Can fasted cardio help you burn fat?

In the modern world, we are all looking for quick ways to lose fat and as more of us ask the question ‘how to lose weight?’ the answers are becoming more diverse. This week we’re looking at the pros and cons of the latest popular fat burner – fasted cardio.

The Concept

In recent years fasted cardio has become a hot topic and perhaps this is because of its perceived simplicity. When you fast (sleeping for example) your blood sugar and glycogen stores fall. This drop in blood sugar is combined with a decrease in insulin levels, which should theoretically help the fat-burning process since insulin supresses fat metabolism. Therefore if you do your cardio on an empty stomach, your body will be forced to tap into your stored energy sources such as fat molecules.

When we combine cardio with fasting, we therefore have ourselves a fat burning route to lean. So far so good, but unfortunately a straightforward theory isn’t always correct, especially considering that nothing in physiology or biochemistry of the human body is that simple.

The Research

There are a number of research pieces that attempt to answer the question around cardio on an empty stomach but as expected, the results are varied. A study published by the British Journal of Nutrition found that those who did fasted cardio burned 20 percent more fat than when they did cardio with a meal beforehand. On the other hand the International Journal of Sport Nutrition and Exercise Metabolism found that fed participants showed an increase in oxygen consumption (VO2) and substrate utilization (fat usage) both during the workout and in the 12 to 24 hours post workout versus participants who fasted.

So now we’re all suitably confused on fasted cardio lets take a look at this from a different perspective. The reality behind fat loss is that it isn’t simply a switch we can flip depending on the kind of exercise we do. There are also metabolic, dietary and lifestyle factors at play. Therefore, we cannot simply jump to the conclusion that fasted cardio is the best for burning fat since these factors can affect the results. It must also be noted that the majority of studies focussed on calories burned during exercise. As many of us know, the real benefits of exercise such as high intensity cardio usually come to us after training and this isn’t always factored into the theory.

What do we recommend?

In all, we do believe fasted cardio is a good way to reach those marginal gains for anyone who has normal to low fat levels. For example, if you have a small amount of fat that won’t shift in hard-to-attack areas, exercising in a fasted state could spark those resistant fat cells to release stored fat so it can be burned for fuel.

We also must remember that your body breaks down amino acids into glucose overnight, so fasted morning cardio mobilizes more fat but also potentially more amino acids for fuel, this is not ideal if building muscle is your primary goal. However, there’s no need to worry as long as you consume a fast-digesting protein like whey, after your cardio to build those amino acids back up. Equally, if you want to make sure your gains are lean, you can check out our Diet Whey too.


The Supreme Nutrition Team