Training in a state of low carbohydrate availability can enhance the mitochondrial adaptations of our muscles. This means that we can increase the capacity to use fat as a fuel.

As a result, we use less carbohydrate during moderate, steady state exercise and this spares our muscle glycogen stores  for times when we place higher demands on our energy systems and are exercising at higher intensities. It also aids weight management by helping us to reduce our fat stores.

What are the drawbacks?

However, it’s not all plain sailing and there are two main drawbacks to fasted training:

• You will not be able to train as quickly (the intensity of your training session can be compromised) as you would on carbohydrate as you cannot produce energy from fat fast enough (the body is slower to convert fat and protein into energy, compared to carbs), while low liver glycogen and blood glucose levels will also have an effect. As a result, it is difficult to maintain high intensity exercise for a prolonged period of time in a low carbohydrate state.
• Your immune system relies on carbohydrate to function. Prolonged endurance exercise causes a drop in your immune function and low carbohydrate availability only makes this worse. This can leave you more prone to coughs and colds.

With that in mind, when and how should you use fasted training to achieve the maximum benefit?