How to optimize triathlon performance by nutrition.

May 14, 2019 12:30:30 PM
10 min read

How to optimize triathlon performance by nutrition

As we all know, Triathlon consists of three disciplines: swimming, cycling and running. Or does it? Actually, experienced triathletes will tell you there is a fourth discipline, requiring just as much attention as the other three for optimal performance, and that is triathlon nutrition.

The impact of nutrition on performance is so great that Luc Van Lierde – double Ironman World Champion – has even referred to it as ‘the single most important factor on race day’.

Important, but confusing. Nutrition can be daunting to novice and experienced triathletes alike, due to the large amount of different opinions and mixed marketing messages you are confronted with. So let’s cut through the confusion and have a look into the basics of sports nutrition for triathletes.

Triathlon nutrition: basic definitions

To start with, let’s look at a few basic definitions we will use throughout this page.

‘Macronutrients’, or main classes of food, are a way to categorize the main nutrients in our diets. They are:

  • Carbohydrates
  • Proteins
  • Fats
  • Water

Let's have a closer look at each macronutrient in more detail.

Carbohydrates in triathlon nutrition

carbohydrates for triathlon

Carbohydrates are of huge importance to an athlete. They are the body’s preferred source of energy, which also defines carbohydrate’s main purpose: to provide the body with fuel.

Carbohydrates are essentially sugars or starches that the body breaks down into glucose, a simple sugar that the body can use to fuel its cells. They are often classified as ‘simple’ or ‘complex’, depending on how long their chain is and how many molecules they contain.

  • Simple carbohydrates are often called ‘sugars’, and can be categorized as single sugars (monosaccharides), which include glucose, fructose and galactose, or double sugars (disaccharides), which include sucrose (table sugar), lactose ( found in milk) and maltose. They generally have a sweet taste and are digested very fast, raising blood sugar levels rapidly.
  • Complex carbohydrates, also known as polysaccharides, are starches formed by longer saccharide chains, which means they take longer to break down. Chemically, they usually comprise of three or more linked sugars. Examples are white bread and pasta, but also maltodextrin, a corn starch consisting of long chains of glucose.

The healthiest complex carbohydrates are the least processed ones, with a slow digestion rate e.g. vegetables, whole grains and legumes (such as lentils, chickpeas and soy beans).

Indigestible carbohydrates are fibers. They  have an important role in regulating gut health.

All carbohydrates deliver 4 kCal of energy per gram.

Diet guideline: as a triathlete, you should aim to consume between 5 and 11 grams of carbohydrates per kilo of lean body weight per day, when training 1 to 5 hours per day.

Protein in triathlon nutrition

protein or triathletes

Protein, the second macronutrient, can be considered as providing the building blocks of the human body. They do most of the work in cells and are required for the structure, function and regulation of the body’s tissues and organs. For athletes notably they build muscle and bones.

Proteins are made up of 100.000’s of smaller units called ‘amino acids’, substances that all have their own role in the human body and athletic performance. The ratio and presence of these amino acids determine the quality of the protein for human consumption.

9 amino acids are considered to be essential.

In other words: the body cannot make them by itself, they need to be supplied by the diet. These amino acids are:

  • Lysine
  • Leucine
  • Isoleucine
  • Tryptophan
  • Phenylalanine
  • Threonine
  • Valine
  • Histidine
  • Methionine

Tip: Pay special attention to leucine in triathlon nutrition!

This amino acid is essential for muscle building and repair. The high leucine content of whey protein makes whey so efficient at building muscle. That is also the reason why plant-based proteins tend to produce less muscle synthesis, unless you have a plant-based protein with added leucine.

You can read more on leucine and other amino acids in triathlon nutrition in this article.

Just like carbohydrates, protein contains 4 kCal per gram.

Diet guideline: as a triathlete, you should consume between 1,2 and 2 grams of protein per kilo body weight:

  • if you train <1 hour, target 1.2 grams/kg/day
  • If you train 1-2 hours, target 1.2-1.4 grams/kg/day
  • If you train 2-4 hours, target 1.4-1.7 grams/kg/day
  • If you train 4+ hours, target 1.7-2.0 grams/kg/day

 More about protein in triathlon nutrition in this blog article.

Fats in triathlon nutrition

fats in triathlon nutrition

The third nutrient we find in our food is fat. Do you think it has a bad reputation? That’s right, it has.  But fat is actually essential to our body – the right type that is. Fat delivers energy (especially in the lower heart rate zone), absorbs nutrients such as vitamins and maintains your core body temperature. Without fats, you cannot survive. That is why the body is so efficient at turning excess calories into fat, it’s its favorite energy storage.

There are 4 types of fat:

  • Saturated fat

is a type of fat in which the fatty acid chains have all or predominantly single bonds. You find it mostly in animal food sources (such as meat ), they are often linked to heart disease and heightened cholesterol. A saturated fat tends to be solid at room temperature.

  • Monounsaturated fats

You find them in olive oil, avocados and many nuts and seeds. This is a healthier option since they contain a double bond in their chemical structure. These fats are beneficial for your health and have been linked to good heart health, for example within the Mediterranean diet.

  • Polyunsaturated fats

are the healthiest version available. They are essential fats. This means that they are required for normal body functions but your body can't produce them. So you must get them from food. Polyunsaturated fats are used to build cell membranes and to cover nerves. They are needed for blood clotting, muscle movement and fighting inflammation.

AdobeStock_179580841Well-known types of polyunsaturated fats are the Omega 3 and Omega 6 versions, linked to healthy hearts, eyes and brains.The amount of research on the health benefits of Omega 3 is staggering. It is a must in any diet, especially an athlete’s. You find Omega 3 in fatty fish such as salmon, mackerel and sardines but also in flax seeds, walnuts, etc.

  • Transfats

The worst type of fat possible, these man-made fats are actually a by-product of hydrogenation, used to turn liquid fats into solids to prevent them from becoming rancid. Strongly linked to inflammation, cancer and heart disease, they are typically found in margarines and highly processed foods such as fast food. You should avoid them at all cost.

Fat contains more than double the energy of carbs or protein, at 9 calories per gram.

Water in triathlon nutrition

water in triathlon nutrition

Although it does not contain calories, water should really be considered the most important nutrient on the list. Are you surprised? Without a shadow of a doubt, it is the number 1. Especially for triathletes! Without water you will dehydrate and die in a matter of days.

Some jaw-dropping facts & figures on water

  • Your brain is 75% water.
  • Bones are 22% water.
  • Muscles are 75% water.
  • Your blood is 92% water.


  • carries nutrients and oxygen to all cells.
  • is required for breathing.
  • moistens oxygen for breathing.
  • regulates your body temperature.
  • protects and cushions vital organs.
  • cushions  your joints.
  • helps to convert food into energy.
  • helps your body absorb nutrients.
  • removes waste.

For an athlete, it is extremely important to stay hydrated to support performance. For this purpose, Isotonic drinks have been developed to ensure proper hydration during longer training sessions.

Read more about isotonic drinks in this blogpost.

Why nutrition is so important for triathlon performance

Now we have refreshed the basics, it’s time to dive into the action: triathlon training.

As a triathlete, you have long training sessions, several times a week, with a high sweat rate and often high heart rates. Right? :-) Racing can be even more extreme. Many athletes show a tendency to have races in summertime and/or in hot locations, demanding even more of the body.

All this put a special strain on your triathlete’s body. So special attention needs to be given to these 3 aspects:

  • Stay hydrated
  • Keep fueling your body
  • Recover fully

Let's go into a bit more detail!

Stay hydrated

Before anything else, keep this in mind. Staying hydrated is probably the most important action you can take as a triathlete. Neglecting to do so will set you up for failure – or worse.

  • Per 1% of weight loss, your heart rate increases 3-5 beats per minute.
  • Dehydrate more than 2% and your performance WILL suffer.
  • More than 3% dehydration puts you at medical risks such as heat stroke, faintness, gastrointestinal problems, even cardiac arrest.

But beware. For a triathlete, drinking only water is not enough to prevent this. Sometimes it can be even more dangerous than not drinking at all.

The body sweats out minerals called ‘electrolytes’ that are essential to its functioning, sodium (as found in salt) being the most important electrolyte. Drinking only water during a prolonged effort such as training can flush too much salt out of your body, a condition called hyponatremia. This condition can cause faintness, dizziness but also more serious conditions such as heart arrhythmia and coma.

Salt also combines with glucose to efficiently transport water across the intestinal barrier into the bloodstream. When 2 sodium molecules combine with 1 glucose molecule to pass the intestinal barrier, they drag along 260 water molecules into the blood!  So you can see that optimal hydration is achieved by combining water with the right amount of electrolytes and glucose, as found in our Isotonic.

sodium glucose-2

What to drink, how much and when during triathlon training?

FREE download! Get an in-depth look into this fascinating topic and discover all practical guidelines of triathlon nutrition experts in our e-book on hydration here.

Download eBook


Keep fueling your body

As we saw in the definition above, glucose is the body’s favorite source of energy. This is even more so during intense training.  The more intense an effort is, the less fat the body uses to fuel this effort, and the more it relies on glucose.

glucose vs fat

However, glucose is stored in limited amounts as glycogen in the body, meaning you ‘run on empty’ after a few hours of intense efforts – like a race. Novice marathon runners refer this as ‘bonking’ or ‘hitting the wall’, and it usually occurs after 2-3 hours of running.

The key is to keep fueling your body with sugars during the training or race to avoid depleting your glycogen.

FREE Download!  Discover how many carbohydrates you need during racing in this free ebook on racing nutrition.

Download our eBook

A very important aspect in fueling without causing gastrointestinal discomfort, cramps or even diarrhea is to distribute the total intake of carbs over 2 sources in a 2:1 ratio. This ensures that no undigested carbohydrates remain in your intestines, causing the well-known issues.

Read more on the importance of this ratio in this blogpost.

Do you prefer 100% personalized advice?

No problem, we have developed  a Nutrition Planner to calculate exactly what you need, when and how much! Check out it's features on this short video: 

Hiddit nutrition planner walkthrough


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Check out the planner

Recover fully

triathlete recovering

A frequently made mistake by triathletes? They make the mistake of overtraining, neglecting the fact that your body needs to rest to adapt and become stronger – hence making progress.

Nutrition is an invaluable part of recovery, as your body will need building stones to repair muscle damage and carbohydrates to replace depleted glycogen. That is why you need to provide your body with high quality protein and carbohydrates, preferably immediately following your training or race.

  • the protein will be used to repair muscle damage and increase the muscular endurance;
  • the glucose will be stored as glycogen and assist in shuttling nutrients to the muscles.

Science has demonstrated that combining carbohydrates and protein in a post-workout meal will result in better recovery, especially when taken within 45 minutes after completing the training.

Attention also needs to be given to rehydration. You should aim to drink 1.5 times the fluids lost during the hours following your training or race.

Triathlon nutrition: a common sense approach


Does sports nutrition mean that you have to live of gels and sports drinks?

The answer is definitely: no, you don’t.

The base of performance – and health – lies in a balanced approach to diet. There really are no shortcuts to success and no pill can make up for poor diet habits.

Some sound dietary advice

  • Focus on eating high-quality carbohydrates and protein from unprocessed sources. This will also make sure you eat only the healthy fats. 
  • Try eating 20 grams of protein 4-6 times a day, depending on your training load. Use a high quality protein shake when you don’t have time for a real meal (or at breakfast).
  • Focus on plenty of unrefined carbs such as quinoa, brown rice,… and vegetables, avoiding to eat too much sugar. Switch to simple carbs (such as white bread, honey,…) and sports nutrition such as Isotonics and gels during training to ensure fast digestion and minimize stomach trouble.
  • Keep an eye on your hydration status. Simple trick: monitor your urine color and your bodyweight.
  • Make sure to get a Recovery shake or a combination of carbs and protein after your workout.
  • Load up on carbs the day before a race.
  • Use selected supplements if you have a vitamin deficiency or are looking for a specific effect (such as the fat-burning effect of L-Carnitine, or the antioxidant benefits of Ubiquinol).

Your nutrition does not need to be rocket science, just paying a bit of attention to sound eating habits will bring you a lot closer to reaching your full potential.

Stay tuned for more tips and tricks on our blog!

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