Fasted Training

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Fasted training for performance excellence

Endurance athletes have tended to consume a diet very high in carbohydrates. Fat and protein have typically taken a ‘back seat’, and carbohydrates – viewed as the primary energy source for high intensity endurance performance – were the cornerstone of one’s dietary planning.

In recent years, however, there seems to have been a slight shift in the hierarchy of these macro-nutrients, in regard to the athlete’s training/performance needs, and ultimate goal of performance improvement. For example, the awareness of the role that protein plays in lean tissue & muscle maintenance is more widespread, and endurance athletes appear to be increasing their daily intake of protein. In addition, fat appears far more widespread in endurance circles; occasionally to the extent that fat is now being consumed in similar quantities that carbohydrates used to back in the 80’s & 90’s. These trends and shifts in athletic communities have meant that we now have a diverse array of dietary compositions: those that follow a very low fat approach, those that only consume ‘healthy fats’ and those that consume a very low-carb/high-fat diet (among others).

There’s no doubt that individuals have performed incredibly well on all different types of diets, which most probably reflects genetic differences in combination with a sufficient training stimulus to help these genes blossom. What if, however, there’s a more moderate approach that promotes ‘the best of both worlds’; that gets the benefit of greater fat metabolism and optimum carbohydrate metabolism?

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Training fasted

fasted trainingOne method that may promote physiological and metabolic changes beneficial to performance is fasted training. In this context, training fasted would mean, after an overnight fast where one is asleep, commencing morning training without having eaten breakfast. The athlete most probably has sufficient carbohydrate/glycogen stores anyway, given a balanced dinner and overall nutrient intake the day before. They then commence training with muscle glycogen stores present, most likely absent only the liver glycogen stores used to maintain blood glucose overnight. But essentially they commence training without any ‘exogenous’ carbohydrates i.e. without consuming any food or drink containing carbohydrates, before or during training.

Various studies have shown that there appears to be an increase in the ‘machinery’ responsible for improved fat oxidation (fat burning) after a period of training fasted. At the same time, it appears as though there is no decrease in the machinery responsible for carbohydrate metabolism, which would perhaps occur on a long-term low-carbohydrate, high-fat diet (often seen as the way to promote fat metabolism). As we know, carbohydrates are very necessary for performance, and permit one to exercise at very high intensities in particular (where fat metabolism has limitations). Going on a chronic high-fat diet, which would by definition be low in carbohydrate, would hinder performance due to reductions in the processes required to burn carbohydrate for energy at very intense activities.

Key point: promoting great fat burning capabilities can be achieved by a higher fat diet. However, chronically high fat may lead to a decline in the ability to utilise carbohydrates. One way to perhaps achieve both would be fasted endurance training.

In addition, fasted training appears to slow down the decline in muscle glycogen stores during performance, potentially demonstrating a glycogen sparing effect. This would appear beneficial in delaying the time to fatigue (come race day), which would otherwise hinder performance. In effect, after a period of fasted training where one has completed a number of sessions without pre exercise nutrition (or modified nutrition), come performance – and in a situation where one ‘does’ consume carbohydrates during the race perhaps – the body appears to save more of the stored muscle glycogen, potentially then delaying the time to fatigue.

How to increase endurance

It appears as though physiological and metabolic changes take place when one completes training fasted, before consuming carbohydrates, which leads to changes not attained by those eating the same diet yet exercising after breakfast. Where this actually translates to performance improvements is still yet to be elucidated, and studies so far appear only to show the adaptations that occur as opposed to clear performance effects. However, the physiological and metabolic changes that take place – in the acute phase after training – suggest that should they be added together over the long term, perhaps performance improvements are realistically achievable.

Fasted Training summary

Always training after having eaten may be sub-optimal. Taking part in some form of training in a ‘fasted’ state may be another method to enhance performance through adaptations to the body. Physiological and metabolic changes appear to take place when an individual’s exercises before consuming an energy source that don’t occur when additional carbohydrates are consumed. What’s more is that training intensity doesn’t appear to be significantly hindered in the fasted state. These changes, over the long term, may serve to improve performance. Chronically high fat diets would appear unnecessary, particularly in light of evidence that suggests a diet low in carbohydrates negatively affects carbohydrate metabolism. Fasted training appears one way to achieve more efficient fat metabolism, whilst the ability to burn carbohydrates remain intact.

For further reading, please see:

Stannard et al. (2010). Adaptations to skeletal muscle with endurance exercise training. Summary: metabolic changes took place after a period of endurance training, more so in the group that trained fasted compared to those who trained fed. Untrained males and females respond differently to fasted or fed training. Men responded better to fasted training than women.

De Bock et al. (2008). Effect of training in the fasted state on metabolic responses during exercise with carbohydrate intake. Summary: when diets are the same, and some train after breakfast and some train before breakfast, those who train before breakfast stand to gain additional, beneficial, performance adaptations