Cardio on an empty stomach: It’s touted as a way to burn more fat.
The principle behind this training technique is that in a fasted state your muscle glycogen stores are depleted, so your body is forced to metabolise fat as a source of energy. However, this is only realistically achieved at intensities between 50-70% of your maximum heart rate.
The truth is that exercising at a higher intensity (i.e. above that 50%-70% range) means that your body cannot breakdown body fat stores at a rate fast enough to supply your working muscles with energy. So your body then turns to the only other available source: Muscle tissue. This is where people often become catabolic, losing hard earned muscle because they don’t work within the correct heart rate range.
This is why our experts recommend that you only try this technique when you’ve reached your ideal weight and want to shed that last bit of stored body fat. In the meanwhile, the better option is to manage your daily calorie intake. Make sure you have enough energy when you hit the gym to do high intensity cardio training, like intervals, and compound movement weight training, to burn as many calories as you can per day. This will ensure you create a daily negative calorie balance that ultimately results in weight reduction (without the muscle loss!).