When you workout longer than a certain time you burn muscle. Your body breaks it down to use it for fuel. When you train sprint intervals your goal is not to burn "X" amount of calories, but rather to stimulate your body to increase your metabolism which will burn more throughout the rest of the day. You will become much leaner.
Look at a picture of Carl Lewis and other sprinters. Their bodies are very lean and muscular. http://www.carllewis.com/
If you look at a marathon runner, like Dan Browne, they have lost a lot of muscle due to their distance running and are still a bit flabby(not over fat) due to the need for storage. http://danbrowne.com/
The more aerobics you do, the more your metabolism slows down and the more
efficient your body is at storing fat.
Why it works to store fat: Your body will actually use fat as fuel, and learn how to store it in order to make sure it has enough, during cardio exercise over 20 minutes (like when you hear that you should be in the "fat burning zone") which will create the perfect effect that we DON'T want for the other 23 hours of the day - which is fat storing mode.
Yes, your body will adapt to become efficient at storing fat.
This type of workout will do very little to increase your metabolism either. You'll burn off muscle, decreasing your lean muscle mass, and actually slow down your
Going to the gym, or hitting the pavement, will ultimately be you spending countless hours doing aerobics, burning off muscle, and turning your body into a fat storing machine! This is a perfect way to gain some body fat!
To get lean and increase your VO2 Max:
Do interval training instead of steady state aerobics to increase your metabolism
and get your body revving to burn fat all day long. So, instead of walking or running on a treadmill at the same pace for 30 minutes, you'd walk(or jog) two minutes then run(or sprint) for a minute or two, then walk(or jog) again. Alternate between high and low intensity. You can do the same on an exercise bike or whatever activity you choose. This works extremely well for fat loss! PLAIN AND SIMPLE.