You are what you eat, but have you ever put effort to take a deeper look into your nutrition? In CrossFit, nutrition has been a hot topic all the way through its establishment from the 1990’s.
CrossFit has its own nutrition guidelines guiding athletes to eat relatively low amounts of carbohydrates: 40 E% (share of total energy, E%) of carbohydrates, 30 E% of proteins and 30 E% of fats, and this is believed to represent healthy and macronutrient-balanced nutrition. CrossFit’s founder Glassman (2002) states that diets including more carbs and less protein and fats lead to elevated risk of e.g. cancer and diabetes or result in weak physical performance. Still, these dietary recommendations used within the CrossFit community are mainly based on anecdotal rather than on research-based evidence (Escobar et al. 2016).
Research-based evidence shows that in high-intensity and high-volume sports such as CrossFit, athletes benefit from a diet that is high in carbs (50-70 E% of carbs, 20-30E% of protein and 30-45 E% of fats) (McArdle et al. 2010). These recommendations are known as strength and power athlete dietary recommendations.
This interesting confrontation between CrossFit’s own dietary recommendations and research-based dietary recommendations made me want to take a deeper look into what do CrossFit athletes actually eat? My master’s thesis in Exercise Medicine focused on the dietary habits of competitive CrossFit athletes in Finland.
Comment from the researchers
Nutrition plays an important role for the optimum health, optimum performance and optimum results in training (Aerenhouts et al. 2010). Nutrition has three important roles in strength-power sports, as it acts
- as a fuel for the body in the strength-training,
- as a recovery substance from the training, and
- as a promoter for the adaptations of the training, e.g. skeletal muscle hypertrophy (Slater and Phillips 2011).
According to researchers, CrossFit athletes may not be able to reach the optimal performance levels with moderately-low level carbohydrate diets. For short training periods (e.g. for three days), moderate levels of carbohydrates may be a suitable solution for performance demands. However, over long training periods such as for weeks and months, too low carbohydrate intake levels will reduce glycogen stores and weaken performance. (Escobar et al. 2016)
Low-carbohydrate diet damages exercise capacity and the ability to perform high-intensity aerobic exercises, as the levels of muscle and liver glycogen are reduced. On the other hand, if you eat too much carbohydrates, the body stores it as fat. (McArdle et al. 2010) CrossFit training’s metabolic profile is “glycogenolytically-demanding”, and therefore diet that includes moderately-low levels of carbohydrates may not provide tools for improving performance. CrossFit includes high cardiorespiratory activities, which again increase the need for glycogen utilisation and availability, and therefore high and continuous glycogenolytic energy production is essential. (Escobar et al. 2016) The American College of Sports Medicine (2016) concludes that high-carbohydrate intake makes it possible for the athlete to maintain exercise performance in prolonged or continuous high-intensity exercise.
Research about CrossFit athletes’ nutrition
Total of 29 competitive-level CrossFit athletes participated in this research during Summer-Autumn 2017. Athletes filled a 3-day food and training diary and provided background information of themselves. All athletes had competed in the largest Finnish CrossFit competitions (Karjalan Kovin, Unbroken, Winter War) in 2015-2017.
Athletes’ estimated carbohydrate intake of 4.2 g/kg (41 E%) was below strength and power athlete recommendations, but within CrossFit recommendations. Mean estimated protein intake of 2.5 g/kg (26 E%) met strength and power athlete and CrossFit recommendations. Mean estimated fat intake of 1.5 g/kg (34 E%) was also within both dietary recommendations.
The athletes’ diets got pretty close to the strength and power athlete recommendations, as only carbohydrate intake was not in line with the recommendations. Carbohydrate intake was the closest to CrossFit dietary recommendations.
What to take home from this?
CrossFit’s nature as high-intensity cardiorespiratory sports and the demand for the athlete to maintain maximal power are vital features for the competitive athletes. Hence, it can be questioned if the high-performing athletes in CrossFit benefit from nutrition that does not reach the research-based dietary recommendations, i.e. strength and power athlete recommendations. Another interesting topic for future research would also be, whether or not low-carb diet affects athlete performance negatively.
As CrossFit is a relatively young sport, there are diversities in best practices for nutrition. To date, CrossFit nutrition hasn’t been a popular topic to research, and researchers do not agree about the ideal diet for CrossFit athletes. Therefore, athletes may become uncertain about what is the best diet for them.
Before there is more research about the subject, athletes should apply previous research-based practices with small adjustments, i.e. implement the strength and power athlete dietary recommendations to CrossFit athlete’s diet.
References
Aerenhouts D, Deriemaeker P, Hebbenlinck M, Clarys P. 2010. Energy and macronutrient intake in adolescent sprint athletes: A follow-up study. Journal of Sports Sciences 2011;29(1);73–82.
American College of Sports Medicine and Academy of Nutrition and Dietics, Dietitians of Canada. Thomas T., Erdman K., Burke L. 2016. Nutrition and athletic performance. Joint position statement, special communications. Official Journal of the American College of Sports Medicine 2016;48(3);543–568.
Escobar K, Morales J, Vandusseldorp T. 2016. The effect of a moderately low and high carbohydrate intake on CrossFit performance. International Journal of Exercise Science 2016;9(4):460–470.
Glassman G. 2002. What is fitness? The CrossFit Journal, October 2002. http://crossfit.com
Ihatsu J. Dietary habits of competitive CrossFit athletes in Finland. Master’s thesis. Exercise Medicine, University of Eastern Finland 2018. Available here: http://epublications.uef.fi/pub/urn_nbn_fi_uef-20180538/
McArdle W, Katch F, Katch V. 2010. Exercise physiology. Nutrition, energy and human performance. Seventh edition. Lippincott Williams & Wilkins, a Wolters Kluwer Business.
Slater G, Phillips S. 2011. Nutrition guidelines for strength sports: Sprinting, weightlifting, throwing events, and bodybuilding. Journal of Sports Sciences 2011;29(1);67–77.
