The Thinking Runner

HFLC Diet for Endurance Runners and Triathletes


Massive improvements – What is the context:

Many runners, inspired by Tim Noakes and stories of runners making massive improvements in their performances, are moving to the so-called ‘High Fat Low Carb’ (HFLC), diet.

There are some challenges, and in my opinion, mis-interpretations, with the HFLC diet as it is being promoted in the popular media.

One of the initial misperceptions is that because Prof. Noakes is driving this direction, the diet is for sportspeople.
The Real Meal Revolution is not a Sports Nutrition book: It’s a book for the whole population. Of course by definition it is impossible to cover the detailed consideration of all the variables in a massive population, so there will always be differences.

Prof. Noakes is himself a ‘special’ case as a pre-diabetic he has restricted his carbohydrate to minimal levels.
If one considers that licensed club runners in South Africa only account for 0.15% of the population and Comrades Marathon (90km race) runners account for 0.036%, then it is not surprising that their requirements may differ from the remaining 99%. The important message of the book and the diet lies in the principles, and background physiology.

Even the use of the word ‘diet’ is open to definition as this should be more a lifestyle than a diet, and the name HFLC can be misleading if left without context.

The purpose of this article is to put some perspective around the HFLC option and to provide some base from which each runner, and endurance athlete, can evaluate the information with a view to gaining something beneficial in life and running.

How High Fat is the HFLC?

It would be just as easy to ask how low carb is the HFLC lifestyle?
Just think about the difference in the questions for a minute and you will quickly appreciate that in today’s thinking the High Fat option is a more sensational headline. That effectively is why the name has been chosen.

Journalists listening to the information were attracted to the drive to increase fats, simply because we have been brainwashed for three decades to believe fats are bad: A total myth!

Why would some fats (omega 3 etc) be called ‘essential fats’ if fats were bad? And this is just a simple example, which links into the hormone cascade, without which we experience major problems particularly as runners hoping to recover from training.

Is it truly ‘high fat’?
Consider a typical workday where we squeeze in a 2-hour long run:

Lets take a layman’s (simplified) approach to analyzing the energy used and sources.

The run may burn 700 calories, and depending on the pace and person it can split at roughly 48% from Carbs and 52% from fats. You may call that ‘balanced’, but if you convert this into grams then the 366 calories of fat becomes 41 grams of Fat. The 334 calories of Carbs equates to 84 grams of carbohydrate.

So in comparing grams it is clear that this particular running is High Carb and Low Fat…. At least if evaluated in grams. By calorie comparison however it is ‘balanced’.
Clearly care must be taken in the context and expression being used.

Furthermore the faster the run the higher the carb consumption will be. Interval sessions, (particularly 400m and below), will be substantially higher carb, with the fat use coming primarily from the warm up and cool down.

Now consider the remainder of the day.
My personal analysis using 48 hours of recording of heart rate and variations on a Body Guard 2 with First Beat analysis, indicated that in a full day, (without the exercise) I then used 333 calories of carbs in the remainder of the day sitting at desks, walking to and from meetings and so on. That’s another 84 grams of carbs.

However I also used 930 calories from fat in this period, which works out at 103 grams of fat.
This means, (ignoring any calories from protein), in work and leisure time 74% of the calories come from fats, leaving 26% from carbs. No question this is High Fat.

In this context my use if clearly ‘high(er) fat and low(er) carb’ be it considered in calories or in grams.

We need to adjust this for protein. A sedentary person may require only around 0.6 grams per kg body weight.
Over the day I would have say 42 grams of protein, which is around 168 calories.

The percentages now become 12% Protein, 65% fat and 23% carbs.

Remember this is what I am using, which is only a guide to what I need to replace.

So it’s clear that if I don’t exercise the primary energy usage comes from fat, and we use only a small amount of carbohydrate for energy.

This high fat use at rest is not surprising, as we already know that the faster we run (exercise) the more we use carbohydrate for energy.

If we run flat out for 3 minutes then we use virtually 100% carbohydrate, (if only comparing Carbs and fat mobilization).

If we run 12-hour comrades then by far the greater proportion of energy comes from mobilizing fat, converting it into carbohydrate (glycogen) and then into energy.

It stands reason then that low level intensity or virtually zero exercise of sitting at a desk is ‘powered’ by an even greater proportion of fat mobilization.

If we consider the non-training day in terms of grams the use is around 42 gram Protein, 103 gram Fat, 84 gram Carbohydrate.

This is the physical use side of the equation, and of course the brain requires a constant supply of blood sugar to operate and maintain the body, make decisions and undertake the thoughts and work we do sitting at the desk.

The brains requirement is about 125 grams (5 grams or 20 calories per hour) of carbs per day at rest, the majority of which at low intensity levels can be provided by the liver through the conversion of fat into carbohydrate.

Assuming even a conservative 80/20 split between fats and carbs the overall rest day is going to be around 42-gram protein, 148-gram fat, 97 gram Carbohydrate. In percentages this is 15% protein, 52% fat, 33% carbs on weight.

You will also note that total amount of carbohydrate is 97 grams and well matched to 50-100 gram that Tim Noakes is promoting for the average person per day.

I have shared with Tim a small book I bought in UK for 47pence (around R8.50 todays cost) in 1974 that used a 50-gram a day restriction on carbohydrate for weight loss and then an increase to maintain. So a good fit to the current revolution.

That book highlights that going below the 50 grams could be unhealthy and that the 50-gram is to lose weight, so maintenance would be higher than that.
(Many people will know that Tim has said that because he is pre-diabetic he restricts himself to 25 grams a day. That is a medical decision in relation to his diabetes so not the norm.)

Now add in training: What happens?

Now consider if a runner adds in a 2 hour long easy run, then the protein requirement increases to say 0.8gram per kg (more if a intense session) and from run calculations the usage increases to around 56 gram protein 189 gram fat and 238 gram Carbohydrate which results in 12% protein, 40% fat and 48% carbohydrate.

Now this is not as High Fat as the headlines tend to perceive, and much more the ‘balanced’ diet that we have all heard about since the beginning of time….

However turn this into calories: 224 from Protein, 1701 fat and 952 carbohydrate; or 8% protein 60% fat and 32% carbohydrate.

The confusion in the naming of the diet is clear, as is the need to be aware of how sports training will impact on the usage.

The type of training changes requirements:
Now as previously mentioned if the training session is more intense the amount of Carbohydrate will increase as more is used with faster running.

While the majority of club runners will only train once a day this value is rarely going to exceed 200 grams in a day, which is the maximum recommended by Tim in the Real Meal Revolution. (Page 30 The Real Meal Revolution)

Putting this into meaningful terms, 200grams equates to:
• 10 medium sized boiled potatoes
• 8 portions of Pizza
• 20 slices of fresh Pineapple
• 10 medium apples
• 6 Bananas

Of course no one is suggesting you would eat any one of these exclusively, but it gives an indication of the quantity at top end of the carbohydrate range for the hard training club athlete, particularly when including high intensity work.

Remember also that the research showing the replenishment of carbohydrate stores using a high carbohydrate intake immediately after training was not incorrect. Nor was the need to commence carbohydrates in the first 15 minutes after training stops.

On the other hand we know that the more the runner trains in the low intensity ‘fat burning’ long slow run zone, the more efficient the runner will become in converting fat into carbohydrate, and so the amount of carbohydrate that needs to be consumed will also drop.

A Comrades runner in peak distance / endurance training will cut the carbohydrates to below the usage level as a means of enhancing the fat burning systems.

The practical impact of these latter comments is that anyone training will probably find their acceptable carbohydrate level around 90-150 grams per day, depending on the session.

Part (25-50grams) of this carbohydrate allowance per day should be taken immediately after training and that this should be carbohydrate that is quickly absorbed (high GI). This will assist in the absorption of protein and other nutrients to speed recovery, which should also be taken after training.

However if initially you are attempting to lose weight this daily carbohydrate figure may be less until you get the goal weight, then be increased to achieve recovery and performance.

Triathletes, Multiday training and professionals:
If you are training multiple times in a day (triathlete or professional athlete) then the requirement may well be even higher. Not only will you want to have carbohydrate immediately after each session, but also you will have an overall larger use of energy that requires to be replaced to prevent total depletion of carbohydrate from consecutive days of training.

A carbohydrate requirement does not imply the use of fast food, sweets, or junk food. The carbohydrate consumption would still be based around low glycemic foods and include the fruits and vegetables that have always been seen as part of any nutritional recommendations.

There is still a place for quality supplements.
For instance many people can not eat immediately (or within the 15 minute window) of a training session so using a 25-50gram drink such as Replenish will not only assist with hydration, it kicks off the carbohydrate replacement and importantly the glucose-insulin reaction for absorption of proteins and nutrients required for tissue repair.

While muscle damage is minimal in low intensity work, the use of a High Energy drink (as opposed to Replenish) is appropriate after a high intensity session as it provides both an initial blast of carbohydrate and proteins, amino acids and even medium chain triglycerides that will speed recovery.

Another useful consideration, particularly in the initial period of coming to terms with this HFLC approach, is to augment with a anti-oxidant multi-vitamin supplement almost as an insurance policy to ensure you are getting the essential vitamins.

Fat Supplementation:
Also there is a benefit in making part of the fat consumption from Omega 3 supplementation.

As with vitamins and anti-oxidants, the ideal is to use real food for all requirements, but the reality is that the HCLF lifestyle will take time to implement. The use of salmon, avocado, olive oil and the like are better ways to get the Omega 3 requirements but supplementation is a good protective measure until the runners gets fully adapted to a new way of eating.


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