Exercise Moderately With Aerobics & Weights or Calisthenics.
Gradually Increasing The Intensity, As Fat Is Lost
When one is severely overweight, it is probably best to start their fat burning phase with low intensity aerobics and weight training, to ensure that the body is not placed under undue stress at this early stage. For the significantly overweight (those over 25 percent body fat in males and 30 percent in females) it is best to work moderately as a way in which to gradually ease into a higher intensity program. 
A walking program would be a healthy start!  
May you have great success!