The Urban Trainer Blog - UK

Several years ago, certain individuals in the fitness industry seized upon the fact that low to moderate intensity exercise is fuelled predominantly by fat, and that an optimum fat burning rate had previously been identified at 65% V02 max. Since that time further research has shed a little light on the claims.

• The Fat Burning Zone (FBZ) is not the optimum exercise intensity for weight management, fitness or performance.
• Although a greater proportion of energy is derived from fat within the FBZ, total energy expenditure is greater with high intensity exercise.
• It is total energy expenditure, regardless of the source, that is paramount to achieve sensible weight loss via negative energy balance.
• Energy expenditure is greater both during and in recovery from high intensity exercise.
• The moderate intensity FBZ is unlikely to break the lower threshold to bring about a prolonged excess post-exercise oxygen consumption (EPOC).
• The prolonged EPOC component is fuelled by fat and may add an additional 30+kcal to each workout.
• It is unlikely that aerobic fitness will be maintained or improved within the FBZ.
• Training within the FBZ will not bring about the preferential metabolism of fat during exercise or higher resting metabolic rate enjoyed by endurance trained subjects.
• The variation in max heart rate undermines the use of prediction equations in exercise prescription (quite often the basic calculation will underestimate the actual by up to 10%).