The range the professional society settles on
In its position stand on protein and exercise, the International Society of Sports Nutrition gives 1.4 to 2.0 grams per kilogram of body weight per day as sufficient for most people who exercise. Not per meal, not per training day – per day and per kilogram.
At 65 kilograms that is 91 to 130 grams. The range isn't a dodge: people who train a lot and heavy tend towards the top, those who train moderately towards the bottom. Both ends are supported by evidence; neither is the only right one.
The catch: the research was done mostly on men
The ISSN's position stand on the nutrition of female athletes points this out directly: much of the sports nutrition research was carried out with male participants, and the results were then transferred. Where recommendations for women differ, this is often based on a narrower evidence base than the number suggests.
That's no reason to discard the recommendation. It is a reason to read it as guidance rather than a law of nature.
What Rhythmus calculates with
Since version 1.6, the app uses the reference values of the German Nutrition Society (DGE): 0.8 g per kilogram of body weight, 1.0 g from age 65. If your BMI is above 25, it uses the weight that would correspond to a BMI of 25, because the reference values refer to normal weight.
The app shows the ISSN range alongside as a note for anyone who strength trains regularly. We don't set it as a target: it applies to athletes, and its evidence base in women is narrow, see above.
The calorie target next to it comes from the Mifflin-St Jeor equation, the most widely used estimate of basal metabolic rate, multiplied by an activity factor based on your training details. That's an estimate too: in its original study the equation explained about 71 percent of the variation – so for roughly three in ten people it is noticeably off.
Two misunderstandings
- “Per kilogram” means body weight, not muscle mass. Some recommendations refer to fat-free mass; then the numbers are different. Mixing the two gives you a much too high requirement.
- More isn't better. Above the range, no additional benefit for muscle growth has been shown. The excess protein is metabolised like any other energy.
In practice
Spreading the amount across the day is easier than packing it into one meal. Rhythmus suggests three meals and scales the amounts to your target – omnivore, vegetarian or vegan. On a plant-based diet it's worth looking at combinations: pulses and grains complement each other's amino acid profiles better than either alone.