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FatMax, What is it and how do you train it?

FatMax is the highest rate of fat oxidation. It is the maximum of energy (kcal) from fat combustion per hour of exercise. In endurance events a high FatMax is associated with high endurance performance.

While carbohydrate stores (glycogen) are limited, utilising fat as a fuel can help to spare carbohydrates.

Fat combustion is the bottleneck of endurance performance in sports like running and triathlon. You can create strategies to increase your energy expenditure from fat and thereby enhance your performance.


  • Fat combustion rates are highly individual metrics.

  • Accurately understanding fat combustion in is crucial in endurance sports.

  • Significant differences are observed both between different athletes, and between different states of training in the same athletes at different times.

  • Knowing the FatMax Zone allows you to train fat combustion most efficiently.

Below are some strategies you can use to train and improve FatMax



Let’s say you perform a high intense interval in training.

During this effort, lactate will accumulate. In the resting period between intervals the low intensity is usually where fat combustion would be high.

However, in the recovery phase between or after high intensity intervals,

fat combustion is low. Instead, the preferred fuel for muscles in this period

is the accumulated lactate.

The low intensity recovery periods are needed to combust lactate

and recover faster.

The same is true during training intended for “fat burning”. Any time

lactate is accumulating during the exercise, fat will be pushed out of the

aerobic metabolism. Until muscular lactate levels decrease again, fat

combustion will stay lower.

All of this means that it is of utmost importance to avoid short, high

intensity bouts which cause high lactate levels during training which is

meant to be in the Fat Max zone.



Low carbohydrate diets, and training in low carbohydrate state, have

become more and more popular in endurance sports.

This idea is based on findings that a state of low carbohydrate availability can increase


A lowered carbohydrate intake due to an altered diet can decrease the

capacity of carbohydrate metabolism.

In doing so, fat combustion will be elevated.

The result of this is not just an immediate elevation in the percentage of fat combustion, but also an increase in the capacity of the enzymes involved in fat combustion. This can lead to a prolonging of the higher capacity to combust fat. Bear in mind that after your athlete’s diet is back to a higher carbohydrate content, the effect previously described can easily be reversed. The activity of enzymes involved in the carbohydrate

metabolism will go back to a normal state.

During a period of lowered carbohydrate intake, it is crucial to minimise

high intensity workouts in which carbohydrate combustion is high. This is

because, during high such efforts, the body needs to use carbohydrates as



A higher VO2max = better aerobic metabolism= improved capacity to

burn fat.

A higher VO2max will lead to better fat combustion in your athlete. This is

because it creates more mitochondria, improved blood flow due to higher

capillary density, and a shift from high glycolytic muscle fibre types to

“endurance” types (slow twitch fibres). All of this means a better aerobic

metabolism, which then pushes back the involvement of the glycolytic

(anaerobic) metabolism.

This results in an improved ability to burn fat. As combusting fat requires

more oxygen for the same energy spend compared to combusting

carbohydrates, an increase in VO2max will always result in an improved

capacity for burning fat. This is true whether accomplished with many

hours of low intensity training, or with very hard interval workouts.


With the sleep low strategy is completed over an evening and the following morning i.e. Friday evening Saturday morning.

On Friday evening you complete a High Intensity Interval session. After the session you take in as little carbohydrate as possible post exercise. This delepetes your glycogen stores.

On Saturday morning you after sleeping low you perform an endurance session. Low intensity and fasted without breakfast.

This may be uncomfortable for the first couple of times you try it but after a while you will adapt and it becomes more manageable.

It can take a little more time to recover from these sessions so they should be planned carefully. You can periodise these sessions into your training.

The high intensity session the night before is an important part of this overall strategy. It is important that it is not skipped.

These are some strategies that you can incorporate into your training sessions.

If you would like to learn more about how you can determine your own unique individual FatMax click here

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