What is Ketosis?
Under normal physiological conditions, glucose is the primary energy source of the brain. When dietary carbohydrates are restricted and insulin drops, the body becomes stressed and requires an alternative energy source to maintain normal brain cell metabolism. Fatty acids are subsequently mobilized and broken down in the liver to produce ketones. The liver then releases ketone bodies into the bloodstream where they travel to the brain to be used as the new fuel source. Although the ketogenic diet was originally developed as a drug-free way to treat epilepsy, athletes are now voluntarily putting the body into a state of ketosis in order to oxidize fatty acids and use ketones for energy. To achieve ketosis, dietary carbohydrate intake must be restricted to less than 50 grams per day, which is equivalent to one small banana and potato. In a ketogenic diet, around 75% of calories are derived from fats, 20% from protein and the remaining 5% from carbohydrates.
Ketosis and performance
From a performance standpoint, triathlon involves relatively short-duration, high-intensity efforts to boost your anaerobic threshold and as you quickly transition from swim to bike to run, climb hills, accelerate past a competitor and sprint to the finish line. These high-intensity efforts are highly dependent on carbohydrate metabolism and a ketogenic diet may reduce the capacity to utilize carbs, thus compromising your specific energy needs during training and racing. Since you don’t need to be in ketogenic state to improve your fat-burning abilities (thankfully, endurance training will naturally do this for you), focus on a nourishing diet to keep your muscles and liver stocked with glycogen. A well-balanced diet should contain 4-10g/kg/day carbohydrates, 1.5-1.8g/kg/day protein and 1g/kg/day fat.
You probably know that one athlete who has athletically succeeded on a ketogenic diet but there’s far too many athletes who have overhauled the diet to induce ketosis, only to disrupt other body systems which consequently wrecked metabolic and hormonal health and impaired race day performance. As a reminder, your race day performance is influenced by much more than what is occurring inside of you on a cellular level.
Since real life athlete applications have failed to consistently show promising sustainable improvements in endurance performance, more research is needed to establish the effectiveness of a ketogenic diet for triathletes.
To read the article in print, check out the May 2018 issue of Triathlete Magazine (pg. 48).