Protein is everywhere right now. Protein bars, protein coffee, protein pancakes.
So it’s fair to ask: how much do you actually need?
The research gives a clear answer for most people. It also gives a ceiling, and a reminder that protein isn’t the main event.
- The official minimum for adults is 0.8 grams of protein per kilogram of body weight a day.
- In a review of 49 trials, extra protein stopped adding muscle at about 1.6 grams per kilogram a day.
- Weight training did most of the work. Protein added a small extra on top.
How much protein do I need?
For most healthy adults, the minimum is 0.8 grams per kilogram of body weight a day. That’s about 0.36 grams per pound.
That’s the US Recommended Dietary Allowance (RDA). The World Health Organization (WHO) report sets a very similar safe level: 0.83 grams per kilogram for all adults.
But the minimum isn’t the whole story. If you lift weights, the research points higher, to about 1.6 grams per kilogram.
Older adults may also need more. Some experts suggest 1.0 to 1.3 grams per kilogram, especially with strength exercise.
Here’s what those numbers mean in grams a day:
| Body weight | Minimum (0.8 g/kg) | Older adults (1.2 g/kg) | If you lift weights (1.6 g/kg) |
|---|---|---|---|
| 60 kg (132 lb) | 48 g | 72 g | 96 g |
| 70 kg (154 lb) | 56 g | 84 g | 112 g |
| 80 kg (176 lb) | 64 g | 96 g | 128 g |
| 90 kg (198 lb) | 72 g | 108 g | 144 g |
For a sense of scale, the MedlinePlus guide to protein says one ounce of most protein foods gives about 7 grams.
That ounce could be 30 grams of meat or fish, one large egg, or half a cup of cooked beans or lentils.
What the research shows
The biggest review of protein and strength training
The main study is a 2018 review in the British Journal of Sports Medicine. It pooled 49 randomised trials with 1,863 people.
In every trial, people did weight training for at least 6 weeks. Some also took extra protein, and some didn’t.
That design matters. Because people were randomly assigned, the trials can show what protein itself adds.
Protein helped. People who took it gained more strength and more lean mass, which is mostly muscle.
Gains stopped at about 1.6 grams
The researchers then asked a sharper question: at what total daily intake do the gains stop growing?
Their answer was 1.62 grams per kilogram a day. Above that, extra protein added no more lean mass.
There’s a catch, and I want to be upfront about it. The range around that number was wide, from 1.03 to 2.20 grams.
The turning point also wasn’t statistically certain. So 1.6 is a good estimate, not a hard line.
For people trying to build as much muscle as possible, the authors suggest going up to about 2.2 grams to be safe.
Weight training did most of the work
This is the part I find most useful. Protein helped, but the training itself mattered far more.
| What was measured | From weight training alone | Extra from protein |
|---|---|---|
| Strength (heaviest single lift) | 27 kg gained on average | 2.49 kg more (about 9%) |
| Lean mass | 1.1 kg gained on average | 0.30 kg more (about 27%) |
The authors put it plainly. Training was “the much more potent stimulus”.
So if your goal is to get stronger, the workout is the big lever. Protein is the helper.
Most adults need at least 0.8 grams of protein per kilogram a day. With weight training, gains levelled off at about 1.6 grams.
Who gained the most from extra protein
The extra protein helped some people much more than others.
| Group | Extra lean mass from protein |
|---|---|
| People already used to weight training | 1.05 kg |
| Beginners | 0.15 kg |
| Under 45 | 0.55 kg |
| Over 45 | 0.06 kg |
The effect also got smaller with age. But only 13 of the trials included people over 45, so this part is less certain.
Who funded it
The senior author, Stuart Phillips, thanked Canadian government research funds for support. He has also received grants and fees from the US National Dairy Council.
In 2020, the journal added a correction: another author, Brad Schoenfeld, advises a sports supplement company.
The results themselves were not changed.
The newest research
A 2022 review of 74 trials agreed
A 2022 review in the Journal of Cachexia, Sarcopenia and Muscle pooled 74 randomised trials in healthy adults.
Overall, extra protein added about 0.5 to 0.7 kg more lean mass than in the comparison groups. The effect was the same in trials with strength training.
The amount that worked depended on age. Under 65, the gains showed up at 1.6 grams per kilogram or more.
At 65 and over, they showed up at 1.2 to 1.59 grams. But that result depended mostly on one large study.
Without exercise, extra protein made no clear difference to lean mass. Only 6 trials tested that, though.
This review was funded by a grant from ILSI Europe, a science group funded by food companies. Stuart Phillips was an author here too.
Is a high-protein diet bad for your kidneys?
This is a common worry. A 2018 review in The Journal of Nutrition looked at 28 trials with 1,358 adults without kidney disease.
The higher-protein groups ate about 1.81 grams per kilogram a day. The comparison groups ate about 0.93 grams.
The change in kidney filtering didn’t differ between the groups. The authors concluded higher protein didn’t harm kidney function in healthy adults.
Two cautions. The trials lasted from about a week to two years, and the authors rated the evidence quality as low to very low.
And none of this applies to people who already have kidney disease. They should follow their doctor’s advice.
The WHO report found no safe upper limit for protein. But for people at risk of kidney stones, it advises staying under 1.4 grams per kilogram a day.
What earlier research found
Why 0.8 grams is a minimum, not a target
A 2017 review in Advances in Nutrition explained where the 0.8 number comes from. It has barely changed in over 70 years.
It was set as the least protein people need to avoid losing it from the body. It was never meant as the best amount.
The same review points to a wider US range. Protein can make up 10% to 35% of your daily calories.
Older adults may need more
A 2015 review in Nutrients looked at protein needs as we age.
It found consistent evidence that 1.0 to 1.3 grams per kilogram a day, plus strength exercise twice a week, helps limit muscle loss with age.
The source of protein may matter for long life
A 2020 study in the European Journal of Epidemiology combined 11 long-term studies of 350,452 people.
People who ate the most protein had a 5% higher risk of death than those who ate the least. This was mostly linked to animal protein.
People who ate the most plant protein had a 7% lower risk of death. These are links from observational studies, not proof.
We’ve also looked at whether eggs are bad for cholesterol, one of the most common protein foods.
How it fits together
Two large reviews of trials agree. Extra protein adds a small amount of muscle during strength training, with gains levelling off around 1.6 grams.
How much should you trust this?
Promising. The minimum is solid, and the trials agree that protein helps a little. The exact best amount is still an estimate.
What makes it convincing
- The muscle findings come from randomised trials, not just surveys.
- Two separate reviews, of 49 and 74 trials, point the same way.
- The minimum is backed by both US and WHO expert reports.
What makes me cautious
- The 1.6-gram turning point had a wide range and wasn’t statistically certain.
- Few trials included older adults.
- One researcher co-wrote all three main reviews and has dairy and beef industry ties.
- The kidney trials lasted two years at most, and their quality was rated low.
| The evidence shows | The evidence does not show |
|---|---|
| 0.8 g per kg is enough to avoid losing protein | That 0.8 g is the best amount for everyone |
| Extra protein adds a little muscle with weight training | That protein builds much muscle without exercise |
| Gains levelled off around 1.6 g per kg | An exact cut-off that fits every person |
| No kidney harm in healthy adults in trials of up to two years | Safety for people with kidney disease |
What this means for you
- Know your minimum. Multiply your weight in kilograms by 0.8. That’s your daily floor in grams.
- Lifting weights? Aim higher. About 1.6 grams per kilogram covers most people. Going beyond that added no more muscle on average.
- Over 65? Consider 1.0 to 1.3 grams per kilogram, together with strength exercise.
- Train first. The workout did far more than the protein did.
- Have kidney disease? Ask your doctor before eating more protein.
In this interview on the ZOE podcast, Stuart Phillips, the senior author of the main review, talks about how much protein people need:
What we still don’t know
- What’s the best amount for older adults? Too few trials have tested it.
- Does the source matter for muscle? Most trials used animal protein, such as whey or milk.
- Is more protein safe for decades? The kidney trials lasted two years at most.
- Does protein help without exercise? The few trials that tested it found no clear benefit.
My take: train first, then eat enough
What I like about this research is how practical it is. It gives a floor, a ceiling and a priority.
I’m less convinced by the idea that you need huge amounts. For most people, gains levelled off well before protein-shake marketing would suggest.
So my reading is simple. Eat at least 0.8 grams per kilogram.
If you lift, aim for about 1.6. And don’t skip the workout.
Last reviewed: 2026-10-13
Covers: How much protein adults need, protein and muscle gain with strength training, protein needs in older adults, high protein and kidney function
Evidence: Promising — the minimum is well established; trials agree extra protein adds a little muscle with training, but the best amount is an estimate
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