Exercise is often (wrongly) assumed to be extremely important for weight loss. Watching popular shows such as ‘The Big Loser’ often portray exercise as the most important factor in weight loss. Courageous Drs. Malhotra, Noakes and Phinney recently pointed this out in a recent editorial. The reason for this commonly made error lies in the misunderstanding of Total Energy Expenditure or ‘Calories Out’. Consider the following:
Fat gained = Calories In – Calories Out
This is sometimes called the First Law of Thermodynamics. It’s funny how nutritionists alwaysreference thermodynamics, drawn to as children to amusement parks, but physicists who spend decades studying thermodynamics never, never, never talk about calories. Like the smelly annoying kid with no friends, calorie-enthusiants want to pretend that nutrition, too, is a ‘hard science’ like physics with ‘inviolable’ laws. Sad, and more than a little pathetic. Any who…
In this equation – we can easily measure “Fat Gained” and “Calories In” The main focus, then should be on the ‘Calories Out’ part of the equation, not the ‘Calories In’. This is what exercise enthusiasts have always preached. However, what is the ‘Calories Out’ portion of the equation?
The amount of calories used in a day (Calories Out) is more accurately termed total energy expenditure (TEE) – the sum of basal metabolic rate (BMR), thermogenic effect of food (TEF), non-exercise activity thermogenesis (NEAT), excess post-exercise oxygen consumption (EPOC) and, of course, exercise.
TEE = BMR + TEF + NEAT + EPOC + Exercise
The key point here is that TEE is not the same as exercise. The overwhelming majority of TEE is notexercise but the BMR: metabolic housekeeping tasks such as breathing, maintaining body temperature, keeping the heart pumping, maintaining the vital organs, brain function, liver function, kidney function, etc.
The second mechanism of compensation relates to a reduction in non-exercise activity (NEAT). If you exert yourself all day, you are less likely to exercise in your free time. The Hadza, who were walking all day, reduced their physical activity when they could. In contrast, those North Americans who were sitting all day probably increased their activity when given the chance.
This principle also holds true in children. Students aged seven and eight years who received physical education in schools were compared to those who did not.16 The physical education group received an average of 9.2 hours per week of exercise through school, while the other group got none.
Total physical activity, measured with accelerometers, showed that there is no difference in total activity over the week between the two groups. Why? The PhysEd group compensated by doing less at home. The non-PhysEd group compensated by doing more when they got home. In the end, it was a wash.
In addition, the benefit of exercise has a natural upper limit. You cannot make up for dietary indiscretions by increasing exercise. You can’t outrun a poor diet. Furthermore, more exercise is not always better. Exercise represents a stress on the body. Small amounts are beneficial, but excessive amounts are detrimental