Everything you ever wanted to know about working out on an empty stomach.

Training auf nüchternen Magen

Harmful or beneficial?

Who hasn’t heard about training on an empty stomach? While some flatly deny its benefits, others truly believe in this strategy. But what does the scientific evidence say?

For those who don’t know, training on an empty stomach is a strategy with a history, used by cyclists, marathon runners and even triathletes to burn more fat during exercise and enhance the fat consumption process. So, are the benefits only linked to fat levels and body weight? No, there is actually much more to it.
Two years ago I decided to research this topic in-depth through my final master’s project. I worked with two athletes who ran a 10km race before the experiment. I recorded anthropometric measurements such as weight, skin folds, perimeters and diameters, as well as various race tests measuring metabolic and performance variables such as maximal aerobic capacity, blood lactate and speed.

The experiment lasted six weeks, ending with another 10km race. The results showed an improvement in body weight and body fat, in comparison with another subject who did not exercise on an empty stomach (though the difference was not too substantial). The really positive changes were shown in their competition thresholds – in other words, improvements that allowed them to run at a greater speed in the 10km race. Naturally, my conclusions were that this type of strategy can lead to an improvement in running performance during races.

There is a great deal of evidence to support this, although admittedly the sample almost always consists of athletes (cyclists, triathletes, etc.) as opposed to people who are relatively active and wish to lose a little body fat. The scientific evidence  talks  about positive results in terms of an improvement in the fat oxidation rate, an increase in the enzymes involved in lipolysis, a decrease in intramuscular triglycerides (fat) and an increase in the hormones that stimulate fat mobilisation (lipolysis), but practically no studies (except 1 or 2) showed a direct benefit in terms of body fat loss. In other words, there is no truly viable scientific evidence to show that this type of strategy increases body fat loss.

The simple reason is that, regardless of the level of fat mobilisation during training on an empty stomach, the body CANNOT use all these fatty acids as energy, so all the fatty acids that were mobilised in your blood will be stored again as fat. This is because the recommended intensity for this strategy does not require much energy, as in High Intensity Interval Training, for instance.

In my opinion this strategy has been misunderstood, because although it is true that it can lead to positive results in the performance of athletes (running times, submaximal capacity, etc.), it is not ideal for active people who exercise a few days a week and wish to lose some excess body fat and weight. Furthermore, there is little scientific evidence to support its benefits in terms of body composition.

But not everything is negative. Cardiovascular exercise on an empty stomach can help prevent problems such as diabetes and can activate us in the morning, allowing us more free time during the rest of the day.

So, if you don’t mind working out on an empty stomach, here’s what I recommend:

  • Training that consists of low to moderate intensity cardio, such as power walking or jogging.
  • Including at least one portion of carbohydrates in your last meal of the day before.
  • Recovering after training or breakfast by taking a whey protein with L-Glutamine to improve muscle recovery, such as the excellent Premium Whey by Weider.

With other forms of cardiovascular exercise, like High Intensity Training, which affords plenty of evidence in terms fat loss, it is best not to train on an empty stomach.

I hope this article has helped you learn a little more about this topic so you can draw your own conclusions.

Your WEIDER® Team