To achieve an aerobic or cardiovascular benefit you have to sustain a duration of 15-60 minutes of continuous exercise (e.g. run, swim, bike). A typical pilates class does not challenge the cardiovascular system enough to elevate the heart rate to the prescribed level. The muscle toning and strengthening benefits of pilates are the perfect complement to such fat-burning activities as power walking, swimming or cycling. Essentially, the body awareness and improved self-image you’ll gain with pilates will probably do more to help you win the battle of the bulge than crash dieting and obsessive exercising will.