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Training Low Carbohydrate? Not So Fast

Gazelle Nutrition Lab / Blog  / Training Low Carbohydrate? Not So Fast

Training Low Carbohydrate? Not So Fast


training low carbohydrate with only water

Training low carbohydrate has been making its way into the potential nutritional arsenal for athletes. Like all athletic endeavours, training for an endurance event requires time and planning. The goal is to balance training, mental stressors, sleep, nutrition, and sometimes injury to optimize performance on competition day. Nutrition is one small piece of this puzzle but can make all the difference.

Training Low Carbohydrate?

When you train, some days you train hard and others not so hard so that your body and muscles learn to adapt in ways that may be of benefit on race day. You can do the same with your diet. As with training, you can manipulate your nutrient availability to hone your body’s ability to efficiently use fuel over the range of intensities that commonly makes up an endurance event. One such concept is training with low carbohydrate availability in an attempt to improve your muscle’s capacity to use fat as fuel.

Exercise Fuels

Exercising muscle needs fuel. The availability of this fuel, or nutrients, determines endurance training capacity and performance. During exercise, we use a combination of carbohydrate and fat and some protein. While high carbohydrate availability results in better performance in most people, being able to use fat for fuel efficiency is also important.

Our glycogen stores are limited. On the other hand, even in lean people, our fat stores are relatively vast and so if we can adequately harness them this would alleviate the pesky need to consume carbohydrate during long events.

And so was born the concept of training with low carbohydrate availability to enhance fat metabolism pathways but competing with high carbohydrate availability to facilitate optimal performance when it was needed.

What About High Fat?

Research into this idea has looked at changing the diet as a whole, for example to a high fat, low carbohydrate diet or modifying carbohydrate availability through training patterns. At this point, the body of evidence seems to indicate that low-carb high-fat diets are not helpful for optimal athletic performance.

In a 2008 study out of RMIT University in Melbourne, Australia, researchers used endurance-trained male cyclists to show that after just five days on a high-fat diet, followed by one day on a high carbohydrate diet; the exercising muscle can use more fat and spare glycogen (1). Fantastic right? Not so fast.

A follow-up study did not translate into enhanced performance. It appears that this diet may come at a cost. The muscle becomes less efficient at using carbohydrate and cannot respond sufficiently to the metabolic demands of sprints and high-intensity efforts that occur in races, even in long races. It seems the low-carb high-fat diet is taking away the athletes ability to gear up their effort as needed.

Training Low vs. Sleeping Low

Most recent research has focused on limiting carbohydrate around key training sessions (“train low”). For example, an athlete might have two training sessions on the same day. During the first, they deplete their glycogen stores, and they do not replace them before the second session. An athlete could also wake up and without eating carbohydrate go for an early morning training session.

Alternatively, an athlete can “sleep low” by training in the evening and eating a low carbohydrate meal before bed. One of the main problems with these approaches is that they impair the athlete’s ability to complete their next workout at their usual intensity.  There is less carbohydrate available for high-intensity efforts and exercise is perceived to be harder in times of low carbohydrate availability (2).  As such, this type of intervention has met with mixed results and is not clearly advantageous at this point.

The Lowdown

At this time, training with low carbohydrate does not appear to benefit performance. You should recognize, though, that most of us inadvertently modulate the way we eat due to the demands of everyday life. Some days we eat well before and after we exercise, and other days not so much. So, it is possible that these studies are not picking up on metabolic changes that have already occurred or that are always evolving.

In a nutshell, though, on most days you should try to eat more carbohydrate when you are training hard and less when you are not. Eat according to exercise needs and your performance will follow.

Even so, if you would like to try “training-low” plan it carefully into your seasonal or yearly training cycle. Periodize this strategy: incorporate it into your base phase of training once or twice a week but exclude it when your training schedule ramps up.  Limit “training-low” to non-key sessions.  You can also practice a few strategies to help retain your speed and intensity.  Swish with a carbohydrate-containing drink intermittently throughout the session to trick your brain into thinking you have carbs on board; include caffeine in moderation before or during your workout, and maybe add some amino acids or protein to help limit muscle breakdown for fuel.


Nutrition planning is integral to achieve your optimal athletic performance. Gazelle Nutrition Lab delivers one-on-one or group nutrition counselling and consulting to both recreational and high-performance athletes. In addition, the Gazelle Blog is a free resource for healthy recipes and health tips. Have questions? We’d love to hear from you! Get in touch!


  1. Yeo WK, Lessard SJ, Chen Z, Garnham AP, Burke LM, Rivas DA, Kemp BE, Hawley JA. Fat adaptation followed by carbohydrate restoration increases AMPK activity in skeletal muscle from trained humans. J Appl Physiol 105: 1519–1526, 2008.
  2. Yeo WK, Paton CD, Garnham AP et al. Skeletal muscle adaptation and performance responses to once a day versus twice every other day endurance training regimens. J Appl Physiol 105:1462-1470, 2008.




Ashley Leone

Ashley is a Sports Dietitian and Owner of Gazelle Nutrition Lab. Ashley provides nutrition advice and plans to athletes and everyday active people alike. Her goal is to help fuel your inner athlete and put good sense back into eating. Ashley is an enthusiastic and knowledgeable nutrition specialist with over 20 years of experience.

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