The Effects Of A Six-week Ketogenic Diet On The Performance Of Short-duration, High-intensity Exercise

Abstract

There is much controversy surrounding the use of very high fat, low carbohydrate ketogenic diets and athletic performance. Specifically, it has been hypothesized that anaerobic activity, which is primarily fueled by ATP that is formed through the metabolism of carbohydrate sources, may be hindered when utilizing a ketogenic dietary approach. PURPOSE: The current study was designed to investigate how switching from a habitual diet to a ketogenic diet for 6 weeks would affect the performance of short-duration, high-intensity exercise. METHODS: Eight men and seven women (N = 15; 30.2 yr ± 4.11) were randomly assigned to either the ketogenic diet (KETO; n = 8) or the control group (CON; n = 7). All subjects were trained in CrossFit for at least 3 months prior to the study. Several measures of anaerobic performance were assessed at baseline and following 6 weeks utilizing the following series of standardized exercise tests: timed 500m row, Wingate Anaerobic Test, and 3-repetition maximum (3RM) deadlift. Aerobic capacity was also assessed by measuring VO2peak. Subjects continued their regular CrossFit training during the 6 week period and dietary intake was recorded. RESULTS: A significant increase (p < .05) in mean power output (MPO; W/kg) from baseline (M = 8.24 ± 1.15) to 6 weeks (M = 8.70 ± .82) was found the CON group. No significant interactions (p > .05) were found between diet and test time for any of the other measured exercise variables. No significant differences (p > .05) were found in the KETO group from baseline to 6 weeks in any of the measured exercise variables. No significant differences in body weight (lbs) were found from baseline to 6 weeks in either group (KETO; 183.8 ± 31.71 vs. 181.03 ± 30.28, CON; 166.38 ± 35.77 vs. 166.88 ±37.28). Attrition rate was 33% in the KETO group and 30% in the CON group. CONCLUSION: A 6-week ketogenic diet did not affect the performance of short-duration high-intensity exercise. Our data does not support the hypothesis that ketogenic diets induce detriments in the performance of activity that is anaerobic in nature. The current study took place over a 6 week period, allowing for keto-adaptation to occur; results may be different if a shorter time period were utilized.