I’m a runner so I understand what it’s like to train/exercise while you’re reducing your carb intake. There are lots of people out there who train and run marathons even in a heavily ketogenic state.
As I’ve said all along we eat way too many carbohydrates and we have this weird reliance on it thinking that it’s going to fuel us and sustain us before exercise but the majority of us actually have energy stores in our bodies to fuel us for a very long time. Of course see how you feel and note how your endurance levels are but have confidence in your amazing body and know that you can do it without having a big carb laden plate of creamy risotto beforehand! Carb loading is a very popular preparation tool before a marathon or long training session but there are many many people out there who prefer quite the opposite. For your quick sprint in the gym or your 45 minute HIIT class you do not need to carb load at all. Often when people are eating fewer carbohydrates they feel lighter, faster and much more energised.
When following a low carb high fat lifestyle we are massively restricting our carbohydrate intake and therefore limiting the ability of our muscle cells to access sugar- one of the fastest fuel sources that the body relies on. When our muscles don’t have enough sugar, their ability to function at high intensities (for any activity that lasts longer than 10 seconds) is impaired. This happens because after around 10 seconds of near maximal to all-out effort the muscles start to rely on glucose for energy by using a metabolic pathway called glycolysis instead of the phosaphen system (which depends on creatine phosphate and ATP, not glucose). So any muscular activity that requires near maximal to all-out effort for 10 seconds to about 120 seconds can only be fueled by glucose. Fat and ketones cannot stand in for glucose in the glycolytic pathway at all. Only after around 2 minutes of exercise will your body start to shift to metabolic pathways that can burn ketones and fat.
So on this plan when we restrict carbs, we deprive our muscle cells of the sugar that it needs to fuel activities that require a high-intensity effort for 10 seconds to 2 minutes.
Start with a standard ketogenic low carb high fat diet (fewer than 35 grams of carbs per day), and assess how that affects your exercise performance after 1 to 2 weeks. See how you feel during your exercise periods. If you notice no effect or an increase in endurance, then keep your carb limit as it is. If you are struggling, then consider increasing your carb limit or supplementing with MCT oil in your coffee or smoothie prior to your work out. It’s really important to note how YOU feel.
Some great forms of exercise while on a low carb high fat plan are:
Benefits can include fat burning, endurance boosting, can support muscle growth and can speed muscle recovery.