Low Carb Training: Should you do it?

Most cyclists are familiar with eating a lot of carbs.   In simple terms, “Carbohydrate is the most important nutrient in an athlete’s diet because it is the only fuel that can power intense exercise for prolonged periods…” [1], [2]. 

If “high carb” is the evidence-based choice for optimal performance [19], why are so many cyclists talking about restricting carbohydrate?  Before we jump into low-carb training, let’s make the case for why carbohydrate is essential for cyclists.

The Case for Carbs

During easy riding ( ≤40% of max) fat supplies the majority of your energy, but as ride intensity increases, the balance begins to shift increasingly in favor of carbs [3].

Check out the image below to see how fat/carb metabolism shifts as a product of exercise intensity.

If you take anything from the image above, it should be an understanding that if your cycling goals include riding hard for even a short amount of time (like any bike race or group ride ever), consuming adequate carbohydrate is crucial for attaining your best performance [4], [5].  So how many carbs should you be eating?

Carb Recommendations

Historical recommendations for cyclists focused on promoting a general carb ratio of roughly 50-70% of your diet [1].  Since cyclists are often riding at high intensities, going  “high carb” all the time made logical sense [6], [7].  But as our understanding of carb metabolism has evolved, so has the precision of carbohydrate recommendations.

Current guidelines for cyclists center around “High Carbohydrate Availability”, a strategy that seeks to match the specific fuel demands of a training session, with onboard glycogen stores (endogenous) and carb fueling (exogenous) during exercise [6, 8].

For a more in-depth look at high carb availability guidelines check out our post on getting lean.   With high carb firmly in context, let’s shift gears to training low.

The Case for Restriction

Low-carb training “is a general term to describe training with low-carbohydrate availability.  This low-carbohydrate availability could be low muscle glycogen, low liver glycogen, low-carbohydrate intake during or after exercise, or combinations thereof” [12].

Recent research suggests that training with either low glycogen stores or in a fasted state can help to activate key cell signaling proteins which over a chronic training period may increase a cells capacity to utilize oxygen, increase fat metabolism and potentially improve cycling performance [6], [9]–[11].  So how exactly is “low carb” done?

In the image below we break down two common strategies used to train low.

Should you do it?

So what’s the deal, should you begin to incorporate low-carb sessions in your training?  Maybe, but before you do, it’s important to highlight several of the potential downsides.  Training low carb:

• Forces a reduction in training intensity. If you’re unable to train hard you may not be able to train hard enough to improve [15].
• Increases RPE [6], in other words, it’s more psychologically demanding.
• May make you more susceptible to illness [16]. Obviously getting sick craters your fitness.
• Can lead to a loss of muscle mass [17].
• Can impair your ability to oxidize carbs. In other words, you use it or lose it when it comes to optimizing carb metabolism (think race day fueling) [18].

Periodized Nutrition

Alright, high carb or low carb, which strategy makes the most sense?  Ultimately if you’re committed to experimenting with low carb training make sure not to trade in your high carb toolbox.

In practical terms this means on some days, for some workouts, you may choose to follow a low carb training strategy, while on other days, for specific workouts, you follow a high carbohydrate availability strategy.  By definition, this approach to fueling is called periodized nutrition [12].

Periodized nutrition is the “planned, purposeful, and strategic use of specific nutritional interventions to enhance the adaptations targeted by individual exercise sessions or periodic training plans, or to obtain other effects that will enhance performance longer term” [12].

Smart low carb training involves a larger periodized nutrition plan and doesn’t abandon high carb availability strategies, got it.  Where do we go from here?

A few suggestions

If you’re intrigued by the potential for free speed with less carbs and are comfortable with the potential downsides listed above, here are a few suggestions going forward.

• Before you experiment with any low carb training, make sure you have the basics of “high carbohydrate availability” absolutely dialed.  Start with mastering exactly how to fuel for each of your rides then add the ability to flex your overall carb intake from day to day based on your energy demands.
• Are you struggling with the basics of training like consistency and progressive overload?  Skip the low-carb stuff and focus on the basics.
• Do you have the discipline to tightly program your workouts in conjunction with a low-carb nutritional strategy?   A haphazard approach is likely to cause more harm than good.
• Are you highly motivated, disciplined, and have all the other basics of training nailed down?  Give it a shot but make sure to stay centered within the larger context of a periodized nutrition plan (i.e. don’t forget that carbs are essential for maximal performance).  You might just earn some free speed while spending less money on pasta.

References

[1]      E. F. Coyle, “Timing and method of increased carbohydrate intake to cope with heavy training, competition and recovery,” J. Sports Sci., vol. 9, pp. 29–51, 1991.
[2]      J. A. Romijn et al., “Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration,” 1993.
[3]      G. A. Brooks, “IMPORTANCE OF THE ‘CROSSOVER’ CONCEPT IN EXERCISE METABOLISM,” Clin. Exp. Pharmacol. Physiol., vol. 24, pp. 889–895, 1997.
[4]      H. Keizer, H. Kuipers, G. van Kranenburg, and P. Geurten, “Influence of Liquid and Solid Meals on Muscle Glycogen Resynthesis, Plasma Fuel Hormone Response, and Maximal Physical Working Capacity*,” Int. J. Sports Med., vol. 08, no. 02, pp. 99–104, Apr. 1987.
[5]      L. M. Burke et al., “Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers.,” J. Physiol., vol. 595, no. 9, pp. 2785–2807, May 2017.
[6]      L. M. Burke, J. A. Hawley, A. Jeukendrup, J. P. Morton, T. Stellingwerff, and R. J. Maughan, “Toward a common understanding of diet-exercise strategies to manipulate fuel availability for training and competition preparation in endurance sport,” Int. J. Sport Nutr. Exerc. Metab., vol. 28, no. 5, pp. 451–463, Sep. 2018.
[7]      D. T. Thomas, K. A. Erdman, and L. M. Burke, “Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance,” J Acad Nutr Diet, vol. 116, no. 3, pp. 501–528, 2016.
[8]      L. M. Burke, J. A. Hawley, S. H. S Wong, and A. E. Jeukendrup, “Carbohydrates for training and competition,” J. Sports Sci., vol. 29, pp. 17–27, 2011.
[9]      S. G. Impey et al., “Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis,” Sport. Med., 2018.
[10]    J. D. Bartlett, J. A. Hawley, and J. P. Morton, “Carbohydrate availability and exercise training adaptation: Too much of a good thing?,” Eur. J. Sport Sci., vol. 15, no. 1, pp. 3–12, 2015.
[11]    J. A. Hawley, C. Lundby, J. D. Cotter, and L. M. Burke, “Maximizing Cellular Adaptation to Endurance Exercise in Skeletal Muscle,” Cell Metabolism, vol. 27, no. 5. 2018.
[12]    A. E. Jeukendrup, “Periodized Nutrition for Athletes,” Sport. Med., pp. 1–13, 2017.
[13]    A. K. Hansen et al., “Skeletal muscle adaptation: training twice every second day vs. training once daily,” J Appl Physiol, vol. 98, pp. 93–99, 2005.
[14]    L. A. Marquet et al., “Enhanced Endurance Performance by Periodization of CHO Intake: ‘Sleep Low’ Strategy,” Med. Sci. Sports Exerc., 2016.
[15]    C. J. Hulston et al., “with Low Muscle Glycogen Enhances Fat Metabolism in Well-Trained Cyclists,” Med. Sci. Sport. Exerc, vol. 42, no. 11, pp. 2046–2055, 2010.
[16]    M. Gleeson, D. C. Nieman, and B. K. Pedersen, “Exercise, nutrition and immune function,” J. Sports Sci., vol. 22, no. 1, pp. 115–125, Jan. 2004.
[17]    K. R. Howarth, S. M. Phillips, M. J. MacDonald, D. Richards, N. A. Moreau, and M. J. Gibala, “Effect of glycogen availability on human skeletal muscle protein turnover during exercise and recovery,” J Appl Physiol, vol. 109, no. 2, pp. 431–438, 2010.
[18]    G. R. Cox et al., “Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling,” J. Appl. Physiol., vol. 109, no. 1, pp. 126–134, Jul. 2010.
[19]  J. W. Helge, “A high carbohydrate diet remains the evidence based choice for elite athletes to optimise performance,” J Physiol, vol. 595, no. 9, p. 2775, 2017.