Training in a fasted state – pros & cons

Does training in a fasted state without using sports drinks or gels improve endurance performance?


Reproduced by kind permission of Andy Dubois

I am often asked if sports drinks and gels are worthwhile. Are they necessary on a long run? Running on an empty stomach has got to improve the ability of the body to burn fat doesn’t it?

The research from a number of studies on this is fairly conclusive.

The good news

Training on an empty stomach without additional carbohydrates WILL increase fat oxidation.

The bad news

If however before your race you have a pre-race meal and drink sports drink or consume gels or bars during the race then your ability to oxidise fat is no better than someone who drank sports drink during their training runs.

More bad news

Training in a fasted state and without consuming additional carbohydrate’s means you won’t be able to run as fast in training. To break down fat you require more oxygen and it takes longer to break down so therefore you have to run slower. Admittedly your pace will improve as your body becomes more efficient at breaking down fat but you would still be able to run faster using sports drink or at least having breakfast.

Your training should reflect your race

Your body adapts to the specific demands placed on it in training. So if your race involves competing on an empty stomach with no possibility of additional carbohydrates then training in a fasted state is very beneficial. If your race allows you to have some form of breakfast and has the means of providing you with sports drinks, gels or other food during the race why would you train to become more efficient at not having this?

What about if I run out of energy between aid stations? Will training fasted help then?

If you start to run low in energy and its a few miles till the next aid station to top up your supplies will all that training in a fasted state help you know? I wasn’t able to find any studies at all on this scenario and it’s quite possible that it may help. But if this happens it means you didn’t plan your nutrition very well during the race and you’d be better off giving more thought to organising your nutritional strategy.

Surely it can’t hurt to run in a fasted state?

Remember that running in a fasted state means you have to run slower than if you consumed carbohydrates. All of us instinctively know this which is why we’d never fast before a big race and avoid sports drinks and gels during the race (I’m sure there are some notable exceptions to the rule but that’s all they are – exceptions).

So lets say you can run your long run of say 20 miles at 9 min mile pace in a fasted state and when you have breakfast and have gels you can manage 8.45 min miles . Assuming you did this long run each weekend for around 3 months before your race. That means you would have run 260 miles of long runs. So you’ve run 260 miles at a pace 15 seconds per mile slower than you could have run if you’d consumed carbohydrates. That’s a lot of miles running at a slower pace. Yes your long run is meant to be easy but running at 8.45 min mile would feel no harder than running 9 min miles if you’ve eaten.

Of course this is a made up example and there are no studies I’ve seen that prove there is this much difference between the two but the fact is you cannot run as fast in a fasted state compared with ingesting a steady stream of carbohydrates.

What about if I need to drop a few pounds to reach optimal race weight?

Exercising at a low intensity for a long period of time is sometimes recommended to lose fat as it burns the biggest percentage of energy from your fat stores. Percentages don’t really matter though as the overall energy cost is low so a large percentage of a low amount doesn’t add up to much.

What is important is what is going to boost your metabolism. Since you can only exercise for so many hours per week surely it makes more sense to see if you can boost your metabolism during the hours you are not exercising. Even if you exercise for 2 hours a day that still leaves 22 hours a day you aren’t.

Best way to boost your metabolism?

High intensity interval training is a proven way to not only boost your metabolism but also improve your endurance . Interval training improves lactate tolerance, increases aerobic endurance, boosts your metabolism and increases running efficiency. It should be a part of every runners routine.

The Verdict

Many years ago it was thought that you could train yourself to cope without water during a run by practising not drinking in training. That has long since been disregarded. Now we’ve moved to practising not drinking sports drinks. Hopefully people will realise that their training and consequently their racing would be much improved if they had a small breakfast and consumed some carbohydrates during their long run.

People will argue that they have never had sports drink and they run a very fast marathon and in fact Haile Gebrselassie apparently drank nothing but water in one of his marathons. Just because someone can perform well without sports drink doesn’t mean they can’t perform better with sports drink! In Gebrselassie’s case an elite athlete can store enough carbohydrates for around 2 hours of running at around 85% of maximum heart rate. Running a marathon in 2 hours and 4 minutes allows him to get away with only drinking water. The rest of us aren’t so lucky!