This blog reviews evidence-based recommendations for optimal protein intake for athletes using body composition information.

The Power of Protein

Protein is an important component of every cell in the body from bones to skin to blood to muscle, but protein is also used to make enzymes, hormones and a number of other elements that the body needs. The body is constantly using protein to build and repair tissues that can impact an athlete’s performance. The major factors for determining total protein needs include body composition; training status; intensity and duration of exercise; age; energy intake; type of protein and timing of intake.  This blog will review the importance of using body composition information to determine an athlete’s optimal daily protein intake.
 
How Much Protein Is Enough?
Given the importance of protein in the human body, the question arises: “How much protein do I need to eat?”  In the United States, the recommended dietary intake of protein for healthy individuals is based upon the recommended dietary allowance (RDA) (Medicine, 2005).  The RDA amount varies in different stages of our life and is calculated in grams of protein based on total body weight. This can be problematic since protein recommendations do not account for body composition in athletes, who typically have more muscle than non-athletic individuals of similar body weight.  

For example, let’s compare protein recommendations for an 80-kilogram athlete versus a healthy, non-athlete adult. The RDA for protein (0.8 grams/kilogram body weight) for an 80-kilogram athlete and non-athlete would require 64 grams of protein a day.  On closer examination, the trained athlete may have a larger amount of fat-free muscle mass.  If the 80 kilograms athlete has approximately 8% body fat, the athlete would have approximately 74 kilograms of fat-free mass. In contrast, an 80-kilogram non-athlete may have around 20% total body fat resulting in approximately 64 kilograms of fat-free mass.  In this example, the RDA recommends the same protein intake despite there being a 10-kilogram (22 pounds) difference in fat-free mass. 

A Better Way to Recommend Protein Intake
The above example illustrates the problems with determining protein intake based upon total body weight.  Since muscle is the prime user of protein, a better way to determine protein intake would be to calculate it based upon lean muscle mass (Helms et al., 2014; Geisler et al., 2016).  The most accurate way to determine lean muscle mass is dual X-ray absorptiometry (DXA).  Although there are other ways to determine body composition, many of these, such as underwater weighing, skinfolds, and bioelectrical impedance are all two-component methods of determining body composition.  Two components can only determine fat mass and fat-free mass, which combines lean muscle mass and bone mass. The DXA is a three-component method of measuring body composition and determines skeletal muscle mass as well as fat mass and bone mass. 

For athletes that are trying to maintain body mass while consuming adequate calories, it has been suggested that protein intake should be between 1.63-2.2 grams of protein per kilogram of lean muscle mass (Pardo et al., 2016; Geisler et al., 2016; Johnson Stoklossa et al., 2017).  Using lean body mass to calculate protein needs, an athlete that weighs 80 kilograms with 74 kilograms of muscle would require a protein intake (using 1.63 grams of protein per kilogram lean muscle mass) of approximately 121 grams of protein per day.  However, the 80-kilogram non-athlete with 64 kilograms of muscle mass would need only 104 grams of protein per day. 

It is important to note that the suggested protein intake of 1.63-2.2 grams protein/kilogram lean muscle mass is recommended for athletes that are maintaining their weight and not trying to add lean muscle mass.  For an athlete who is restricting calories in an effort to decrease body fat or to make weight (i.e., wrestlers, boxers, etc.), it is suggested that the rate of protein per kilogram body weight be 2.3-3.1 grams of protein per lean body mass (Helms et al., 2014).  For our 80-kilogram athlete who is trying to wrestle at 74 kilograms, his daily protein intake (using 2.4 grams of protein per lean body mass) would be 170 grams of protein per day.  

Recommendations
The amount of recommended protein per day gets complicated because the amount depends on several factors.  The bottom line is that the optimal protein intake is important in athletes and the use of total body weight to determine total protein intake often underestimates an athlete’s protein needs. The use of lean muscle mass as determined by DXA provides athletes with an improved method to determine total daily protein intake for optimal performance. 
 
References

Geisler C, Pardo CM, Muller MJ. Inadequacy of body weight-based recommendations
for individual protein intake—lessons from body composition analysis. Nutrients 2019, 9, 23; doi:10.3390/nu9010023.

Helms ER, Zinn C, Rowlands DS, Brown SR. A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. International Journal of Sport Nutrition and Exercise Metabolism 2014,24:127-138.

Johnson Stoklossa CA, Sharna AM, Forhan M, Siervo M, Padwal RS, Prado CM. Prevalence of sarcopenic obesity in adults with class II/III obesity using different diagnostic criteria. Journal of Nutrition and Metabolism 2017;http://dx.doi/10.1155/2017/7307618

Medicine IO. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients); The National Academies Press: Washington, DC, USA, 2005; p. 1357.

Prado CM, Cushen SJ, Orsso CE, Ryan AM. Sarcopenia and cachexia in the era of obesity: Clinical and nutritional impact. Proceedings of the Nutrition Society 2016, 75, 188–198.

About the Author: Donald Dengel, Ph.D., is a Professor in the School of Kinesiology at the University of Minnesota and is a co-founder of Dexalytics. He serves as the Director of the Laboratory of Integrative Human Physiology, which provides clinical vascular, metabolic, exercise and body composition testing for researchers across the University of Minnesota.