There is an exercise intensity that is called the fat burning zone (which is at about 50% HRmax) where most of the energy your body uses comes from fat rather than carbs. HOWEVER exercising at a slightly higher intensity and modifying eating habits (as Bad Juju said) will have better long term results and improve your CV fitness at the same time BECAUSE though the proportion of fat burnt is less the overall calories burnt is more and at the end of a higher intensity session you will have burnt more calories and hence fat. But you have to then make sure you don't ruin the effort by eating lots of unsuitable food afterwards.

I also don't have those scales as they seem grossly expensive for a fairly inaccurate result.