Should You Calculate Your Protein Needs Via Body Weight or Fat-Free Mass?

Should You Calculate Your Protein Needs Via Body Weight or Fat-Free Mass?

This question comes up a lot when calculating protein requirements and you will commonly hear the fitness cliché of just eat one gram of protein per pound of body weight.

But, is this right?

There is likely quite a bit of wiggle room with this 1 g/lb number and we have broken down how much protein someone might need based on their individualized goals HERE.

Yet, for some people who are living with overweight or obesity the protein amounts from these body weight calculations will likely be too high and for some people who are underweight or very very lean they may even be too low.

The various correction factors (ideal body weight or a BMI correction) are still probably not as good as utilizing Fat-Free Mass (FFM) to calculate protein needs [1].

Additionally, muscle mass is the main determinant of protein needs in the human body so when in doubt is probably best to calculate protein needs from FFM instead of total body weight.

For example, let’s look at how this would play out for 5’ 5” female who is 185 lbs and not resistance training (for reference that is an obese body mass index of around 31). If we used the 1.1 grams per pound calculation that is prototypically recommended for body recomposition her protein would clock in at 203.5 grams per day [2].

This is very likely quite a bit more protein than she needs and if we recalculated this based on the common evidence-based FFM protein factors of 1.0 to 1.5 g/lb of FFM her likely protein needs would drop to between ~100-145 grams per day [3, 4].

That may not seem like too much of a difference, but if she elected to go on a ~1,500 kcal diet with 203.5 grams of protein per day and a reasonable fat factor of 0.3 g/lb she would be left with under 50 grams of carbohydrate. 

This is an amount of carbs that probably isn’t going to be feasible for her in the short or long-term [5, 6]. 

From my experience, I would also argue that this much protein would likely be very hard for her to stick to as well and would ultimately result in a lot of protein shakes and less real food.

Whereas, if we use the ~145 grams per day she would be able to consume a much more feasible amount of carbohydrates at roughly 100 grams per day.

If this person wanted to lose fat and gain muscle at the same time (this is called body recomposition and we have covered it HERE and HERE) I would especially lean towards the higher value of 145 grams per day.

My current guess is that body recomposition would still very likely be possible below that mark [7], but we don’t have any direct studies testing this yet and when someone is in a more severe caloric deficit I would still lean in favor of the higher end of the range at 1.3 to 1.5 g/lb of FFM until we get more data [8].

The idea of establishing protein needs off of FFM gained popularity primarily because of an article published by Dr. Eric Helms in 2014 [3]. The conclusion of this article was, “It appears that the range of 1.0–1.4 g/lb of FFM is the most consistently protective intake against losses of lean tissue [while dieting].”

This study primarily looked and leaner athletes that were dieting and the reason that I have elected to take the higher end range of this up to 1.5 g/lb of FFM in the specific body recomposition scenario is because that is the protein amount that Longland et al. 2016, found was related to significant body recomposition at a 40% energy deficit in untrained individuals [4]. I do think that 1.2 to 1.3 g/lb of FFM in this context will likely do the trick, but I cannot say for certain at this point in time.

If you are wondering about your amount of Fat-Free Mass stop by a store and we can give a solid estimate of your total FFM and one of our RDs can help set you up with a potential individualized protein amount for you.



1. Dekker, I.M., et al., Calculation of protein requirements; a comparison of calculations based on bodyweight and fat free mass. Clin Nutr ESPEN, 2022. 48: p. 378-385.

2. Barakat, C., et al., Body Recomposition: Can Trained Individuals Build Muscle and Lose Fat at the Same Time? Journal of Strength and Conditioning Research, 2020. 42(5): p. 7-21.

3. Helms, E.R., et al., A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. Int J Sport Nutr Exerc Metab, 2014. 24(2): p. 127-38.

4. Longland, T.M., et al., Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr, 2016. 103(3): p. 738-46.

5. Gardner, C.D., et al., Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. JAMA, 2018. 319(7): p. 667-679.

6. Huntriss, R., M. Campbell, and C. Bedwell, The interpretation and effect of a low-carbohydrate diet in the management of type 2 diabetes: a systematic review and meta-analysis of randomised controlled trials. Eur J Clin Nutr, 2017.

7. Ribeiro, A.S., et al., Moderate and Higher Protein Intakes Promote Superior Body Recomposition in Older Women Performing Resistance Training. Med Sci Sports Exerc, 2022.

8. Hector, A.J. and S.M. Phillips, Protein Recommendations for Weight Loss in Elite Athletes: A Focus on Body Composition and Performance. Int J Sport Nutr Exerc Metab, 2018. 28(2): p. 170-177.