Protein Needs Based on Fat-Free Mass?

Today we’ve got a question on protein needs, from Stefan in Sweden. He writes:

“If I understand correctly, protein intake is often mentioned in terms of grams of protein per kilo of bodyweight, for instance 2 grams per kilo. Wouldn’t fat-free mass be a more relevant metric, since a person at 80 kilos would have a very different muscle mass if he is at 5% body fat vs. 40%.”

I answer this question in the video below, but if you’d rather read, you can skip to the transcript below the video.

Stefan, you’re absolutely correct that fat-free mass is probably a more relevant predictor for protein need than total bodyweight is. Protein is used for thousands of different purposes in the body, by a variety of different organs. Fat mass, however, isn’t very metabolically active, so it doesn’t really affect our protein need too much. Our fat-free mass on the other hand, which is everything in our bodies that isn’t fat, is generally much more metabolically active. Our muscle mass is included in the fat-free mass, and a larger muscle mass requires a higher protein intake.

So it makes sense to take into account how much fat-free mass you have when trying to calculate your protein needs. The problem is that most relevant research on protein intake only gives us recommendations based on total bodyweight. That is: in studies on protein intake, fat-free mass isn’t measured as often as total bodyweight is. What you could do is to try and estimate what an average body-fat percentage is in those research participants, and adjust the recommended intake from there, but it would still leave you with a lot of unknowns and uncertainty.

Note that there are some exceptions, and in one review, based on six studies, the estimated protein need for resistance-trained athletes in a calorie deficit is 2.3–3.1g/kg of fat-free mass.1

What I would recommend you to do, is to simply wing it a little:

  • If you have trained for a long time, you have a lot of muscle mass, and a pretty low body fat percentage, then adjust your protein intake up.
  • If you are of a pretty normal build, with normal body fat percentage, and your training is pretty average, then just follow the recommendations as they are.
  • And lastly, if you are very overweight, then you can adjust your protein intake down.

One method could be to estimate what would be a normal or “ideal” bodyweight for you, and calculate your protein requirements based on that.

Other Factors Influencing Your Protein Needs

And not only your fat-free mass will affect your individual protein need, but so will your training and calorie intake. Your protein need increase, relative to your total bodyweight, if you are:

  • Very muscular
  • Very lean
  • Training a lot
  • In a calorie deficit

And reversely, your protein needs decrease if you do not have a lot of muscle mass relative to your bodyweight, are not training very much, and are in a calorie surplus.

So with that in mind, you can then take the general recommendations for resistance training individuals, and adjust them slightly up or down. The generally recommended protein intake for strength athletes and bodybuilders is about 1.6–2 grams of protein per kilo, and that is really enough for most of us.2 3 However, if you are cutting and you are already very lean and muscular, you might want to increase that number by maybe 0.5-1 grams per kilo. If you’re not cutting, not super lean or muscular, and you train pretty averagely, then 1.6 g per kilo bodyweight is just fine.

I hope that answers your question, Stefan!

Read more about protein:


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References

  1. Int J Sport Nutr Exerc Metab. 2014 Apr;24(2):127-38. A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes.
  2. J Int Soc Sports Nutr. 2017 Jun 20;14:20. doi: 10.1186/s12970-017-0177-8. eCollection 2017. International Society of Sports Nutrition Position Stand: protein and exercise.
  3. J Nutr. 2017 May;147(5):850-857. Indicator Amino Acid-Derived Estimate of Dietary Protein Requirement for Male Bodybuilders on a Nontraining Day Is Several-Fold Greater than the Current Recommended Dietary Allowance.

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