Protein per day for muscle growth: how much on training days

If you train regularly, your protein per day for muscle growth comes to 1.6 to 2.2 grams per kilogram of body weight, and that number is the same on training days and rest days. Going higher added no further muscle in the studies behind it (Morton 2018). What does make a difference is how you spread it across the day.

Where the 1.6 to 2.2 comes from

The clearest figure comes from a meta-analysis of 49 studies with 1,863 participants, all doing resistance training for at least six weeks, some of them with extra protein (Morton 2018). The extra protein increased strength and fat-free mass. Gains in fat-free mass rose up to a total intake of about 1.6 g per kilogram per day and not beyond. The upper end of the confidence interval sat at about 2.2 g/kg, so that's a sensible top end if you want to be sure you're covered. The effect was larger in trained people and smaller in older people (Morton 2018).

The position stands land in the same area. The International Society of Sports Nutrition gives 1.4 to 2.0 g/kg per day for building and keeping muscle with training (Jäger 2017). The American College of Sports Medicine and two dietetics associations name 1.2 to 2.0 g/kg for athletes, spread across the day (Thomas 2016). An older review put it at 1.3 to 1.8 g/kg over three to four meals (Phillips 2011). Both note that the need can rise in phases of energy deficit, and Phillips adds very high training volume as a second reason (Phillips 2011; Thomas 2016).

Protein needs for athletes in endurance sports sit in the same range. In a small study, endurance athletes' protein requirement after a 20 km run averaged about 1.65 g/kg, with a recommended intake derived from it of about 1.8 g/kg, above the classic recommendations for endurance athletes (Kato 2016). So whether you train in the gym or put your kilometers in on the road, you can work with the same protein per kilogram.

Protein on training days and rest days

Every recommendation above is a range per kilogram and day, and the joint position notes that needs move with training, upward after hard sessions (Thomas 2016). In coaching, we treat the day after a hard strength session as part of that session, because the muscle you loaded is still being rebuilt. So your protein per day for muscle growth doesn't drop on a rest day that follows hard work.

What changes on a training day is the carbohydrate. A hard session costs fuel, and in practice the plate grows through rice or potatoes while the protein portion stays put. How to keep an eye on that without weighing every gram is in our piece on macros without counting calories. If two hard sessions fall close together, protein is one part of getting ready for the second, and the rest is in our article on recovery between hard sessions.

Protein distribution across the day

The daily total comes first. After that, the spread. In trained men after a strength session, 80 g of whey over 12 hours produced higher muscle protein synthesis as four servings of 20 g every three hours than as two servings of 40 g or eight of 10 g (Areta 2013).

The ISSN puts a serving at about 0.25 g per kilogram, roughly 20 to 40 g, every three to four hours (Jäger 2017). A review argues the body uses more per meal than the often quoted 20 to 25 g, especially with slowly digested proteins and mixed meals, and suggests about 0.4 g/kg per meal across at least four meals to reach 1.6 g/kg (Schoenfeld 2018). For a 75 kg athlete, that's four meals of around 30 g.

One of those servings can go right before bed. A serving of 30 to 40 g of casein before sleep raised muscle protein synthesis overnight (Jäger 2017). We'd reach for a bowl of cottage cheese or Greek yogurt there, and a shake works too.

The post-workout window is less tight than long assumed (Jäger 2017). Protein in the hours around training still counts, and a meal after the session is usually the easiest serving of the day to place.

Where the protein comes from

Ordinary food gets you there. Dairy, eggs, meat, fish, legumes and tofu all count, and the 1.6 g/kg from the meta-analysis refers to total intake, food and supplements together (Morton 2018). A shake is convenient on days when a meal won't fit. You don't need one.

If you eat fully plant-based, aim at the upper end of the range and mix your sources. Plant proteins carry less leucine, larger servings make up for it, and blends of several sources may help (Jäger 2017). Lentils with rice or tofu with whole grains are easy ways to do both in one meal.

Where counting goes wrong

A familiar pattern: little protein until the evening, then most of the day's total in one big dinner. The daily number may look fine, but the distribution studies point toward about four servings (Areta 2013; Schoenfeld 2018).

Another is treating protein as if it were the calorie target. A hard training day asks for more energy overall, and another shake moves the protein number while the energy gap stays where it was. In our coaching, that extra energy comes from carbohydrate.

Then there's chasing numbers above the range. Beyond about 1.6 g/kg, more protein brought no further gain in fat-free mass (Morton 2018). Going well past 2.2 g/kg buys nothing the meta-analysis could measure, and it takes up room on the plate that carbs and fat could use.