High intensity exercises are the most efficient means of burning calories. METs, or Metbolic equivalents, are a common way of expressing the relative intensities of exercises. Running, uphill walking, aerobics and cycling are high MET exercises, having METs greater than 6.
In addition to increasing frequency and intensity of exercise, reducing caloric intake also helps burn fat faster. Burning more calories than one consumes requires the body to use alternative sources of energy. This energy can come from burning fat. Maintaining this calorie deficit over time results in the body fat reduction, and increasing the size speeds the process. Building muscle also helps burn fat, as it increases basic metabolic rate.