The Fasted Cardio Myth Debunked.

The Fasted Cardio Myth Debunked.

For those who are looking to burn body fat it’s not uncommon for them to perform cardio on an empty stomach first thing in the morning. It’s believed by many that when fasted the absence of food reduces blood sugar and causes stored carbohydrate (glycogen) levels to decrease. When glycogen levels are low your body has a tendency to rely more on fat to fuel training sessions. In addition, fasting typically lowers insulin levels which enables the body to breakdown fat more effectively.

While in theory this sounds logical, the reality is that it doesn’t transfer to the real world. It must be noted that multiple studies have in fact shown that consuming carbohydrates before aerobic training can blunt fat oxidation and other research suggests that a greater breakdown of fat takes place when fasted compared to when fed.1,2,3  However, the rate of breakdown is higher than the rate at which your body uses those extra fatty acids for energy.2,4 This means that there are many fatty acids in the blood that the muscles don’t actually use. The result is that these fatty acids are pulled back into the fat cells after the training session has finished. In effect, you have deprived your body of fuel for no reason and ultimately end up exactly where you were to begin with! Moreover to burn body fat you need to create a calorie deficit over the course of days not on an hour to hour basis.

Perhaps most importantly for bodybuilders and those who are looking to maximise muscle mass, it seems fasted cardio has the potential to have a catabolic effect on muscle. Multiple studies have demonstrated that training in a glycogen depleted state significantly increased the amount of tissue proteins burned for energy during exercise.5,6 This of course is not optimal for building or maintaining muscle mass.

Therefore, it simply doesn’t stand to reason to sacrifice muscle development in attempt to burn a few extra fat calories especially when you want to be jacked! So the take home message is that if you want to maximise fat loss then fasted cardio isn’t necessary and in fact it may even hinder your muscular development. 

Leave a Reply