I heard my body burns more fat at low intensity levels (50-60% of MHR- max heart rate) is this true?
This is a great question that I hear from clients and students on a regular basis. As exercisers we are further confused by the fact that cardio machines at many gyms still have a chart that shows the fat burning zone as a low intensity level, usually just above a walking pace, and a performance zone as the higher intensity levels. Of course we would all like to believe that the best exercise for fat burning is an easy walk or light cardio. This would make the road to fat loss much easier!
The truth is, yes, your body does burn a higher percentage of fat as a fuel source when exercising at lower intensity levels. However, once you begin moving quickly or increasing your intensity, you suddenly present your body with a fuel dilemma. Fat cannot provide energy as quickly as carbohydrates so when the body needs to move quickly, or needs to move a heavy object, it needs immediate energy, and that’s where carbohydrates come in. They may not provide as much energy, but they certainly provide it much faster than fat.
So as you progress from standing still, to walking, to jogging, to an all-out sprint, your body begins to tap into carbohydrates more and more, while reducing its use of fat as a fuel. Of course, during this entire progression, you’re burning more overall calories too. So while the percentage of fat used as a fuel is decreasing, the total fat calories you burn might still be increasing.
For example, if you burn 200 calories per hour while walking and burn 60% fat, then you burn 120 fat calories per hour. But if you burn 600 calories per hour during interval training and only burn 40% fat during that time, you still burn 240 calories of fat per hour, twice as much as when you were walking.
So to answer our initial question, “Does my body burn more fat at low intensity levels?” The answer is yes and no your body does burns a higher percentage of fat at lower intensity levels but a higher overall amount of fat at higher intensity levels. So unless you have 2-3 hours of free time to spend walking everyday it may be best to ramp up your workouts and burn the same amount of fat in a shorter high intensity workout.
This type of high intensity workout also has many other benefits including increased aerobic capacity, increased anaerobic threshold, EPOC (extended calorie burn for 24-36 hours after the workout) and increased muscular strength to name a few. Stay tuned for next week’s post for more information on these benefits.
Jessica Rose
Motion Fitness and Massage 