The Fat-adapted Athlete

Traditionally athletes have valued carbohydrates as the most efficient fuel source, with many partaking in ‘carb loading’ prior to race day in order to optimise performance and endurance. Although it is true that our body prioritises glucose if it is available, the body has a very clever way of producing energy that can sustain physical performance in the face of a glucose shortage. This is known as fat adaptation and can be achieved by eating a diet lower in carbohydrates and higher in good fats which in turn allows the body to efficiently burn fat as a fuel source.

A potential issue with a high carbohydrate intake long term is an associated increased risk of insulin resistance and cardiovascular disease, conditions we normally associate with the overweight and sedentary. This disorder can even occur in athletes training 20+ hours per week and is referred to as the ‘athlete’s paradox’. ‘Carbohydrate intolerance describes the decreased ability to process carbohydrates effectively. Insulin resistance is, in essence, carbohydrate intolerance due to the decreased responsiveness to insulin in the peripheral tissues which leads to de novo lipogenesis (fat synthesis by the liver) and consequent increased risk of several chronic diseases.’

‘Sufficient restriction of dietary carbohydrates puts the body into a state of nutritional ketosis in which energy metabolism is diverted to utilizing fatty acids directly for creating ATP or ‘ketones’ (e.g. beta-hydroxybutyrate). Over a period of time, the body adapts to efficiently using ketones as a predominant fuel source both peripherally and within the central nervous system in a state known as keto-adaptation. For example, the brain can derive roughly two thirds of its energy from ketones.’ (Metagenics, 2015; Volek, J.)

In the past we have relied on glucose replacement during training to avoid ‘hitting the wall’. However, recent science has associated fat-adapted training with improved athletic performance. One of the many benefits of having a reduced amount of carbohydrate in your diet is the improved ability to burn fats as fuel, meaning you are more metabolically flexible.

Mike Morton, Master Sergeant, US Army Special Operations Command, American 24-hr Distance Running Record (172 miles): ‘I switched to a low-carbohydrate/high-fat lifestyle in 2012 and was able to win back to back 100-mile races one week apart including setting a course record. The diet has transformed my health and performance.’ The level of carbohydrate required varies per individual depending on metabolic health and training goals. If you would like to know more about fat-adapted training and if it is suitable for you, make an appointment to discuss your needs.


Written by Naturopath Phillip Chua

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