Below a BMI of 30 nothing changes. From BMI 30 to 35 the adjustment phases in gradually rather than switching on at a threshold, so gaining a couple of hundred grams never causes a sudden jump in your protein target.
Does a high-protein diet damage your kidneys?
In people with healthy kidneys, there is no good evidence that it does at the intakes above. That is a genuinely different question from whether protein should be restricted in people who already have kidney disease, where a clinician-set limit applies and is often well below 1 g/kg. If you have a diagnosed kidney condition, your protein target is a medical decision, not a fitness one — the numbers on this page do not apply to you.
What about the rest of the plate?
Once protein is set, fat defaults to 25% of calories and carbohydrate takes whatever is left. Fat should not drop below 20% of calories: under roughly that level, absorption of fat-soluble vitamins and sex-hormone production both suffer [1]. Fibre scales with intake at about 14 g per 1,000 kcal.
Carbohydrate is the flexible one on purpose. It is the macro with the fewest hard requirements, so it absorbs the remainder after protein and fat are protected.
How accurate does any of this need to be?
Less than people think. Hitting your protein target within about 10 g most days matters far more than hitting it exactly on any single day, and consistency over weeks beats precision on any one plate. The targets are a range dressed up as a number.
Keep reading
How to split your calories into carbs and fat
Protein first, fat floor, carbs absorb the rest.
Does exercise earn back calories?
Why most calculators count your training twice.
Sources
- Institute of Medicine (NASEM). Dietary Reference Intakes, 2005 — protein RDA and the 10–35% Acceptable Macronutrient Distribution Range.
- 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. Br J Sports Med 2018;52:376–384.
- Dickerson RN. Nutrition support of the obese critically ill patient — dosing on adjusted body weight. Nutr Clin Pract 2017.
- Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm 1974 — the ideal-body-weight formula still used clinically.
- Mifflin MD, et al. Am J Clin Nutr 1990;51:241–247.