Low carb 'ketogenic' diets can impair anaerobic exercise performance when compared to a high-carbohydrate diet, according to a new study.
The study, titled Low-carbohydrate, ketogenic diet impairs anaerobic exercise performance in exercise-trained women and men: a randomized-sequence crossover trial, was published in The Journal of Sports Medicine and Physical Fitness.
Researchers tracked the performance of 16 participants - men and women - who followed either a low carb diet (less than 50g of carbs a day and less than 10 percent of energy intake) or a high carb diet (between six and 10g of carbohydrate per kg of body weight per day).
Dietary compliance was assessed with nutrient analysis of diet records, and with measures of urine pH and ketones - which are easy to test for in urine when the body has reached a state of ketosis after carbohydrate restriction.
Researchers tracked and compared the performances of the participants. They found those following the ketogenic diet lowered their average and peak performance power levels and ran shorter distances as well, compared with those who ate a high-carbohydrate diet.
The results suggest low-carbohydrate diets impair intense, short-term physical activities.
The report's authors concluded: "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."