HIIT training is the best fat burning method to date.
A HIIT workout utilizes timed intervals of work and rest. A variety of intervals can be used, however the most effective is the Tabata method of 20 seconds of work and 10 seconds of rest for 8 rounds.
It's best to choose a multi joint exercise like a squat push press or standing cable row to work several muscle groups at once. Muscles require energy to contract. Thus, the more muscles used, the more energy burned.
Choose a weight that is roughly 65% of your one rep max (1RM). The first couple of intervals will feel relatively easy. As you continue the cumulative effect will start to take it's toll. You should be struggling to reach the same number of reps during the last few rounds as you did at the beginning. If not, then bump up the resistance.
The short bouts of rest allow enough recovery to get in a few good reps before metabolic acid accumulates in the muscles and shuts them down.
Though both carbohydrates and fat are burned during this process your body will tap more into the carbohydrate stores throughout the workout. This is a necessary process to meet the demands of exertion.
It is AFTER the workout when the body leans more on elevated fat burning levels to satisfy metabolic needs. This is when the welcomed fat incinerating process takes place - which can last up to 36 hours depending on your efforts during the workout.
Combine this with a calorie conscious meal plan and watch your waistline shrink!