AEROBIC EXERCISE: INTENSITY FOR FAT BURNING

One of the most commonly asked question’s in the gym regards the exercise intensity a person should train at if his or her main goal is to lose weight, or more precisely, burn fat.  Exercise intensity and duration are important factors concerning the total, and type (carbohydrate or fat) of calories burnt during an exercise session.  The higher the exercise intensity, the more carbohydrate will be used to fuel the exercise.  This is because the process by which the human body extracts energy from carbohydrate is a lot faster than that of fat.  In other words, using fat alone for energy is just too sluggish to keep up with the demands of high intensity exercise, and can therefore only partly contribute to the overall demand.  However, a higher proportion or percentage of fat is used as energy compared with carbohydrate at lower exercise intensities.  On this basis it would appear prudent to exercise at lower intensities, as you would appear to burn off more, or at least a higher percentage, of body fat.  However, it is more important to look at the whole calorie burning process a bit more closely.  We will look at two exercise sessions of either walking or jogging for 20 minutes:

 

WALKING (20 mins)

Calories burnt per minute = 5 cals

Total calories burnt = 100 cals

Percentage of calories burnt from fat = 80% = 80 cals

Percentage of calories burnt from carbohydrate = 20% = 20 cals

 

JOGGING (20 mins)

Calories burnt per minute = 10 cals

Total calories burnt = 200 cals

Percentage of calories burnt from fat = 50% = 100 cals

Percentage of calories burnt from carbohydrate = 50% = 100 cals

 

From this we can see that even though a higher percentage of fat was burnt during walking (80%) compared to jogging (50%), the total calories burnt in the same time scale was twice as high during jogging.  The total fat calories burnt during jogging was also higher than that of walking.  For weight loss purposes, the most important thing you can do is to create a negative energy balance:

ENERGY IN (food and drink)  <  ENERGY OUT (metabolism, physical activity) = WEIGHT LOSSpressSportsIndustry

Although the equation is over simplistic, it does demonstrate that it is the total calories burnt during physical activity that is of primary importance to weight loss.  This does not mean that low intensity exercise does not have a place in a weight loss program, but that if time is a constraint then choosing an aerobic exercise of a slightly higher intensity may incur greater caloric burning benefits.  Low intensity exercise like walking has the benefit of being less stressful and can be partaken in much more frequently and should be cycled in with higher intensity exercise if you are training more than three times per week.  Remember to always train within your own boundaries, build up slowly, and enjoy yourself.  It is of more benefit for you to participate in exercise at an intensity you feel you can stick with and turn into a habit, rather than push yourself too hard and end up exhausted, sore, or injured, and consequently deciding that exercise isn’t for you.

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