Not So Fast(ed), My Friend!

Many of the bodybuilders at my gym perform their cardio first thing in the morning, before they've eaten breakfast. They believe that this "fasted" cardio "burns more fat." Based on the available research, they're wrong. At best, they're burning the same amount of fat as they would if they performed their cardio after a meal. And, worse, they actually might be adversely affecting their hard-earned muscle mass while performing cardio in a fasted state.

As I described in a previous post (the Dinosaur of Cardio), high-intensity interval training (HIIT) is superior to moderate-intensity, steady-state cardio for fat burning, even though less fat is "burned" (oxidized) during the exercise itself. This is because more fat is oxidized over time. And this is the key to really understanding fat loss.

What really matters is the fat burned throughout the day, not just the fat that is burned during the exercise itself.Also, training status(how long someone has been training) and the intensity of the exercise must be considered.

It is true that some studies show that at very low-intensity cardio ( below 60% VO2max) fat loss is reduced by carbohydrate consumption prior to exercise. But this reduction  only occurs after a long time (one study showed a reduction after 80-90 minutes of exercise.) Unless you are unhealthy, the bulk of your cardio will be performed in excess of 65% VO2max.

 At moderate and high exercise intensities, there is no difference in fat oxidation between a fed or fasted-state. You will also be able to work harder during your exercise session if you are fed.

And for anyone who wants to build muscle, listen to this: a study showed a protein loss of 10% of the total caloric cost of exercise.

So, stop torturing yourself with that fasted cardio. Eat up, and burn more fat during and after your exercise session.