Ketogenic diets are characterized by a reduction in carbohydrates (usually to less than 50 g/day) and a relative increase in the proportions of protein and fat (Paoli et al., 2013). The excellent review of Paoli et al. (2015) explains the differences between the physiological and pathological ketosis indicating the potential benefits of ketogenic diets for weight loss. As highlighted by the authors, the physiological ketosis, it is not a pathological situation such as observed in diabetic ketosis. For athletic weight loss, if necessary, a ketogenic diet may be a viable route but at least 2 weeks of adaptation are necessary to avoid negative effects on performance.
The recently published manuscript of (Wilson et al. (2017), investigated the impact of isocaloric (~2600 kcal/day) and isonitrogenous (similar amount of proteins) ketogenic diet (20%, 5% and 75% calories from protein, carbohydrate, and fat respectively) versus a traditional western diet (20%, 55% and 25% calories from protein, carbohydrate, and fat respectively) on body composition, performance, blood lipids and hormonal profile in resistance trained males. Twenty-five males were randomly allocated into a ketogenic (n = 12) or a traditional western (n = 13) diet group. After 2 weeks of familiarization, the participants followed a periodised 8-weeks resistance training programme aimed to increase muscle mass and strength. At the end of the programme (week 10) the ketogenic group increased the amount of carbohydrate (reintroduction strategy) for 1 week. Participants were assessed at week 0 (before the familiarization) at week 10 (after the 8-week of resistance training programme) and at week 11 (after the carbohydrate reintroduction). Lean body mass increased in both ketogenic (2.4%) and traditional (4.4%) groups at week 10, however only the ketogenic group increased lean mass from week 10 to 11 (4.8%). Fat mass decreased in both groups (-2.2 kg ± 1.2 kg and -1.5 ± 1.6 kg for ketogenic and traditional diet respectively). Strength (1RM) and power (determined by Wingate test) increased in both groups. Testosterone concentration increased in the ketogenic (118 ng/dl) as compared to the traditional (-36ng/dl) diet while insulin and lipid profile did not change. Furthermore, the raise from ~0.4 g/kg toward 1 and 3 g of carbohydrate at week 11 resulted in an increase of serum triglycerides in the ketogenic group. Authors concluded that ketogenic diets configure a good option to support favourable changes in body composition, performance and hormonal profile in resistance-trained males. Although, the results of the present investigation advocate for the use of ketogenic diets in resistance-training, some details need to be considered:
1) The diets caloric content was estimated based on the Mifflin St. Jeor equation that predicts resting metabolic rate and consequently it is not clear how the energy expenditure from activities, including the planning exercises, the spontaneous physical activities, as well as the non-exercises activities thermogenesis was calculated (Thomas et al., 2016)
2) The participants performed no other physical activities during the study. Consequently, results should be considered cautiously when designing diets for other athletes such as footballers, rugbies, boxers or judoists in which resistance training are integrated with other highly metabolic demanding activities where the amount and type of carbohydrates would affect both recovery and training outcomes. Additionally, for a better applicability and comparison with others studies, it would be appreciated if the nutrients were reported in grams per kg body mass (Thomas et al.,)
PAOLI, A., BIANCO, A. & GRIMALDI, K. A. 2015. The Ketogenic Diet and Sport: A Possible Marriage? Exerc Sport Sci Rev, 43, 153-62.
PAOLI, A., RUBINI, A., VOLEK, J. S. & GRIMALDI, K. A. 2013. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. Eur J Clin Nutr, 67, 789-96.
THOMAS, D. T., ERDMAN, K. A. & BURKE, L. M. 2016. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet, 116, 501-28.
WILSON, J. M., LOWERY, R. P., ROBERTS, M. D., SHARP, M. H., JOY, J. M., SHIELDS, K. A., PARTL, J., VOLEK, J. S. & D’AGOSTINO, D. 2017. The Effects of Ketogenic Dieting on Body Composition, Strength, Power, and Hormonal Profiles in Resistance Training Males. J Strength Cond Res.