By Al Sears, MD
Don't make the mistake of thinking that burning fat during a cardio workout will keep the fat off. Long-duration cardio will stimulate your body to build back any fat burned. And if you do it long enough, the unnatural stress will give you a stooped, weak, arthritic, tired, and old body shape.
Your body makes metabolic "decisions" based on its reading of your environment - which means that the sustainable benefits of exercise happen after you stop exercising. During long-duration workouts, your body thinks to itself, "I'm burning fat. I need to make sure I have enough fat - at all times - so I don't run out of fuel during these stressful periods." As a result, your body will actually start to make and store more fat as soon as you finish the workout. This is your body's defensive response to an unnatural condition you created.
To burn fat and keep it off, you need to give your body the right challenge - a challenge that triggers your body to stop, not...