Macros for Endurance

Blog post by Ph Nutrition

I think I speak for most people when I say that the past year has been dreadful for most people’s strength goals! The lack of access to sufficient load and the lack of consistency across the year has definitely affected me in that department. But when one door closes another opens and with the lack of opportunity to improve on strength came the fantastic opportunity to work on endurance. So I, like many others, laced up my running shoes and started incorporating more and more endurance training into my life. As with everything in nutrition I wanted to make sure that the goals from my training were matched by my nutrition and so made some key changes to my diet to maximise the adaptations I was aiming for. Here we’re going to dive into exactly that!

We will look at the physiological determinants of success in endurance training and how training brings about improvements in these factors before then diving into how to manipulate your macros to marry the training. We’ll look at being as efficient as you can with your macros and fuelling the work required. 

First things first, when looking to improve your endurance performance what is it that you’re actually looking to change?! Looking from the top down, the things we’re striving for are essentially the ability to delay the onset of fatigue at varying exercise intensities. To be able to go for longer at lower intensities and for the baseline intensity to be higher across the board right?! We want to be moving faster for longer. Over the years there have been several papers looking at the determinants of endurance performance and they all essentially come back to 3 factors! Your aerobic performance (measured by your Vo2 Max and lactate threshold), your anaerobic performance (measured by time spent above the lactate threshold) and your mechanical efficiency which can manifest itself as running economy or cycling economy.

Here’s a fantastic flow chart taken from Joyner and Coyle’s (2008) “Endurance Exercise Performance: The Physiology of Champions”  showing how those 3 factors are linked to overall performance and the underlying physiology of our bodies. 

As we can see from this, the line of determinants at the bottom are the things that we can influence (well some of them) in our physiology through training and nutrition to improve our overall performance. Endurance training itself is found to improve these on its own but nutrition can be manipulated to amplify those adaptations even more. 

Before we dive into specific macronutrients and make changes to those. It’s first important to touch upon that all important aspect of energy balance. Because yes, it still matters. Being in a caloric surplus or deficit will affect some of these physiological markers, the most common example in endurance work is perhaps being in a controlled caloric deficit to reduce fat mass to improve mechanical efficiency. This is of course useful for improving performance, but being in a prolonged caloric deficit around competition is NOT going to improve performance as energy availability will be low. It’ll be important to periodise when you carry out these  changes, something we will touch upon later on. 

For now though I believe it’s worth highlighting the energy cost of endurance training, as it is often underestimated. In 2017, Heydenreich et al carried out a systematic review looking at energy expenditure, intake and body composition of endurance athletes across their training season. The results for energy intake and expenditure are shown below.

We can clearly see that energy expenditure is dramatically more around certain times of the year, again we’ll touch on this later. But we can also see that for the most part, energy expenditure seems to be more than energy intake for both males and females across the training season. Obviously this is not going to be the case for everyone as those with proper nutrition planning will counter this, I believe it’s just worth noting the larger energy cost of exercise as it’s often underestimated and can thus lead to symptoms of RED-S. (See article on RED-S, there has to be one on the hub right?!)

Ok, so we’re aware of the energy need for endurance sports. Now to look at where we should get this energy from to be efficient with our nutrition and bring about the physiological changes we want. Let’s start with everyone’s favourite macronutrient as it’s perhaps one of the simplest to deal with from an endurance point of view. I am of course meaning PROTEIN. Here we want to think about mechanical efficiency, we don’t necessarily want to be increasing muscle mass, more just improving the strength and endurance of the muscle we have. SO do we need to eat as if we were stimulating hypertrophy? Probably not. Let’s use me as an example here.

Above we have two pictures of me. On the left I am sitting at 75kgs and my goals with training are to increase muscle mass and strength. I was consuming around 2g of protein per kg body weight per day and spacing it out across my day in servings of around 30g of protein per meal. These are common recommendations for maximal muscle protein synthesis and they seemed to work for me (who knew ay). There is some emerging evidence on more (potentially up to 4g/kg BW per day) being beneficial but for me, this target worked.

On the right, I am running the Sheffield half marathon and weigh 5kgs less. I’m short and stocky, built like a hobbit on creatine, i.e. not for running. But I still wanted to tailor my nutrition to suit my goals. I knew that I had to alter my mechanical efficiency and maximise my efficiency of fuel usage! SO protein took a hit, I took it down to around 1.6g per kg body weight to maintain some of the muscle mass I had but to also make room for more carbohydrates and fats. I was not looking to build muscle, just maintain what I had and could even potentially have gone lower! 

Recommendations of around 1.2-1.6g per kg BW for endurance training have been thrown out! But as with everything it’s relatively fluid and can change dependent on the more individualised goals and needs of the athlete. It’s also worth noting that if you are planning a fat loss phase to improve mechanical efficiency then more protein might not be a bad thing! This is why the fluidity of targets is key, they should match your goals at that point in time.

Sweet, protein sorted let’s move on to carbs and fats. We’ve lumped these together as the manipulation of them will be KEY in bringing about the physiological changes we want such as aerobic enzyme activity. 

In recent years there has been an incredible surge in the amount of research going into ketogenic diets and endurance performance. One of the driving theories behind this research is that we can essentially store more energy in the form of fat than we can in the form of carbohydrates. Our body can store around 600g of glycogen, this equates to about 2400kcals worth of energy. Fat stores on the other hand are larger, and fat itself packs more of an energy punch. Let’s use some maths for context, imagine a lean 70kg man with 10% body fat, they have 7kgs of fat on their body! Obviously some of this is essential for our bodies to survive, but for the sake of this, let’s say it isn’t. 7kgs of fat is around 63000kcals. Thinking back to our energy expenditure table, this is enough to fuel multiple days of training even in the competition phase. 

So if we can access these stores of fuel surely fat is going to be our best source of energy for endurance work?! Let’s look at this from perhaps the most extreme example of “fat adaptation”, the ketogenic diet. There are many supporters of the ketogenic diet in both the general population and the academic world, the notorious Tim Noakes is just one of these. Because of this support and the potential benefits of accessing our fat stores to fuel us, there has been a large amount of research into the ketogenic diet and endurance performance. In 2019, Dr Fionn McSwiney wrote a review article on just this. (  

He found that ultimately the ketogenic diet offered no significant advantage to athletes across any kind of intensity or time domain. Most studies showed that although there was no decrement in performance for low to moderate intensities, there was also no benefit from going keto. However at the top end of the intensity scale it seems that decreased power output and thus performance occurs when people have followed the ketogenic diet. This makes sense as at those high intensities anaerobic metabolism dominates, of which glucose and glycogen are our bodies preferred fuel source. So it seems that going keto offers no benefit for performance and can even lead to you losing that 5th gear! Carbs are most definitely still kind for the most part.

Although the ketogenic diet offers no discernible benefit and carbs are still king for competition performance, there may be a way that we can use fats to our advantage. If we can increase our bodies metabolic flexibility so that it uses fats at low intensities when plenty of oxygen is present and then spare our carbohydrate stores for when we really need them then this may improve our capacity. This is an idea that has been taken into practice via the Train Low Compete High principle. 

The train low compete high principle is exactly what it says on the tin! Carry out some periods/sessions of endurance training in a state of low glycogen availability but compete in a state where carb stores and energy availability is HIGH! In this way metabolic flexibility can be achieved and the benefits of carbs still used. Personally, I don’t believe that training low across the entirety of the training year or season is a good idea. I believe that it should be periodised both week to week and across the season. Let’s put this into context using another graph from Heydenreich et als 2017 paper on endurance athletes energy expenditure. 

This graph lays out the changes in intensity and volume in an athletes training across the season.

As you can see in the competition phases, intensity is higher than in early preparation. To me this says early preparation phases are a fantastic time to incorporate some training low into your routine. The intensity won’t be high and so in terms of dominant fuel sources, you won’t be as dependent on glycogen and carbs. You can lay the groundwork for metabolic flexibility and carb sparing in the early stages before increasing carbs as intensity increases across the season.

You can also look to periodise like this within the week with some micro periodisation. This would essentially look like adaptive and performance sessions. I.e some sessions whereby you train low and work to improve fat oxidation but the performance of the session may suffer (adaptive) vs other sessions in the week that you go in well fuelled for, ready to perform! Not every session will need to be adaptive and if every session is a performance session you’re bound to miss out on adaptation.

Having established that training low and periodising your macros around this can improve your endurance performance, here’s an awesome diagram taken from a blog by Coach Patricia on training low! 

On that blog Patricia dives into the physiology behind training low, what adaptations it brings about and how to do it that suits you and your training best. Here’s the link to that blog, it is well worth a read if you’re considering training low.

Anyway, back to the big picture of macros for endurance training. We’ve covered protein carbs and fats but now let’s put them all together! We’ll use myself as an example for context and to get some numbers down, but before that we want to attack a framework for periodising your nutrition. This is a framework laid out by Trent Stellingwerff et al in a 2019 paper and it follows a flowchart of decisions based all around the determinants of success!

Let’s put this framework into practice using what we know about macros for endurance and limiting factors. We’ll use myself as an example! I am 5ft7, and weigh around 75kgs, I’m built like a hobbit on creatine and not a natural born runner. Let’s say I want to run a marathon, I set a date in let’s say 3 months and get training. Initially because of my frame one major gap for me will be mechanical efficiency, so i’ll plot out a phase that involves some fat loss to ensure I lean out a little and mechanical efficiency can improve! This will be in the early stages of my training so intensity will still be relatively low. I’ll be in a caloric deficit (which for me is anything less than 3000kcals at the minute based on an RMR test) and i’ll attack some low and slow work so my carb intake may be reduced, i’ll keep my protein intake relatively high to encourage fat loss as opposed to loss of lean mass. My macros would look a little something like this: 

  • Energy, 2500kcals/day 
  • Protein, 150g/day (2g/kg BW)
  • Carbs, 250g/day (around 40% of total energy contribution) 
  • Fats, 100g/day

I’d also periodise my carbs depending on the type of session I would be attacking. I’d incorporate fasted training in to this early stage and most sessions would be lower intensity. After around 4 weeks of leaning out, my mechanical efficiency would (theoretically) have changed. It would be time to head back to the flow chart and attack a new determinant of success!

In the early training phase I’d still be working to improve aerobic power, metabolic flexibility and just generally building my base! I’d take my intake up to maintenance and keep protein still relatively high in this early phase still, I would then essentially just bring carbs and fats up in the same proportion to keep the ratio the same.

Then as intensity and volume of training started to increase, I’d enter the comp phase! I’d want energy availability to be high SO protein intake would reduce to around 1.2-1.6g/kg BW, (the higher limit for me as I’m habitually used to getting so much in) carbs would then increase to fuel this high intensity training and get me ready for the insane amount of carbs i’ll be eating before and during an event! Fat would take a little hit and my macros might start to look a little like this.

  • Energy, 2800kcals 
  • Protein, 120g/day 
  • Carbs, 400g/day 
  • Fats, 80g/day

As you can see this is a fairly carb dominated diet and it’s important to note the context for this would be around the competition phase of preparation for an endurance event, not for daily life!

So there we have it, a deep dive into macronutrients for endurance training. We’ve covered the what, the why and the when around protein carbs and fats and endurance. It’s been one hell of a ride but it’s important to note that this is ultimately just the starting point! When it comes to nutrition and endurance there is still more you can attack, things like hydration, key micronutrients, what to do in comp week, carb loading and so much more.

I’ll be diving deeper into these over the coming months but for now, sink your teeth into some serious endurance work and depending on where your training’s at some carbs and fats!

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Written by Luke Hall – pH Nutrition