The Importance of Adequate Carbohydrate Intake
Blog by: Katie Duong, 2022 Undergraduate Summer Research Student
Why does Carbohydrate Availability Matter for Athletes
Endurance sports rely primarily on the aerobic system, which requires adequate delivery of oxygen and availability of carbohydrates (CHO) and lipids. CHO requires less oxygen to break down for fuel than lipids, therefore carbohydrates are an effective
energy source during endurance exercise. Low CHO availability can limit performance in higher intensity endurance exercise. Consuming sufficient CHO before and during training or competition allows athletes to sustain high rates of carbohydrate oxidation. This supports motor recruitment, pacing, and perception of effor
t (Burke, 2021).
Carbohydrates and Energy
Underfueling is known to be associated with the female athlete triad (*link blog post) and RED-S (*link blog post). This reduction in energy availability is caused by an imbalance between energy expenditure and energy intake. One consequence of low energy availability and RED-S is the body’s inability to fully recover from workouts. This can lead to negative outcomes from training-overload or misdiagnosis of overtraining syndrome (Stellingwerff et al., 2021). When thinking about low energy availability, it is especially important for athletes to consider carbohydrate intake. Overall energy deficits are most often due to low or inadequate carbohydrate intake (Cook and Haub 2007). Furthermore, recent research has shown that low CHO availability may lead to RED-S symptoms, even if the athlete is meeting their overall energy needs (Stellingwerff et al. 2021).
Carbohydrates and Bone Health
Short-term low CHO high fat diets have been shown to increase bone breakdown after exercise, even if an athlete has adequate energy intake (Heikura et al., 2019). Chronically low carb intake could result in poor bone (*link to bone health article) health long-term.
Carbohydrates and Hormones
Carb availability has also been shown to affect hormones in the female athlete including: luteinizing hormone (helps control the menstrual cycle), T3 (plays an important role in controlling metabolism), and leptin (main role is to regulate long-term balance between body’s food intake and expenditure) (Stellingwerff et al., 2021). These hormones have been associated with Triad outcomes in prior research.
Daily Carbohydrate Needs
Guidelines recommend 5-10g/kg/day of carbs for general training needs (Burke et al. 2001). However, endurance athletes have an increased need for carbs at around 7-10g/kg/day (Burke et al. 2001). It is important to note that carb needs will vary with training volume and intensity as well as individual needs. Work with a registered dietitian to best tailor this to your unique body.
The Debate around Carbohydrate and Fat Intake
It has been hypothesized that a low carb high fat diet (LCHF) may improve endurance performance by improving the body’s ability to use fats as muscle fuel, sparing muscle glycogen (Cook and Haub 2007). However, research has shown that a LCHF diet increases the oxygen cost of walking/running and seems to compromise the body’s ability to sustain high-intensity exercise compared to diets with higher carbohydrate consumption (Burke et al. 2017). A LCHF diet may impair the muscle’s ability to use and restore glycogen, therefore limiting performance of higher intensity endurance exercise (Burke, 2021). Additionally, it should be noted that these effects of a LCHF diet may have a greater impact on female athletes.
Stellingwerff, T., Heikura, I.A., Meeusen, R. et al. Overtraining Syndrome (OTS) and Relative Energy Deficiency in Sport (RED-S): Shared Pathways, Symptoms and Complexities. Sports Med 51, 2251–2280 (2021). https://doi.org/10.1007/s40279-021-01491-0
Heikura IA, Burke LM, Hawley JA, et al. A short-term ketogenic diet impairs markers of bone health in response to exercise. Front Endocrinol (Lausanne). 2019;10:880.
Burke, L.M. (2021), Ketogenic low-CHO, high-fat diet: the future of elite endurance sport?. J Physiol, 599: 819-843. https://doi.org/10.1113/JP278928
Burke, L. M., Cox, G. R., Culmmings, N. K., & Desbrow, B. (2001). Guidelines for daily carbohydrate intake: do athletes achieve them?. Sports medicine (Auckland, N.Z.), 31(4), 267–299. https://doi.org/10.2165/00007256-200131040-00003
Burke, L.M., Ross, M.L., Garvican-Lewis, L.A., Welvaert, M., Heikura, I.A., Forbes, S.G., Mirtschin, J.G., Cato, L.E., Strobel, N., Sharma, A.P. and Hawley, J.A. (2017), Low carbohydrate, high fat diet impairs exercise economy and negates the performance
Cook, C.M., Haub, M.D. Low-carbohydrate diets and performance. Curr Sports Med Rep 6, 225–229 (2007). https://doi.org/10.1007/s11932-007-0036-5
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