We continue to explore fuel used for energy and intensity of activity to address whether or not there is an ideal, so-called, “fat burning zone.”
If we understand that at rest our bodies prefer to use fat over carbs, we also need to understand that there is NO MAGIC AMOUNT OF EXERCISE TIME OR INTENSITY LEVEL WHERE WE BEGIN TO USE FAT AS THE PRIMARY FUEL. During all times of exercise, fat is being used as a fuel but it is always used along with carbohydrates. As the intensity increases, fat is still used, but just in a smaller percentage.
Do the math; here's a comparison of two different exercise treadmill plans for the same client, aged 30:
At 50% VO2 max- 200 calories burned (50% fat), 100 calories from fat. 70% VO2 max - 310 calories (40% fat), 124 fat calories. (Aerobic capacity is measured by the amount of oxygen that can be delivered to the muscle cell compared to the amount of oxygen used by the muscle cell to make energy for muscle contraction. This is referred to as VO2 max.) This equation shows us that even though the % of fat being used is reduced with higher intensities, the total amount of fat being burned is increased because the TOTAL CALORIC EXPENDITURE IS INCREASED.
For optimal fat reduction results, the focus should be to exercise as hard as possible for as long as possible to increase the total number of calories expended and the total amount of fat used.