Ketogenic or Low Carb High Fat (LCHF): is it appropriate for your sport?

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The concept of LCHF has been explored in waves over the past 50 years and has recently jumped back into life via expert opinion, social media and anecdotal evidence. The focus of the current LCHF movement involves limiting carbs to <30g or <50g per day and providing 75-80% energy from fat. Consuming these levels of fat usually requires a diet based on a significant amount of cheese, cream, nuts, ‘grass-fed’ meat fat, nuts and oils. With the aim of this diet being to increase ketone levels to achieve “ketosis” (not to be confused with ketoacidosis). Hence the ‘keto diet’ or ‘ketogenic diet’.

There is no question that by following a LCHF diet you will be able, in as short as 5 days, to burn  more energy from fat in your muscles. Sounds good so far. Within three weeks you can achieve ketosis and reduce reliance on carbohydrate for fuel. However, the ability to perform high intensity exercise is compromised by not having the stores of carbohydrate or the ability to readily access it. Furthermore, the body is more efficient at burning glucose than other energy sources.  Based on recent research, your perceived effort will increase for a given high intensity workload on a LCHF diet, meaning that it will feel like you are working harder to perform at the same level.

You may be thinking that most of your exercise is at lower intensities, however anytime we call upon a higher intensity: be it running up a hill, accelerating out of a turn or performing multiple reps, we will call upon higher energy states. If you were performing ultra-distance exercise at sub-maximal intensities or where access to carbs or any food is an issue, then a LCHF approach may be of benefit to you. Though the long term health effects by following such a diet are unknown.

For most sports, there is no question that carbohydrate intake, individually prescribed will facilitate faster times, better training responses and less effort at higher intensities. While it is easy to get caught up with the hype of trying something new, sometimes we need to step back and look at the evidence. For more information or to discuss eating around training, consult with a Sports Dietitian.

Peter Herzig (AccSD, APD)

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