Train Low, Compete High -- Does It Work?

Low-Carb Training and High-Carb Competing

Female runners
Training low or high?. Thomas Barwick/Taxi/Getty Images

If you have not heard of this much touted training technique, here's how it is supposed to work.

The idea of 'train low, compete high' is that you train selectively with low reserves of carbohydrate to enhance fat burning responses and then initiate full carbohydrate (glycogen) re-fuelling close to competition time. Initially, the idea was to apply mostly to endurance athletes like marathoners and triathletes but in more recent times it has been suggested for any activity that lasts for an hour or more, including team sports.

The idea is that prior to training a few times each week you don't eat, or eat or drink minimally in the hours before your training run or even your track or gym session.

This is supposed to train your body, to some extent, to utilize fat stores and to further adapt to the biochemical and fuel status that one might experience under stressful competition. The idea is to maximise both fat and glycogen use in competition. The 'train low' part refers to training depleted in carbohydrate fuel, and the 'compete high' part means competing in a fully refuelled condition as one might do when carb loading prior to a marathon.

Does It Work?

The answer to that question is two-fold. Yes, there is little doubt that training in a low-carbohydrate state will adapt muscle to utilize fat more efficiently and perhaps save precious glycogen for when it is needed most -- high intensity performance. However, there is little scientific evidence that such a strategy improves measured performance for most sports compared with a standard high-carbohydrate training protocol.

The Dangers of TLCH

Too much adaptation to fat preference can blunt muscle glycogen response at times of high demand like sprinting, hill climbing, heavy lifting, anaerobic effort and similar high-intensity demands. When you overdo the fat adaptation, an enzyme called pyruvate dehydrogenase is down-regulated, which can lead to inefficient retrieval of glucose fuel from stored muscle glycogen.

Fat as fuel. When researchers tried high-fat eating for athletes, they found that the body did adapt to an increase in fat consumption by prioritizing fat use as body fuel. However, the downside of this was that even when they ensured sufficient carbohydrate was stored for high-intensity exercise, the "rate" at which glucose was available to muscle had been depreciated. That is, the high-fat diet had actually slowed down the athlete for activities that required a lot of instant power -- like a sprint finish or accelerating up a hill in a bike race. Weight lifting has similar, high-power requirements. You want that glucose (carbohydrate energy) available as fast as possible. (The only faster fuel is phosphocreatine, which only last for ten seconds or so.)

Immunity Compromised. High volumes of training, especially high-intensity training, can adversely affect your immune system. Adequate carbohydrate helps to maintain immunity by preventing a build-up of the hormone cortisol. Cortisol is induced in a low-carbohydrate state to maintain blood glucose.

It does this by a process called gluconeogenesis.

Protein as fuel. Compared to carbohydrate (glucose) and fat, protein is not a major fuel source even though it can be broken down into glucose, which can be used for fuel when other sources run low. However, this is an inefficient pathway to glucose. Another key point to consider is that when liver or blood glucose gets low, your own muscle will be broken apart -- first into amino acids, then to glucose. Your body knows that it must protect your blood glucose at all costs, or else you can faint from hypoglycemia, just like a diabetic. Muscle, in a way, is a permanent storage site of available glucose. If you want to protect muscle from this process, then you need to have adequate glucose (carbohydrate) available from other sources to prevent muscle being broken apart. A low-carb diet makes you more susceptible to this degradation of muscle, although careful exercise planning and nutrient cycling might make this less likely.

How Training Low Might Inhibit Strength and Muscle Building

In a comparative study, two groups of novice weight trainers were followed. Subjects were randomly assigned to a low carbohydrate (3.4 g/kg), higher protein diet (1.5 g/kg); or a high carbohydrate (5.0 g/kg), lower protein diet (1.2 g/kg). Both diets exceeded the recommended protein intake. (The low-carb group works out to less than 40% carbohydrate energy.)

In the results, the low-carbohydrate group had a greater strength loss after exercise compared to the high-carb group. The low-carbohydrate exercisers also had less efficient use of protein for muscle repair and rebuilding after training. The authors concluded that dietary carbohydrate, compared to protein, may be a more important nutrient to the novice weight lifter when recovering from exercise-induced muscle damage.

Summing up: If you're on a weight-loss diet, removing refined carbs and sugars is always a good approach, but going too low-carb in your training is a delicate balance of adverse effect and positive results. For heavy exercisers, a low-carb diet is likely to impair your best performance -- in training and probably also in competition.


Stellingwerff T, Spriet LL, Watt MJ, et al. Decreased PDH activation and glycogenolysis during exercise following fat adaptation with carbohydrate restoration. Am J Physiol Endocrinol Metab. 2006 Feb;290(2):E380-8.

Benjamin L, Blanpied P, Lamont LS. Dietary Carbohydrate and Protein Manipulation and Exercise Recovery in Novice Weight-Lifters. JEPonline 2009;12 (6):33-39.

Nestle Nutr Inst Workshop Ser. 2011;69:19-31; Altering endogenous carbohydrate availability to support training adaptations. Philp A(1), Burke LM, Baar K.

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