Non keto-athletes and serious exercisers often talk about how on a ketogenic diet we lack lack the pathways to gain muscle and improve performance. THIS IS NOT TRUE! And here is the scientific reasons why!
Jeff Volek and Stephen Phinney, are leading researchers in the field of keto adapted athletic performance, they have debunked this myth completely, and documented some of their findings very well in their co authored book "The Art and Science of Low Carbohydrate Performance".
The most talked about "draw back" of a ketogenic diet for athletes is that lean muscle mass production slows, and muscle protein synthesis is negatively effected. This in fact, couldn't be farther from the truth. We have all heard of the positive body composition changes from the burning of fat for fuel in a ketogenic diet, but it turns out that the reduction in body fat percentage is amplified due to the ability to maintain and increase lean muscle mass. Volek and Phinney state in their book that, "Evidence clearly indicates that a well formulated ketogenic diet spares the body's proteins from oxidation". This is possible due to the fact that the structure of ketones resemble that of the amino acids that are metabolized in a standard western diet, therefor are burned as a substitute. This allows blood levels of Branched Chain Amino Acids to stay elevated in ketogenic metabolism. The misconception of a detriment to muscle protein synthesis, or MPS, is rooted in the fact that insulin is regarded as a key factor in promoting MPS, and as we know, without the influx of glucose in the blood stream, an insulin response is not triggered. It turns out the Branched Chain Amino Acid, Lucine, easily fills the role of the missing insulin and is able to promote MPS in its own right. This, combined with the protein sparing effects of ketosis that up regulates lucine levels, muscle protein synthesis is promoted at levels just as high, if not higher than diets that include high amounts of carbohydrates to stimulate insulin production. In addition this lack of insulin response allows anabolic hormones such as testosterone and human growth hormone, which play a large role in exercise recovery and muscle regeneration, to be at an all time high.
Perhaps the most significant improvement, when converting metabolism to a fatty acid fuel source, is the practically endless supply of fuel, in comparison to the finite amount of carbohydrates we are able to store as muscle and liver glycogen. When glucose is not directly metabolized to create ATP, it is converted and stored as glycogen in the liver and skeletal muscle throughout the body. On average these glycogen stores can hold around 400-500 grams of glycogen, to later be burned as glucose, accounting for 1600-2000kcal of energy. This is when we begin to see that this fuel reservoir doesn't begin to compare to the energy stored in fat, even in extremely lean individuals. Each gram of fat contains 9kcal of energy which is more than double that of the energy of carbohydrates, to go further, the storage capacity of fat is endless, even in a lean 10% body fat athlete, the energy available in the fat fuel tank is about 20x that of the energy in the carb fuel tank, somewhere around 40,000kcal. This expanded fuel tank rids athletes of the need to carb load and continuously provide nutritional energy throughout high endurance exercise, such as marathon running and competing in triathlons. Which is why in the past decade athletes on ketogenic diets have emerged as some of the best performers in these ultra endurance competitions.
These next two ketogenic improvements to overall athletic performance go hand in hand. They are the improvements in ventilatory drive and the production and regulation of lactate during exercise. One of the largest drivers of respiratory rate during exercise is the acidity, or pH of the blood. The two pathways that increase acidity, and decrease pH, are high amounts of carbon dioxide and high amounts of lactate in the blood stream. During exercise, as exertion increases these chemicals are produced at a higher rate than they can be dealt with, causing levels in the blood to raise, and resulting in increased respiratory rate or hyperventilation. In the metabolization of fat, less C02 is produce per calorie burned, resulting in less build up in the blood. In addition with much less reliance on the burning of glucose through glycolysis in a ketogenic diet, significantly less lactate is present in the blood stream, making it easier to regulate respiration, in other words, its easier to breath.