Many people who go the gym to burn body fat will generally go on the treadmill or stationary bike for about 45 - 60 minutes of intense aerobic exercise. New research has shown that high-intensity anaerobic exercise, such as interval type training or weight lifting, has greater impact on weight loss than aerobic exercise.
In addition to leading to greater weight loss, high-intensity  exercise can also be done in less time than an aerobic workout. A regimen of 20 minute interval workouts three times a week combined with strength training is all you need to get fit and burn body fat fast.
The reason for this is your body is very efficient at adapting,  the more aerobic exercise you do the better you will get at it. As your body adapts to the exercise your benefits will diminish, as you get used to the effort. With interval type training you give your heart and lungs a challenge with every session, resulting in rapidly increased fitness. High intensity training will help change your body's thermostat for burning calories through out  the day after your workout. Making interval type training the best way to burn body fat.
Interval training routine:
• Warm up before starting intervals
• Assess current conditioning and set training goals that are within your ability
• Start slowly. (for example: walk 2 minutes/ run 2 minutes) In general, longer intervals provide better results
• Keep a steady, but challenging pace throughout the interval
• Build the number of repetitions over time
• Bring your heart rate down to 100-110 bpm during the rest interval
• To improve, increase intensity or duration, but not both at the same time
• Make any changes slowly over a period of time