Can a Low Carbohydrate Fuel Strategy Improve Performance?

For years athletes have tinkered with ways to manipulate fueling strategies for training adaptations and to maximize performance. There are a number of fueling strategies that claim to do just this. One of the newer training fueling strategies is to train-low; meaning train with low to no carbohydrates. Why you ask?

Let’s take a look at why the train-low fueling strategy may have potential for boosting your performance. The train-low concept is founded on the hypothesis that if you restrict carbohydrates (CHO) availability before, during and after training it will enhance performance by….

  • Improving the ability of your muscles to use oxygen, prolonging fatigue
  • Increasing lipid oxidation, resulting in the ability for your body to burn fat for fuel at higher intensities and thus preserving glycogen stores
  • Increasing mitochondrial adaptation allowing the powerhouses of your cell to produce more energy
  • Enhancing muscle protein synthesis, the rebuilding of muscle that is broken down during exercise

How do you implement a train-low strategy? There is more than one way to apply the train-low strategy, but the methods that have been researched include:

  • Training in a fasted state -- fasting overnight followed by training in the morning on an empty stomach
  • Training twice a day (it is difficult to completely replenish your glycogen stores when you train twice a day)
  • Low-sleep -- intensity training in the evening followed by fasting overnight and training in the morning on an empty stomach

This may all sound great, but before you jump on the train-low bandwagon, it might be helpful to know if there is any proof in the pudding. In other words, does it work. A number of research studies to date have demonstrated that implementing a train-low strategy does have some validity, whereas other studies have not shown any benefits for trained athletes nor for endurance athletes. A recent study illustrated that the train-low fueling strategy was not effective in improving performance of trained athletes. In fact, changes in performance, resting muscle glycogen levels (your stored fuel), and mitochondrial adaptations were similar between the group consuming high CHO and the group using the train-low strategy (1).

In a few studies, mitochondrial adaptation (the efficiency of your mitochondria) was improved, but the subjects were untrained individuals. Thus, this begs the question if the adaptation was due to the training regimen or due to low CHO consumption. The unpredictable results of the train-low studies are most likely due to lack of standards causing too much variability to draw a conclusion that the train-low program actually works, especially with trained athletes.

Something else to consider is that the train-low strategy can result in unintended loss in total body mass in both muscle and fat. For athletes trying to lose weight, the train-low strategy could be beneficial with the caveat that muscle protein synthesis (repairing of muscles) may be inhibited. In a study comparing muscle protein synthesis between a high CHO group and a train-low CHO group of endurance athletes resulted in a significant reduction of muscle synthesis post exercising in the train-low group (2).  

With all this being said, there may be a place for training with low CHO and a time when adequate CHO consumption is required to maintain performance and post-exercise muscle rebuilding. For some, it may be possible to use a train-low strategy on training days that don’t include high intensity at prolonged duration and instead be used on days in which low CHO will not compromise performance, such as steady-state, below lactate threshold training days. This type of strategy may be beneficial in inducing work-efficiency (increasing the efficiency of your mitochondria). Whereas on days when sustained duration and high workload is required, adequate CHO should be consumed 24-hours prior, during and after training session as not to impede performance and muscle protein synthesis.

Keep in mind that your individual response to a combined CHO fueling strategy may be different than your training partner and may not deliver the intended results you are seeking. Gender differences in metabolism also needs to be taken into consideration. Furthermore, utilizing a train-low strategy for an extended period of time has not been studied, but it is known that performance will suffer when glycogen stores are depleted for an extended period of time. In fact, failure to daily replenish glycogen stores increases the rate of muscle fatigue, resulting in subpar training sessions and races and increases your risk of injury (3).

Still interested in trying the train-low strategy? If so, it’s well advised to work one-on-one with sports nutritionists that understand fueling techniques in order to achieve optimal performance.

Contact us to learn more about implementing fuel strategies for performance.



(1) Gejl, K. D., Thams, L. B., Hansen, M., Rokkedal-Lausch, T., Plomgaard, P., Nybo, L., ... & Vissing, K. (2017). No Superior Adaptations to Carbohydrate Periodization in Elite Endurance Athletes. Medicine and science in sports and exercise, 49(12), 2486-2497.

(2) Impey, S. G., Hammond, K. M., Shepherd, S. O., Sharples, A. P., Stewart, C., Limb, M., ... & Close, G. L. (2016). Fuel for the work required: a practical approach to amalgamating train‐low paradigms for endurance athletes. Physiological Reports, 4(10).

(3) Ørtenblad, N., Westerblad, H., & Nielsen, J. (2013). Muscle glycogen stores and fatigue. The Journal of physiology, 591(18), 4405-4413.