How nutrition can support your endurance sports performance!


One of my best friends ran her first marathon last Sunday. An amazing achievement! There is no way I am going to do that in any near future. For now, I will just stick to my own (much lower) level of exercise. Inspired by her I looked up the effects of nutrition on endurance sports performance. Keep on reading for my findings.

Endurance sports

A marathon is a pretty extreme example of endurance sports. One of the definitions out there is that you should practice more than 30 minutes of continues exercise to call it endurance sports. This could be running, cycling, swimming etc. The most important nutritional factors in endurance sports are carbohydrate depletion and dehydration.

What to eat the days before your (half) marathon or other endurance sports event

If you are practicing more extreme forms of endurance sports you are probably depleting almost all the carbohydrates stored in your body. Your muscles and liver store sugar in the form of glycogen. This is the fastest energy source your body has. If you deplete your glycogen storage you will suffer form fatigue. The days prior to your sports event you can increase the glycogen storage in your muscles. This is called glycogen supercompensation. Increasing your glycogen storage only makes sense if you are practicing endurance sports for over 90 minutes. The level of benefit from glycogen supercompensation is very personal; some people benefit more than others. A disadvantage of glycogen supercompensation could be that you put on weight as a result of water retention. For every gram of glycogen you store, you also store 3 grams of water.

The day of the event: Eating and drinking

Eating a carbohydrate rich meal 3 to 4 hours before the start of your endurance sports event can have a positive effect on your performance. Eating carbohydrates 30 to 60 minutes before the start can have negative effects. This includes sugar rich energy drinks. The sugars in these drinks make your blood sugar levels rise quickly. Those same blood sugar levels then decrease rapidly 15 to 30 minutes after you started exercising. That is of course not what you wanted to achieve.

Dehydration is another important cause of fatigue. The general rule is that you should not loose more than 2-3% of your body weight during a sports event. This loss in body weight mainly consists of fluids. It is relatively easy to track this yourself. Just weigh yourself directly before and after training and calculate the difference.
On the day of your marathon you should slowly start drinking water four hours before the start. If you don’t produce urine or it is yellow you should increase your fluid intake two hours before the start.


How you can support your sports performance during the race

During exercise you can take fast carbohydrates (sugars, preferably a combination of glucose and fructose) in the form of sport drinks or gels. Even if you endurance exercise lasts less than two hours taking sugars can support your performance. The funny thing is that you do not even have to swallow the sugars. A mouth rinse with a high sugar sports drink is just as effective as actually swallowing that sports drink. If your training lasts more than two hours your body will use the sugars as fuel. In this case it is essential to swallow the sugars. The most effective is taking 60 to 90 grams of sugars per hour of your training. Lower doses are also beneficial; this is just the optimal dose. Taking protein in combination with carbohydrate during exercise does not show any additional beneficial effects.

Of course hydration during the race is also very important. As mentioned before, you should not lose more than 2-3% of your body weight. The amount of fluids you have to drink to achieve that differs per person and is dependent on the circumstances (weather, intensity, etc.). If you exercise more than 90 minutes it is important to drink more than just water. Low doses of carbohydrates and natrium will help the fluid to be taken up and maintain your natrium balance.

What did Natasja do?

Since I am not practising a lot of endurance sports I asked my friend Natasja (the one who ran the marathon!) if she could share her experience:

Natasja_Eten_Drinken_Marathon_Nutrition“Since I’ve been running distances of half a marathon and longer, I’ve discovered and experience a few things. As I’m approaching a run, I increase my carbohydrate intake over my normal levels, in the case of the marathon, this meant pasta almost every evening of the last week. Moreover, I ensure that I arrive well hydrated at the start of a run. Since the marathon starting time was at 9:30AM, that meant hydrating well already the day before. During a run, I compensate fluid loss with water and isotonic sports drinks and I take gels and banana for some additional energy. A good tip with regards to nutrition is to not deviate from your normal habits too much. In the marathon morning, I had my regular oatmeal in the morning.”

Used articles

  1. Jeukendrup, A.E., Nutrition for endurance sports: marathon, triathlon, and road cycling. J Sports Sci, 2011. 29 Suppl 1: p. S91-9.
  2. Kenefick, R.W. and S.N. Cheuvront, Hydration for recreational sport and physical activity. Nutr Rev, 2012. 70 Suppl 2: p. S137-42.
  3. van Loon, L.J., Is there a need for protein ingestion during exercise? Sports Med, 2014. 44 Suppl 1: p. S105-11.


PS Blogs on nutrition during recovery from exercise and supplements to improve sports performance are coming!

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