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Common nutrition issues for marathon runners

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Are you planning on running a marathon?

There are some common issues that marathon runners face.

  1. Not fuelling enough at the start or not fuelling correctly throughout the race
  2. Gastrointestinal issues (stomach issues) which can either be from the act of running itself or trying new foods that they didn’t practice during training for the event
  3. Hydration issues either from not being hydrated or drinking too much


Preparing starts days before and not just on the day of the race. Earlier ‘carb loading’ protocols used to be extreme which had some negative side-effects. This involved having a very intense workout a week before the race and then restricting carbohydrates (to deplete glycogen) for 3 days and not exercising. However, this can impact on recovery and has also been found to lead to stomach issues.

A more moderate protocol was then introduced which involves tapering training towards the race whilst gradually increasing carbohydrate intake (to increase glycogen concentrations). Well trained individuals may be able to achieve this with just 1-2 days of carb loading along with reduced training.

Basically, you should start the race with sufficient muscle glycogen but stores don’t need to be excessively high. In fact, extremely high stores means glycogen is broken down faster.

Pre-race meal – as part of the pre-race meal the recommended range of carbohydrates to be included in the pre-race meal is 1 – 4g per kg carbohydrates. 100-200 g carbs would be sufficient 1-4 hours before exercise. This is to top up liver glycogen before the race. Ideally you should avoid foods that are going to potentially give you stomach issues, so avoiding high fat and fibre foods is best.


Dehydration can reduce performance. On the other hand, drinking too much can lead to hyponatremia (low sodium in the body), which is a serious condition (but rare).

Estimating your sweat losses means you have an idea of how much you sweat and subsequently how much you need to drink. You can measure sweat rate by using a calculation (weighing yourself before and then after training and then correcting the weight loss for the amount of fluid you have consumed).  A little bit of weight loss is natural after a marathon but shouldn’t be losing over 2%, and gaining weight indicates a person has drank too much fluid which can be very dangerous.

Stomach issues

Trying new products on race day is a big no-no. You should have practiced your nutrition plan during your training for the event and it should be the same on race day. However, it’s also common for people to try and stick rigidly to a plan even when experiencing stomach issues. If you experience stomach issues during a race, it may be that you need to slow your pace for a while or take on less food until it passes

‘nutrition training’ should actually start around 6-12 weeks in advance of a marathon

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