Scientific evidence suggests that a ketogenic diet may improve physical appearance, performance and health. However, the results on how it actually affects individuals following resistance training are not straightforward. One group of studies states that it may trigger metabolic adaptations that enhance performance in resistance training, while the other warns that it may actually limit it by causing an increased state of fatigue and by hindering the building of the muscle mass. Thus, the authors of this study hypothesized that a high-calorie-ketogenic diet in combination with hypertrophy resistance training would improve body composition in trained men. Specifically, they proposed that it will reduce fat and visceral fat mass plus increase the lean body mass at the same time.
This was an 8-week randomized, parallel, controlled study, which included 24 healthy men with more than 2 years of continuous experience in overload training. They excluded individuals who had consumed androgenic-anabolic steroids during the last 2 years or any type of dietary supplement during the study. The first group consisting of nine participants were instructed to follow a ketogenic diet (<10% of carbohydrates, 20% of proteins and 70% of fat) and a resistance training protocol; the second group consisting of 10 participants followed the training protocol and a defined non-ketogenic diet (55% of carbohydrates, 20% proteins and 25% of fat); while 5 participants presented the control group, and maintained their usual habits. The training intervention was defined as a hypertrophy training protocol, which they performed 4 times per week. The measured outcomes were total and the regional body composition, assessed at the beginning and after 8 weeks of the intervention period.
After 8 weeks, the participants who followed the ketogenic diet and the resistance training protocol significantly reduced their fat mass by 1.1 kg, and the amount of visceral adipose tissue by 96.5 g. The observed reduction in visceral fat may be of importance since it reflects the state of the cardio-metabolic health. None of these parameters changed significantly in the two other groups. Furthermore, the ketogenic diet together with resistance training didn’t change the participants’ total body weight and muscle mass, while the combination of the training and non-ketogenic diet managed to increase them (the total body weight for 0.9 kg and the muscle mass for 1.3 kg). The participants in the control group did not experience any significant changes in their body composition during this 8 week period.
The results of this study imply that the individuals who underwent resistance training together with the ketogenic diet experienced a greater reduction in fat mass and visceral adipose tissue, compared with those who followed the training and the non-ketogenic diet. However, they didn’t manage to increase their lean body mass. Thus the authors concluded that this diet would not be a good strategy for enhancing muscle mass in trained men involved in resistance training.
However, it is noteworthy to point out that individuals with excess fat mass may benefit from this regime, given the fact that it may reduce visceral fat while maintaining the lean body mass. Also, the observed reduction in visceral tissue may be of clinical relevance for the cardio-metabolic health and should be further investigated.
Vargas S, Romance R, Petro JL, Bonilla DA, Galancho I, Espinar S, Kreider RB, Benítez- Porres J. Efficacy of ketogenic diet on body composition during resistance training in trained men: a randomized controlled trial. J Int Soc Sports Nutr. 2018; 15: 31. doi:10.1186/s12970-018-0236-9.