Half Marathon: Everything you need to know about Nutrition

Half Marathon: Everything you need to know about Nutrition

The eternal question of many of the runners who jump at doing a Half Marathon and those who want to improve their previous times: What should you eat for a Half Marathon?

Today, half-distance races have increased their popularity, and the attraction to half-marathon distance racing is growing.

It opens the opportunity for many runners to jump from 10 km to half distance. The fundamental difference is not only that the distance is more than double, but the type of training and the intensity and duration of the race varies considerably.

As we detail in this article above on feedback in endurance sports, there are many variables that must be taken into account when planning such a race to perform it successfully.

Basic characteristics of a half-marathon

The official distance is 21 kilometres, more than twice as fast and more intense racing than a 10-kilometer race.

The duration of the race exceeds 60 minutes, and the intensity zones to which it is performed are often different from those of short-distance races. Despite maintaining a high intensity during the race, this intensity is lower than that of a 10 km race.

And at this point, the body, from a physiological point of view, works at a different pace and with energy needs that must be considered to achieve a successful half marathon.

Energetic needs

Energy needs from the 60-minute duration of a training and/or competitive race increase, in order to maintain a given intensity level and keep muscles working efficiently by avoiding fatigue due to lack of energy sources.

In half-distance races such as the half marathon, which runs from 70 minutes to two hours, the body uses both the oxidative metabolic pathway and the glycolytic pathway.

Factor in the importance of how efficient the athlete is in terms of their career economy and energy economy.

Marathon runners

What will be worked on in the training preparatory period.

The right performance in our training and in that popular career in which we are going to participate depends on several factors: of course, the training plan carried in the previous weeks, but also correct feeding and rest.

As training volumes and loads increase, so does macronutrient intake, with the support of supplementation, is necessary for, among others:

  • Being able to assimilate to the training well;
  • Recover the glycogen lost;
  • Restore muscle damage;
  • Recover lost salts and minerals mainly lost through sweat and urine.


The same is true in terms of hydration, and maintaining optimal levels of hydration not only allows the body to function properly, but also prevents the unwanted and devastating effects of dehydration: loss of performance and increased fatigue, among others.

The consequences of not getting well hydrated and eating properly in a competition, or in a long race training, make the recovery and assimilation of the work unattainable.

Diet the week before a Half Marathon

In the days leading up to a race or competition, special attention should be paid to hydration and nutrition.

In principle, if we maintain normal hydration levels, there should not be a problem.

However, in the days before a half marathon, stress levels increase (more nerves are usually present), and you use the bathroom more. Also, if there is a higher consumption of drinks with caffeine, you will urinate more.

Thus, greater electrolyte and water loss occurs.

Urine colour turns out to be a good indicator of how hydration levels are (as clear as possible).

Never experiment on the day of the race

It is common to see athletes who buy sports supplementation the day before the race (gels, bars, energy drinks), without having previously tried them.

Without knowing how your digestive system will tolerate them during the test. Also you may be unaware of the necessary ratio of sugars to the hour per kilo of weight.

This kind of detail has to be tried in previous weeks, taking advantage of the sessions and/or long shoots at the pace of competition or lower, in order to know how this kind of product feel as well as whether our stomach assimilates to them well.

Increase in glycogen levels?

It is common to hear that, the days leading up to an endurance test you must perform what is known as “carbohydrate loading”.

Esto significa un aumento de la ingesta de hidratos de carbono con el fin de restaurar y no vaciar los niveles de glucógeno muscular.

As we saw in the previous article, glycogen is one of the main energy resources and metabolic pathway for long-term exercise, and more in medium- and long-term training and careers.

But it should be noted that it will depend on the type of race to be performed to manage the appropriate amount of carbohydrate intake in the previous days.


That there should be carbohydrate repletion that ensures adequate levels for testing does not mean that there should be an uncontrolled excess of the same.

Ideally a slight increase in carbohydrates between 3-4 days before the endurance test; in this case, a half marathon.

As glycogen will be one of the main fuels during the race.

It should also be taken into account, to avoid excess carbohydrates which, the week and/or days before, the intensity and training loads are considerably reduced.

So there will be no excessive depletion of glycogen levels, which means that there must be a slight HCO load but not an excess. Balance is required.

In the case of women, as we already discussed in the article “Woman and Menstrual Cycle”, you can see here we have good storage of intramuscular glycogen; greater than in men. This must also be taken into consideration.

Fibre intake

It is recommended that you reduce products that contain too much fibre.

We must reduce the intake of greens and fibre especially two days before the trace so that we do not make the digestive tract work too much and have no mishap on competition day.

Replacement isotonic drinks

As we have seen, maintaining optimal hydration levels on test day, is an important fact.

It will also be affected by other aspects such as: ambient temperature, initial water levels, salts and minerals, etc.


In addition to drinking water, we must introduce salt and mineral supplementation, or an isotonic supplement.

So how we hydrate the previous days as I have pointed out above will be very important.

What should you eating during a half marathon?

One of the main objectives is that the runner performs throughout the race and is able to maintain the intensity and pace of the exercise to avoid a state of fatigue that prevents him from maintaining that intensity.

Fatigue will appear when the system is unable to produce ATP at the required speed.

While it is not yet resolved today which biochemical mechanism by which muscle glycogen depression causes fatigue, if we know that the muscle’s inability to maintain ATP synthesis speed in glycogen depression is possible to cause a buildup of ATP and Pi (inorganic phosphorus).

In this type of endurance test, such as the half marathon, which is considered to be prolonged exercise, it can cause hypoglycaemia if there is no good storage of glycogen or if it is emptied.

Food supplie

This one of the most relevant and most observed events in marathon runners, due to poor management of supplementation before and during the half marathon.

Therefore, taking CHO during the test will slow the development of fatigue by slowing the emptying rate of liver glycogen and helping to maintain blood glucose levels.

Therefore, it is recommended to take CHO to avoid that possible blood glucose and glycogen depletion and to be able to maintain intensity levels until the end of the test.

Take gels

Depending on the subject’s experience and competitive rhythms, a CHO gel can be ingested at 50 or 60 min of the race, and a second intake at 90 min (in case of subjects whose duration and test is longer).

It is important to note, that the ideal is that the food supplement is easily ingested and assimilated, avoiding the ingestion of solid form HCO. As the intake and assimilation of these is slower.


In half marathon trials, there are water supply points, isotonic drinks, and gels or bars.

While it is recommended that the athlete be the one who carries their own gels, previously tested, should not forget that they must maintain certain levels of hydration; therefore the water/isotonic intake must also be carried out (small sips).

What should you do after a Half Marathon?

As we pointed out in the previous article on Nutrition in Resistance Sports, the recommended thing in the minutes after the end of the half marathon is to take:

Protein and Carb Combinations

To help with the depletion of glycogen levels as well as muscle recovery after the effort.

Take a recovery supplement

Our recommendation is SportSeries Evorecovery, a supplement formulated to optimise recovery after training/competition.

Exclusive ALL IN ONE formula to take after physical exercise including

  • Complex Carbohydrates (Cluster Dextrin®, Palatinosa™, dextrose and fructose);
  • Hydrolysed protein (Lacprodan® Hydro.90 INS);
  • Essential aminoacids (obtained from vegetable fermentation);
  • Minerals (Calcium, Chloride, Magnesium, Potassium, Sodium);
  • Additionally it is Vegetarian and Gluten-Free.

What do I take?

In long cycling workouts (from 90 minutes and up), several continuous spinning classes, as well as the days before triathlon, I always carry a bottle with isotonic drink.

The one I’m taking is Evodrink 2.0 from SportSeries, orange flavour. Here the important thing is to know the relationship of isotonic product to the amount of water.

For a 750 millilitre bottle, add two parts isotonic mix, so that you achieve a balance.


  • For the beverage to be considered isotonic, it must have a ratio of 8 grams of glucose per 100 ml of water.
  • With two large tablespoons, about 50 grams, for a 750-800 ml bottle, I think it’s fine.

Another supplement I am taking before, during and after the most intense training is electrolytes powder also of the same brand.

It also dissolves in a bottle of water.

We must bear in mind that drinking water alone does not guarantee rapid water replacement and a lot of urine flow will occur, a situation that can be alleviated by the inclusion of electrolytes to ensure a preservation of the plasma volume in both effort and post-effort.

Substances that we must replenish during exercise

In sports endurance sports, such as a half marathon, electrolytes are lost by sweat and it is necessary to replenish them through supplements and/or liquids containing electrolytes.

Know that water contains electrolytes, but in very low proportions.


It will therefore be important to include isotonic drinks to replenish the previous days in optimal quantities.

Electrolytes are mineral salts (sodium, potassium, bicarbonate, calcium, magnesium) that are present in our body: In the blood and other bodily fluids.

Related Entries

  • We tell you how to optimise performance in a Half Marathon in this link.
  • Do you know the Science-endorsed Running Supplements? Discover them, click here.
Review of Half Marathon Diet

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What to eat during - 100%

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About Isabel del Barrio
Isabel del Barrio
Isabel del Barrio really loves sport, demonstrating it from a very young age and sharing her enthusiasm and knowledge to this day
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