August 15, 2020

Macronutrient Split for Endurance Athletes

When you're thinking about how to fuel your body to be able to match your training load, the first thing you typically do is to get an estimate of the energy you're about to spend. Depending on your training goals, this gives you a pretty good idea about how much you should eat. Basically, it's a simple "Energy in - Energy out" equation:

To keep your body in an energy balance, you need to feed it as much energy as you're going to spend throughout the day.

While this is a very good start, it's not quite that easy. Why? Because not all "energy" is the same.

While it's true that 100g of fat and 225g of carbs have the same "energy" (900 kcal), your body doesn't use it in the same way. And depending what you want achieve, one source is better suited for your goals than the other.

You probably noticed this already when you took an energy gel or ate a bar during a workout: These products typically consist mostly of carbohydrates and contain little fat, because during intensive physical activity, your body needs carbohydrates more than other energy sources.

Fuelling your body in an optimal way is not only about keeping an energy balance, but also using a mix of different energy sources that match the challenges your body has to face on a daily basis.

What are macronutrients?

Those different sources of energy are called "macronutrients", and you know them well:

Carbohydrate, Protein, and Fat.

Carbohydrates are things like bread, pasta, rice, quinoa, vegetables and fruits and such. Protein is commonly found in eggs whites, meat, fish, but also non-animal sources like lentils, tofu or saitan. And good examples for fats are oils or butter, but other kinds of food have a high fat content, too: For example nuts or egg yolks.

Of course, this is a simplification, and it actually is a bit more complicated than that - most natural foods consist of all three macro-nutrients, but usually, one is particularly dominant.

These three basic energy sources have very different functions for our body:

Carbohydrate is mainly the fuel for our muscles. It is also vital for our cognitive functions. Protein can be used as an energy source (if carbs are depleted), but is mainly needed for repairing old tissue and creating new tissue. The body uses it to repair muscle damage and create new muscle. And fat is both a basic building block of the body, and possible fuel for low-intensity activity. 1

Wether you're working out or not - your body needs all three kinds of energy: Carbs as fuel for your muscles, protein for protecting and building tissues, and fat for vital functions of your body.

So, it's important to not only look at how much food you're eating, but also which energy sources - macro nutrients - it contains.

This consideration of how much energy should come from carbohydrates, protein or fat and the resulting mix of energy sources is called "Macro Split". It tells you how your daily energy intake should look like to effectively fuel your body and make sure it's properly fuelled for the strain ahead.

Considerations for a suitable Macro-Split for Endurance Athletes

How does an ideal macro-split for endurance athletes look like? Since your daily intake is fixed and determined by both your training and your everday life, the three energy sources are basically competing against each other: Taking in more protein reduces the amount of fat and carbs you can eat, and the other way round as well, of course.

The main purpose of finding a good macro-split is to maximise intake of all three energy sources (up to the point where you would be consuming more than your body could use).


As an endurance athlete, getting in enough carbohydrates should be your primary concern.

"There is some historical evidence that our human ancestors consumed very little carbohydrate and survived. However, when considering athletes and the mountain of research demonstrating that carbohydrate is clearly the limiting substrate in athletic performance , it becomes clear that human survival and human performance are entirely different matters." 2

Carbohydrates are the main and essential fuel source for your muscles. Although your body can burn protein and fat if in a pinch, it always prefers to burn carbohydrates because it allows your muscles to work on a high performance level.

How much carbohydrates you need depends both on the volume and on the intensity of your training. As a rule of thumb, a bit more than half of your energy intake should come from carbohydrates.


Protein can perform two main functions for your body: First, it can be used as fuel. But this is not very efficient, and generally not desired. And second, it is used to repair existing and build new tissue.

If enough carbohydrates are provided, protein will not be used as fuel and can be used for other, more important functions.

Assuming that fuel for your muscles comes primarily from carbohydrates, you only have to eat enough protein to make sure your body can repair any muscle damage incurred by your training, and build new muscle if needed.

Recommendations for protein intake vary and a common recommendation is 1.2 to 1.7 gram protein per kg bodyweight. Depending on your personal situation, this translates to around 12% to 18% of your total daily intake.


Fat is the least important energy source for endurance athletes. When designing a macro-split for endurance performance, it's more about limiting the fat intake and make sure that enough caloric intake is available for carbs and protein.

Recommended Macro-Split for Endurance Athletes

The trick now is to create a macro-split for endurance athletes that is also compatible with "everday life", works with food that is regularily available, and is sustainable over a long period of time.

For most athletes, such a split will roughly look like this:

55% carbohydrates, 15% protein and 30% fat.5

This split works well for serious endurance athletes who perform on an amateur or hobby level. Athletes from higher performance levels may want to reduce the fat content and increase the carbohydrate share.

Considering two predominant ideas that are out there ("protein is most important" and "fat is bad"), this might look counter-intuitive, but this macro split has been found to be both beneficial for most athletic goals and sustainable.

Applying this macrosplit to food

How does that macro-split look like in practice?

Consider an athlete with a daily energy intake of 2.000 kcal. Splitting this intake into the three energy sources and applying this macrosplit, we arrive at the following values:

Carbohydrates1.100 kcal275 g
Protein300 kcal75 g
Fat600 kcal66 g

Note that we are talking about the "pure substrate" here. Most energy sources do not provide 100% substrate, but significantly less (100g pasta does not contain 100g carbohydrate).

How does this macro-split look like with "real food"?

The fat component might look big, but remember that fat is very energy-dense, and 600kcal translates to roughly 5 table spoons of olive oil.

75g of protein can be found in three cans of tuna, one and a half chicken breast, or 500g of tofu.

And 1.100 kcals of carbs (275g) would mean you have to eat 360g of brown rice.

As you can see, this macro split is actually quite reasonable, even if it looks very carb and fat heavy.

Macro-Split and Nutrfy

When Nutrfy is matching a meal to your individual daily plan, it will always try to stick to the macrosplit as defined above. Only when the total energy delivered deviates wildly from what you need it will switch over to a more energy-compliant version of the meal.

How well this works is dependend on the recipe you are using.

Custom Macro-Splits

You can define your own, individual macro-split if you have very specific needs. You can change it under your Athlete Profile - Advanced.


Considering your macro-split is very important when tailoring your food intake to your training. As endurance athlete, carbohydrates are your main source for energy, while protein and fat help your body to repair and maintain its functions.

Nutrfy helps you with that by automatically adjusting all your meals to your ideal macrosplit, making sure that you get all the macro nutrients you need to perform at your optimal level.

  1. Benardot, Dan. Advanced Sports Nutrition. Human Kinetics, Inc.

  2. Benardot, Dan. Advanced Sports Nutrition. Human Kinetics, Inc.

  3. Schek, Alexandra (2013). Ernährung im Top-Sport. UZV. Pages 58, 66, 77.

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