A larger total quantity of calories AND fat is expended during higher intensity exercise. The total number of calories expended, NOT the percentage mixture of carbohydrate, protein and fat oxidized determines the effectiveness in weight loss.

It’s important to realize the difference between PERCENT of energy expended and TOTAL energy expended. While it is true that the higher the intensity, the lower the PERCENT the contribution from fat, the TOTAL amount of energy expended is more significant to weight loss. Although fat makes a greater PERCENTAGE contribution to total energy metabolism during light versus intense aerobic activity, a larger TOTAL amount of fat is expended during higher intensity aerobic exercise.

For example:

Intensity Level     Total Calorie Expended     Percent from Fat     Calories from Fat

High (30 min.)                      500                                20%                            100

Low (30 min.)                       100                                60%                              60