Abstract
Either at rest or under the influence of exercise, the human body does not evenly utilize fats and carbohydrates for energy. The term crossover concept was developed in 1994 to explain factors associated with an observed fuel preference shift from fat to carbohydrate as exercise intensity is increased. This relatively new conceptualization has generated so much interest and controversy among researchers that, in 1997, the American Physiological Society sponsored a Point-Counterpoint forum on the topic during their Experimental Biology Meeting. The purpose of this brief review was to explain the crossover concept and explore some of the physiological mechanisms pertinent to the concept as they have since been described in the literature.