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. A meta-analysis co-authored by Phillips found that gains in lean mass levelled off at about 1.6 g per kg. 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.
On timing: if your daily total is in range, the exact minute after training matters little. The post-workout shake is just one of your protein meals. Spread protein over several meals and don't race the clock.
Two numbers that look like a fight
Stuart Phillips treats about 1.6 g of protein per kg per day as the point where most people stop seeing extra benefit. That can sound low. A 2018 meta-analysis he co-authored (Morton et al.) found that gains in lean mass levelled off at about 1.6 g per kg, with the upper confidence limit near 2.2. 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 argued among the people who study this. The plain version of the daily target, without this debate, is in how much protein.
What the strength curve does
I looked at three papers from 2021 to 2025, and at the conversion from fat-free mass to body weight.
On strength, Tagawa (2022) is the clear picture. Strength gains rose up to about 1.5 g per kg, in people who also lifted. Above that line the curve flattens into a plateau. More protein does not keep buying more strength in a straight line.
One detail worth knowing: a DXA scan does not measure muscle directly. It measures lean mass, which also includes water, organs and connective tissue. So a 2 kg jump in lean mass within a week is mostly water and glycogen, not new muscle.
Where I put the top end
Phillips argues that about 1.6 g per kg covers most people who train. Refalo and Helms think more protein can help in a deficit. Serious researchers still disagree here. 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. If you have kidney disease or reduced kidney function, agree your protein intake with your doctor before going higher. I go up to 2.2 as insurance in two cases.
- Your food log is not precise. In one classic study, dieters who said they could not lose weight underreported their intake by close to half (Lichtman et al. 1992). Protein portions get misjudged too, for example raw versus cooked weight.
- 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.
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 often the weak spot, 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 two cases: a sloppy food log and a hard fat-loss phase.
Does more protein help in a calorie deficit?
The researchers do not agree. Phillips argues that about 1.6 g per kg covers most people who train. Refalo and Helms think more can help in a deficit.
Does strength keep rising as protein goes up?
In Tagawa (2022), strength gains rose up to about 1.5 g per kg in people who lifted. 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) Morton et al. (2018), British Journal of Sports Medicine, DOI: 10.1136/bjsports-2017-097608
5) Lichtman et al. (1992), New England Journal of Medicine, DOI: 10.1056/NEJM199212313272701
Martin Barna
Online nutrition and fitness coach. Since 2013 I have coached 600+ clients.
Apply for coachingThis article is for information only. It is not medical advice. If you have a health condition, talk to your doctor.