Here is an interesting study regarding energy consumption http://www.cell.com/current-biology/abstract/S0960-9822(15)01577-8?_returnURL=http%3A%2F%2Flinkinghub

Here is an interesting study regarding energy consumption http://www.cell.com/current-biology/abstract/S0960-9822(15)01577-8?_returnURL=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982215015778%3Fshowall%3Dtrue http://www.cell.com/current-biology/abstract/S0960-9822(15)0... Tldr days of high level of exercise does not linearly correlate to high level of energy usage. The body can somewhere(brain?) spend less energi to compensate the exercise.