Fat burning for athletes

Asker Jeukendrup’s point of view

We are obsessed with fat burning! Some of us want to burn fat to lose weight or look lean, some want to burn fat because it makes them faster. But what is the evidence that we should burn fat and that fat burning is good for us?

People want to burn fat for 3 main reasons.


1. Weight loss


2. Training effect


3. Health


1. Weight loss

The number 1 reason is probably losing weight. Weight gain after Christmas is usually a result of increased body fat and if you want to lose this fat you will need to burn it off.  Also, athletes who already have low body fat and want to get even leaner are often interested in fat burning for this


2. Training effect

Fat burning is also popular because we associate it with being well-trained.

It is true that trained athletes typically have a higher capacity to burn fat. Weeks or months of training have changed the muscle, and this now allows the athlete to burn fat at higher rates. But note that the athlete can ALSO burn more carbohydrate….

In an analogy with a car: the engine is now bigger and can use more fuel and thus go faster. At a moderate intensity (speed) this makes you less dependent on carbohydrate and thus you spare your glycogen (carbohydrate) stores and that should help your performance.

3. Health

Fat burning is also linked to improvements in general health. This is mostly based on observations that if your body becomes very poor at burning fat (usually because of inactivity and a poor diet), people also seem to develop various metabolic and other health problems. If you train your body to burn more fat again, some of the health benefits will also return.



Fat burning: let’s look at the evidence

So, if these are the 3 prime reasons of why we are interested in fat burning, let’s now look at the evidence.


a. In order to lose weight, we need to be in negative energy balance. In other words: you need to burn more calories than you ingest. If you burn more fat but you still eat too much, you will not lose weight. Of course, when you are in negative energy balance, you want to make sure that the weight you are losing is mostly fat and this is where fat burning becomes more important. So, the take home message here is: for weight loss negative energy balance is far more important than fat oxidation per se.


b. The second point was that trained athletes are better at burning fat. In general, this is true, but not always. What is true is that any person can improve their capacity to burn fat through training and thus become better at burning fat. However, there are large individual differences and the starting points of different people can be very different. We don’t (yet) understand all the factors that cause these differences, but it is very likely that they are largely genetically determined. In one study we found that some sedentary individuals were able to burn similar amounts of fat as a highly trained


c. Finally, the effects on health. These are also related to the increased capacity to burn fat, not to just burning a bit of fat. The amount of fat you can burn during exercise is really small. Typically, fat burning occurs between 0.3 and 0.5 g per minute during exercise (in extreme cases up to about 1 g per minute). This means that in order to burn 1kg of fat we need to exercise 33-56 hours!


But the benefits come from increasing the size of the engine, increasing the number of mitochondria, so that even in resting conditions you will be able to burn more fat. For someone who is not very active, eating less carbohydrate will further help, but the biggest effect will come from the beneficial effects of exercise.


The bottom line

The bottom line is you need to get out there and use your muscles, train them to become better at fat burning. Everyone can improve their fat burning, increase their exercise capacity and get healthier in the process.


Professor Asker Jeukendrup is one of the world’s leading sports nutritionists/ exercise physiologists who spent most of his career as a professor at the University of Birmingham (UK). Dr Jeukendrup authored 8 books and over 200 research papers and book chapters. His expertise stretches from exercise metabolism and sports nutrition to training and overtraining. He is currently a (visiting) professor at Loughborough University and director of his own performance consulting business “Mysportscience” and communicates science through the popular website mysportscience.com. Asker works as Performance Manager for the Dutch Olympic team and is Head performance Nutrition for the Lotto Jumbo Pro cycling team. He also works with FC Barcelona, and other elite football clubs. Asker practices what he preaches and completed 21 Ironman races including 6 time the Ironman world Championship in Hawaii.