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J Sports Med Phys Fitness. 2018 Apr 4. doi: 10.23736/S0022-4707.18.08318-4. [Epub ahead of print]

Low-carbohydrate, ketogenic diet impairs anaerobic exercise performance in exercise-trained women and men: a randomized-sequence crossover trial.

Author information

1
Department of Nutrition and Dietetics, Saint Louis University, St. Louis, MO, USA.
2
Division of Geriatrics and Nutritional Science, Washington University School of Medicine, St. Louis, MO, USA.
3
Doisy College of Health Sciences, Saint Louis University, St. Louis, MO, USA.
4
Department of Nutrition and Dietetics, Saint Louis University, St. Louis, MO, USA - ted.weiss4@health.slu.edu.

Abstract

BACKGROUND:

Low-carbohydrate, ketogenic diets cause mild, sub-clinical systemic acidosis. Anaerobic exercise performance is limited by acidosis. Therefore, we evaluated the hypothesis that a low-carbohydrate, ketogenic diet impairs anaerobic exercise performance, as compared to a high-carbohydrate diet.

METHODS:

Sixteen men and women (BMI, 23±1 kg/m2, age 23±1 yr) participated in a randomized-sequence, counterbalanced crossover study in which they underwent exercise testing after four days of either a low-carbohydrate, ketogenic diet (LC; <50 g/day and <10% of energy from carbohydrates) or a high-carbohydrate diet (HC; 6-10 g/kg/day carbohydrate). Dietary compliance was assessed with nutrient analysis of diet records, and with measures of urine pH and ketones. Anaerobic exercise performance was evaluated with the Wingate anaerobic cycling test and the yo-yo intermittent recovery test.

RESULTS:

The diets were matched for total energy (LC: 2333±158 kcal/d; HC: 2280±160 kcal/d; p=0.65) but differed in carbohydrate content (9±1 vs. 63±2% of energy intake; p<0.001). LC resulted in lower urine pH (5.9±0.1 vs. 6.3±0.2, p=0.004) and the appearance of urine ketones in every participant. LC resulted in 7% lower peak power (801±58 vs. 857±61 watts, p=0.008) and 6% lower mean power (564±50 vs. 598±51 watts, p=0.01) during the Wingate test. Total distance ran in the yo-yo intermittent recovery test was 15% less after LC diet (887±139 vs. 1045±145 meters, p=0.02).

CONCLUSIONS:

Short-term low-carbohydrate, ketogenic diets reduce exercise performance in activities that are heavily dependent on anaerobic energy systems. These findings have clear performance implications for athletes, especially for high-intensity, short duration activities and sports.

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