From this NYT article, The Claim: Lack of Sleep Increases Weight:
We burn calories four ways. One of the ways is the burning of additional calories after the exercise session is over.
It has long been assumed that if you don’t head back to the gym a few days after you last session your positive results will begin to dwindle. Take a couple weeks off from running and you will find that that will usually be that case. Take a week or two off from weight training and you might find that you come back stronger.
Muscle tone or tonus is the slight contraction of muscle even when it is at rest. Muscle tone comes from having strong muscles. Athletes who look incredibly toned are that way because they are strong.
People exercise to look better, feel better and be healthier with much of the emphasis on looking better. Many stop when they are not able to magically transform the way their body looks. Their expectations for changing how they look are unrealistic. Flashy fitness ads and promises of suspect exercise devices reinforce these unrealistic expectations.