Abstract

A low-carbohydrate ketogenic diet (LCKD) is a popular approach to weight and fat loss. CrossFit is a high-intensity power training (HIPT) type exercise for all levels of age and fitness that has gained recognition as one of the fasting growing sports in America. No previous research has been found which examines body composition changes or performance in individuals consuming a LCKD and participating in CrossFit training. PURPOSE: The purpose of this research was to examine the effects of a 6-week LCKD and CrossFit program on body composition and performance. METHODS: Twenty-seven non-elite CrossFit subjects (mean ± SD age = 34.58 ± 9.26 years) were randomly assigned to a LCKD (males, n = 3; females, n = 9) or control (CON) (males, n = 2; females, n = 13) group. LCKD was instructed to consume an ad libitum diet and restrict carbohydrate intake to less than 50 grams per day (RESULTS: Compared to the CON group, the LCKD group significantly decreased weight (0.18 ± 1.30, -3.45 ± 2.18 kg), BMI (0.07 ± 0.43, -1.13 ± 0.70 kg/m2), percent body fat (%BF) (0.01 ± 1.21, -2.60 ± 2.14%), and fat mass (FM) (0.06 ± 1.12, -2.83 ± 1.77kg), respectively. There was no significant difference in lean body mass (LBM) change between or within groups. We found no significant difference in total performance time change between the CON group and the LCKD group; however, both groups significantly decreased total performance time (CON: -41.20 ± 43.17 sec.; LCKD: -55.08 ± 44.29 sec.). Additionally, there were no significant differences in vertical jump and standing long jump change between or within groups. For both groups, the overall change in vertical jump was significant (2.31 ± 4.55 cm) but the change in standing long jump was not. Carbohydrate intake was significantly lower (11.4 ± 5.6%, 40.06 ± 6.81%) and fat intake was significantly higher (62.88 ± 4.19%, 38.38 ± 4.18%) in LCKD at weeks 2, 4, and 6 compared to CON, respectively. There was no statistical difference in total kilocalories or protein intake between or within groups throughout the study. CONCLUSION: A LCKD combined with 6 weeks of CrossFit training can lead to significant decreases in %BF, FM, weight, and BMI while maintaining LBM. Additionally, significant improvements in total performance time and power can be achieved. PRACTICAL APPLICATION: With the overwhelming increase in obesity and metabolic disease throughout the United States many Americans are searching for the most effective diet and exercise program which promotes fat loss and increases overall quality of life. This study provides valuable insight into the use of a LCKD combined with CrossFit training for 6 weeks to improve body composition and performance outcomes.