There is good evidence that you cannot simply burn off calories this way. That the body will reduce energy consumption at other times to compensate. The overall effect of exercise on energy consumed by the body is minimal. That is, exercise does not build metabolism and in the absence of increased food intake exercise will result in lower metabolism. Try reading Good Calories, Bad Calories. I've been surprised by the number of things I have thought or been taught that are directly contradicted by the experiments reported in this book.