There has been a lot of chatter lately about supposed benefits of doing fasted cardio for fat loss.
People believe that cardio, performed without eating prior to the workout, means less available energy to power the workout thus leading to the breakdown of fat to power the workout.
While this sounds logical and is true, to a certain extent, it’s not the whole story.
1. It’s well established that when you are in a fasted state, especially in the morning when you’ve been fasting for several hours, your capacity for work is decreased as well as your mental tolerance for physical activity. The result will be less effective training sessions.
2. You do, in fact, burn more stored fat during the workout. But permanent fat loss for the long term is not about how much fat you burn during the workout, but rather, about what happens as a result of the workout over the next 24 hours.
3. Your body’s preference is to hold on to fat as a fuel of last resort. So, while you may burn fat while in a fasted state, you’ll also burn muscle. The long term result of burning muscle for fuel is a slowing of your metabolism making it more likely you’ll gain the fat back.
4. Research indicates that while you may burn more fat during the exercise period, you burn significantly less fat in the 24 hour period following the exercise.
The conclusion drawn from the study: “When moderate endurance activity is done to lose fat, fasting before exercise does not increase lipid utilization; rather, physical activity after a light meal is advisable”. Paoli, et al (2011)
In short, fasted cardio doesn’t work for long term fat loss.