Exercise and fitness have always been really important to me. It’s my natural antidepressant! So, naturally, I wanted to discover how and why my ketogenic diet may affect my fitness abilities….
Your body can only store so much glycogen. Often marathon runners “hit a wall” after burning through their stored glycogen. They often take sport gels and drinks so they can keep going (and not collapse…!). It’s the body’s preferred method of fuel, though there is a finite amount of what the body can store in the muscles and liver. Once it’s gone, it’s gone. However, if you are a fat-adapted athlete you have almost unlimited energy you can tap into. Even a very lean person with 10% body fat has about 54,000 calories of energy stored in the form of body fat- which he can easily access.
If you are an athelte in ketosis, you have literal days of easily accessed energy…. Versus two hours as a sugar burning athlete. fat adapted athlete
What is really interesting is that in a state of ketosis you stay in your fat burning zone longer and burn much more body fat- 230% more body fat than you would on a high-carb diet. You stay in the fat burning zone up to 75% of your VO2 max, as opposed to under 50%. Which means you can work out harder before you get into an aerobic zone.
This really mimics my own experience. I’ll be working out really hard but I’ll stay in a fat-burning zone, at the same level exertion that used to leave me huffing and puffing. I’m burning fat as opposed to glucose.
I’ve also noticed it took time to transition. When I first started I really paced myself, so I wouldn’t place undue stress on my body. A little stress is good, and forces adaptation. A lot of stress is bad and causes too much inflammation. The article above states that it takes athletes at least 5 weeks to fully transition into being efficient, fat-burning athletes. It is a huge metabolic overhaul, after all! I saw that too. I had less stamina and explosive power the first 2-3 weeks. When I would push past 75% VO2 (perceived exertion) my body did not like it. I got dizzy and even nauseous. Though I am now about where I was before in terms of VO2 max. I know this because I like to push myself to the limit with HIIT and Tabata style workouts. I saw an initial hit to my cardio power and endurance but that has leveled out. Workouts are even starting to feel easier!
If you’re an athlete and worried about a decrease in your performance, do some research and stick it out. The decrease is temporary and you’ll come back stronger than ever!