Performance

A low-carbohydrate, fat-adapted athlete can run marathons using just the body’s own fat stores for fuel. Research suggests that a fat-adapted athlete oxidises more fat per minute than an athlete who eats a carbohydrate diet. On average, a fat-adapted athlete burns 1.5 grams of fat per minute, compared to a maximum of just 1 gram per minute (although often much less ) by an athlete eating a high-carbohydrate diet (2)(3).     

Carbohydrates are stored as glycogen in the liver and the muscles until they are needed for energy. However, even a lean person with a low body fat percentage still stores 15 to 30 times more energy in their fat (adipose tissue) then they do as carbohydrate (3)(4). The huge storage capacity of adipose tissue can provide ongoing energy – perfect even for endurance athletes (5)(6).

Once adapted to a low-carbohydrate diet, the body can unlock, access and oxidise adipose tissue, decreasing reliance on circulating glucose and muscle glycogen – reducing fatigue, and maintaining energy over long periods of time (7). Low-carbohydrate adapted athletes dramatically increase fat oxidation, yet maintain normal skeletal muscle glycogen concentrations (8).  Studies in athletes have shown no differences in rates of glycogen synthesis in the muscle during post-exercise recovery, despite very little carbohydrate in the diet.  Fat is burned, and lean muscle mass is preserved.

Instead of burning glucose, one of the fuels a fat-adapted body will burn is ketones – which can be used not only by skeletal muscles during exercise, but also by the brain. Fat-adapted athletes have reported far more mental clarity after intensive exercise – in contrast to the mental fog often described by athletes after endurance workouts (3).  

At the Low Carb Clinic, we can help you optimise your diet for improved energy, endurance and performance – and cut out the need for high-sugar, expensive supplements to get you through race day.

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1. Venables, M., Achten, J., & Juekendrup, A. (2005). Determinants of fat oxidation during exercise in health men and women: a cross sectional study. Journal of Applied Physiology, 98, 160-167. doi:doi:10.1152/japplphysiol.00662.2003

2. Volek, J. (2015, July). Nutrition for optimising athletic performance. Retrieved from YouTube: https://www.youtube.com/watch?v=tQbgdRoAfOo

3. Volek, J., Noakes, T., & Phinney, S. (2014). Rethinking fat as a fuel for endurance exercise. European Journal of Sports Science. doi:http://dx.doi.org/10.1080/17461391.2014.959564

4. Evans, W., & Hughes, V. (1985). Dietary carbohydrates and endurance exercise. American Journal of Clinical Nutrition, 41, 1146-1154.

5. McSwiney, F., Wardrop, B., Hyde, P., Lafountain, R., Volek, J., & Doyle, L. (2018). Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes. Metabolism Clinical and Experimental , 81, 25-34. doi:https://doi.org/10.1016/j.metabol.2017.10.010

6. Vogt, M., Puntschart, A., Howald, H., Mueller, B., Mannhart, C., Gfeller-Tuescher, L., . . . Hopeeler, H. (2003). Effects of dietary fat on muscle substrates, metabolism, and performance in athletes. Medicine and Science in Sports & Exercise, 952-960. doi:DOI: 10.1249/01.MSS.0000069336.30649

7. Evans, W., & Hughes, V. (1985). Dietary carbohydrates and endurance exercise. American Journal of Clinical Nutrition, 41, 1146-1154.

8. Volek, J., Freidenreich, D., Saenz, C., Kunces, L., Creighton, B., Bartley, J., . . . Phinney, S. (2016). Metabolic characteristics of keto-adapted ultra endurance runners. Metabolism, 65, 100-110. doi:http://dx.doi.org/10.1016/j.metabol.2015.10.028