Ketogenic diet for lifters
Popularised in the 90s as the Atkins diet, the ketogenic diet, or keto, is controversial. Depending on who you ask you'll hear that it's a dangerous fad, the holy grail of simultaneous fat loss and muscle retention, the key to mental superpowers, and everything in between.
The truth is... complicated. Many lifters have successfully used keto diet plans to cut fat and retain muscle, and keto dieters often report greater focus and mental clarity, all while eating things that average dieter would kill for. But common mistakes, like the idea that you can pig out on bacon all day and look like Arnold, often derail people's progress, and some claim keto is no more effective than other calorie controlled diets. Let's take a closer look.
The average body needs about 2000 calories a day to maintain homeostasis – a fancy word for equilibrium in biological systems. Most of the time, at least in agricultural societies, people get the majority of these calories from carbohydrates, which the body converts into glucose to fuel the brain, muscles, and everything else.
But something interesting happens when you stop consuming carbs. After the glucose stored in your liver is used up – which takes about a day – it begins a process of fatty acid oxidisation in order to generate energy, turning fat into a molecule called acetyl-CoA. After a few days of this the liver has accumulated enough acetyl-CoA to further convert it into ketone bodies, which are then used as fuel for the body, in place of glucose.
This state of continual ketone production and use is what we call ketosis. The way dieters enter ketosis is simple: eat a high fat, moderate protein, very low carb diet. A ratio of 10% of calories from carbs, 20% from protein, and 70% from fat is a good start.
Should lifters do keto?
Sure, it's possible to lose fat without ever entering ketosis, and my personal preference is for a moderate carbohydrate, high protein intermittent fasting protocol (which might be explored in another article) but there's no denying it: keto works. You still have to manage your calorie intake, like on any other diet, but the argument goes that keto diets are more satiating, and provoke less of an insulin response, making it much easier to refuse that second helping.
But more importantly for lifters, keto advocates claim that by making the body less dependent on glucose as a fuel, you can avoid gluconeogenesis – the process by which the body converts protein, including muscle mass, into glucose – meaning weight loss comes almost exclusively from body fat, rather than muscle.
This is a controversial claim, and there's evidence for both sides of the debate. But let's focus on one recent study which seems to bear the keto dieters' argument out.
Keto’s metabolic effects
In 2016 researchers at the University of Connecticut split 20 ultra-marathon runners and ironman triathletes into two groups of 10. One group was put on a traditional high carb calorie restricted diet with a macronutrient ratio of around 60% of calories from carbs, 15% from fat, and 25% from protein. The second group was put on a ketogenic diet of roughly 10% carbs, 20% protein, and 70% fat (Volek, et al. 2016).
After an average of 20 months on these diets the athletes underwent a battery of tests, including a VO2 max test and a 3 hour run, during which fat oxidation was measured with indirect calorimetry, as well as blood tests and muscle biopsies taken at regular intervals.
The results were astounding. Mean fat oxidation in the ketogenic group was 2.3 times that of the high carb dieters, and peaked at a higher percentage of their VO2 max -- 70.3% vs 54.9% -- essentially meaning they had greater capacity to burn fat by working harder, and muscle glycogen depletion was almost identical between groups, despite the keto dieters eating almost no carbs for 20 months prior to the tests.
So not only did the keto dieters have over double the capacity to burn fat, but did so while maintaining normal glycogen concentrations, meaning for every pound of bodyweight lost keto dieters are likely to lose double the fat, and correspondingly less muscle, than high carb dieters.
Should you do it?
The answer is maybe. This study seems promising, and plenty of others back it up, but these were endurance athletes, and some research shows no real difference in fat loss and muscle retention over time between keto and other calorie restricted diets. On top of that many coaches warn strength athletes who rely on explosive power off keto at competition time, fearing they won’t have enough muscle glycogen to perform optimally. Though the same could be said for any calorie restricted diet.
As is often the case with sports nutrition research the take away seems to be: try it, if it works for you -- great. If not -- try something else. Anyway, for recreational lifters there’s not much to lose, and the chance to lean out while eating steak and eggs has got to be worth a shot, right?
Volek, J., Freidenreich, D., Saenz, C., Kunces, L., Creighton, B., Bartley, J., Davitt, P., Munoz, C., Anderson, J., Maresh, C., Lee, E., Schuenke, M., Aerni, G., Kraemer, W. and Phinney, S. (2016). Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism, 65(3), pp.100-110.