The ketogenic diet has taken the world this storm this year becoming one of the most googled diets. As always happens when something becomes extremely popular, benefits can become inflated. If you’re considering trying a ketogenic diet, it’s important to sift through the hype and determine what the truth is. And if you’re an athlete, you don’t want to put your performance on the line due to misinformation. Therefore, this article will give you a quick overview of the ketogenic diet and look at what happens when strength trainees go on a ketogenic diet.
Originally designed in the 1920s as a diet to treat epilepsy by decreasing the seizure threshold in brain neurons, the ketogenic diet is a high-fat, very low-carb diet that forces the body to shift from burning glucose (from carbs) to burning ketones, which are byproducts of fat that are produced by the liver. Being vastly different from the high-carb, low-fat diet that was popularized in the late 20th century, the ketogenic diet has been shown to have several metabolic benefits that pay off in terms of better health and body composition.
Studies show that ketogenic diets lower insulin levels, improve glucose tolerance, and are a viable treatment for type 2 diabetes. They can treat brain disorders and may improve cognition. They also lower circulating triglycerides and blood pressure and may have beneficial effects on cardiovascular health and function.
Where the ketogenic diet really shines is in terms of reducing body fat: Diets high in fat and low in carbs blunt appetite, leading people to automatically eat fewer calories. This means that calorie counting and restriction are often unnecessary when trying to lose body fat on a ketogenic diet. Of course, ketogenic diets ratchet up fat burning, allowing your body to access its own fat stores for energy as glucose levels drop. When combined with strength training there is also evidence that ketogenic diets preserve muscle mass so that improvements in body composition are more sustainable for the long-term.
What about building muscle? Is it possible to put on mass on a ketogenic diet? How does a ketogenic diet impact strength and power performance?
After all, we know that for high-intensity exercise, glucose is the preferred fuel source. Reducing carb intake can lead to decrements in high-intensity performance, such as repeated sprints, sports performance, or high-volume strength training with short rest periods.
A new Spanish study provides some insight: Researchers recruited young resistance trained men and put them on either a ketogenic or a traditional higher carb diet for 8 weeks. The diets were designed to provide more than enough calories to sustain energy needs, so daily energy intake was set at 39 calories per kg of bodyweight. The ketogenic diet provided 42 grams of carbs daily, 2 g/kg of protein, and the remaining calories (about 3.2 g/kg) from fat. The traditional diet was 55 percent carbs, 20 percent protein, and 25 percent fat. Training was 4 days per week with an upper/lower body split and a protocol of 6-8 RM, 3 sets, with 3 minutes rest, trained to failure.
Results were as follows:
The ketogenic diet group lost 1.1 kg of body fat and had a significant decrease in visceral belly fat. As a group, they maintained muscle mass, although there was significant variation in lean mass changes, with a standard deviation of 6.9 kg compared to a variation of 4.2 kg in the traditional group.
The traditional diet group had a small decrease in body fat of 0.4 kg, a small decrease in visceral fat, and an increase of 1.2 kg in muscle mass.
Researchers concluded that the ketogenic diet is a useful dietary approach for decreasing both body fat and belly fat, without the unpleasant effects of calorie restriction or losing muscle. It can be used in already lean subjects who are involved in intense training to optimize body composition. Subjects whose primary goal is to increase muscle mass will likely get better effects from higher carb intake, such as that used by the traditional diet group.
One drawback of this study is that it didn’t report athletic performance or strength development, so we don’t know how the ketogenic diet impacted training performance. Strength training relies on both the phosphagen pathway that burns phosphocreatine and the glycolytic energy system that burns carbs, making higher carb diets useful in some situations when performance is the priority.
Ketogenic diet studies on strength athletes are limited but we do have the well-known trial that used Italian national team gymnasts that showed that a month of ketogenic eating resulted in the maintenance of strength and power performance along with the loss of 2 kg of body fat so that the gymnasts ended the trial with a body fat of 5 percent.
The takeaway is that a ketogenic diet is a great tool for leaning up without “dieting” or the misery of calorie restriction. Fat loss shouldn’t be an all the time thing, so you can employ a low-carb, high-fat diet for a few training cycles, lose those love handles, and get back to more performance-focused eating. Higher carb diets will generally be your go-to choice when putting on mass is the goal.
Paoli, A., et al. Ketogenic diet does not affect strength performance in elite artistic gymnasts. Journal of the International Society of Sports Nutrition. 2012. 9(34).
Vargas, S., et al. Efficacy of ketogenic diet on body composition during resistance training in trained men: a randomized controlled trial. Journal of the International Society of Sports Nutrition. 2018. 15(31).