People ask whether the shake has to land the minute the last set ends. The studies in this piece answer the question that decides more: how much protein you eat across the day.
Short answer: I use 1.6 to 2.2 g of protein per kg of total body weight. The low end is where the papers agree. Phillips says 1.6 g per kg covers 97 to 98% of people. Refalo's lower edge, once you convert it off fat-free mass, lands near 1.4 to 1.6 g per kg for a typical lifter. The top end is still argued.
Two numbers that look like a fight
Stuart Phillips has said that 1.6 g of protein per kg per day is the ceiling. A lot of people hear that as too low. Refalo and Helms (2025) go higher, to 1.9 to 3.2 g per kg, but they count that on fat-free mass, not on the weight you see on the scale.
Convert that fat-free mass back to total body weight for a typical person in the gym, at about 18 to 28% body fat, and Refalo's lower edge comes out near 1.4 to 1.6 g per kg of body weight. That is where the two numbers meet.
They split at the top. And the top is still a live argument among the people who study this. It is not closed. The plain version of the daily target, without this debate, is in how much protein.
What the strength curve does
I looked at three meta-analyses from 2021 to 2025, and at the arithmetic most posts skip.
On strength, Tagawa (2022) is the clear picture. Up to 1.5 g per kg it climbs nicely. Above that line the curve flattens into a plateau. More protein does not keep buying more strength in a straight line.
One detail people skip: a DXA scan does not measure muscle. It measures lean mass. Of that, actual muscle tissue is only 35 to 65%. So when someone cheers "+2 kg of muscle" after a week, half of it can easily be water.
Where I put the top end
Phillips says 1.6 g per kg is enough even in a deficit and with hard training, and that above that the amino acids are burned more for energy. Refalo and Helms think more protein can help in a deficit. That is a live debate between serious researchers, not a settled fact. Keeping muscle while calories are down is in build muscle in a calorie deficit.
How I use it: 1.6 to 2.2 g per kg of total body weight. Agreement sits on the low end. I go up to 2.2 as insurance in three cases.
- Your food log is not precise. The error is often 20 to 50% (Lichtman 1992).
- You are in a hard fat-loss phase, where the debate is still open. The size of the deficit itself is in calorie deficit: how much to eat.
- You are a woman. In a sub-analysis from Refalo's group, women may sit nearer the lower end, so the insurance is there if the log is rough.
Protein is not the first lever
Do not fuss over protein until training, calories and sleep are in place. Without those, protein is an expensive insurance policy. Sleep is the one people skip, and the numbers are in how much sleep do you need.
Frequently asked questions
Why do Refalo and Helms say 1.9 to 3.2 g per kg?
That range is per kg of fat-free mass, not of scale weight. For a typical lifter at 18 to 28% body fat, the lower edge converts to about 1.4 to 1.6 g per kg of body weight. That meets Phillips. The gap that remains is the top end.
When does 2.2 g per kg make sense?
As insurance in three cases: a sloppy food log (the error is often 20 to 50%), a hard fat-loss phase, and women, who in Refalo's sub-analysis may sit nearer the lower end.
Does more protein help in a calorie deficit?
The researchers do not agree. Phillips says 1.6 g per kg is enough even in a deficit and with hard training. Refalo and Helms think more can help in a deficit.
Does strength keep rising as protein goes up?
In Tagawa (2022), strength climbs nicely up to 1.5 g per kg. Above that the curve flattens.
Is protein the most important thing?
No. Do not fuss over it until training, calories and sleep are handled. Without those it is an expensive insurance policy.
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Apply for coaching Get the free Fat Loss KitSources, so you can check:
1) Tagawa et al. (2021), Nutrition Reviews, DOI: 10.1093/nutrit/nuaa104
2) Tagawa et al. (2022), Sports Med Open, DOI: 10.1186/s40798-022-00508-w
3) Refalo, Trexler and Helms (2025), Strength and Conditioning Journal, DOI: 10.1519/SSC.0000000000000888
4) Phillips, McMaster News (2026), as named in the source article
5) Lichtman 1992, named in the source for a food-record error often of 20 to 50%. No journal or DOI printed there.
Martin Barna
Online nutrition and fitness coach. Since 2013 I have helped 600+ people lose fat and keep the result. Science, not crash diets.
Apply for coachingThis article is for information only. It is not medical advice. If you have a health condition, talk to your doctor.