Though low intensity exercise may be of some help with weight loss and improving overall health, higher intensity exercise is more effective for burning fat. Higher intensity aerobic activity two to four times per week will help to increase muscle and decrease fat. The intensity of the exercise is determined by current fitness level: for someone who is sedentary, fast walking uphill may be fairly intense aerobic exercise, but for someone who is already in shape, running or fast cycling may be necessary to get the needed aerobic workout to burn fat.
Though weight lifting in itself does not necessarily burn fat, it does build muscle, and more muscle mass makes the body more efficient at burning calories and burning fat. Since muscle burns calories, combining higher intensity aerobic exercise with weight lifting is often more effective for fat loss than exercise alone. In addition, muscle is a large factor in the bodies metabolic rate, so increasing muscle will give some gain in overall rate of metabolism, or calorie and fat burning.