A:  University of California, Berkley, researcher Dr. George Brooks developed the crossover concept of exercise metabolism, showing that the body uses fat as a fuel below 65 percent of maximum effort and mainly carbohydrates at higher exercise intensities. British scientists confirmed this finding and identified 63 percent of max as the intensity resulting in the greatest fat use. Many personal trainers and aerobic equipment manufacturers have mistakenly interpreted this information to mean that training at low intensities is best for losing body fat.

Swedish studies have shown that 24-hour fat use is greatest following intense exercise. Studies from Laval University show that people who exercise intensely lost more weight and body fat that those who exercised at lower intensities. High-intensity exercise increases muscle mass, burns more calories and triggers greater post-exercise metabolism and fat use. Train intensely to lose fat.

(Int J Sports Med, 24: 603-608, 2004)