So, Kat asked me how beneficial and safe it was to do fasted cardio. I laughed because it’s SUCH a controversial subject. I’ve read some fairly heated debates from some of the top pros in the industry arguing both sides with points that are all really compelling. Below, I’ll provide a link to one of my favorites but if you’re not interested in reading a lot about the science behind it, the two basic schools of thought are as follows:
Pros: Proponents say that you will burn more fat than if you eat beforehand.
Your body stores glycogen to use as its preferred source of fuel during exercise. The idea behind fasted cardio is that your glycogen stores would be somewhat depleted first thing in the morning after fasting overnight. Having less glycogen available to use as fuel, it would switch and use fat stores as its next source of fuel, allowing for a greater amount of actual fat being burned.
The key to this being successful seems to be that the intensity level of the exercise stays in the low to moderate range. When your body exercises at a low intensity, it uses more fat than carbohydrate.
Cons: Opponents say you’re burning less calories and that it’s a recipe for muscle wasting.
Because the work is easier, you’re not burning as many overall calories so you’d have to work for a longer period of time than if you were training hard. You shouldn’t run sprints or do some other high-intensity exercise as the lack of glycogen in your system wouldn’t allow for it. This makes it a definite no-no if you’re training for a race, endurance event, etc. It’s also said that all fasted cardio manages to do is burn off muscle, rather than fat.
My take is that like most things, there are no absolutes. If you spend some time looking, there are studies to support both theories.
The bottom line for me? I train with a team of the most perfect bodies in the world and most do some form of fasted cardio or another first thing in morning. That’s good enough to convince me …when done properly and depending on your goals, of course!
How’s that for a clear as mud answer?