If your aim is to burn fat fast, taking traditional methods such as slow pace cardio and low calorie/carbs/fat diet won't help at all. Those approach may work at first, but as time passed, you'll notice that it'll give you even less progress for the very same efforts, sometimes you won't make progress at all. The reason for that is your body have made "adjustment" to match your monotonous diet or exercises, thus make them have less impact over time.

Those methods fail because they can’t fulfill the iron rule of fast fat burning: keeping your metabolic rate high at all time. Maintaining your metabolic rate continuously high will let you burn fat fast, keeping you from gain weight again, and ensure that your workout or diet effort continue to give you the best result every single day.

To maintain your metabolic rate continuously high, you must alter your monotonous diet and workout into something much more flexible, something which your body cannot expect and won’t have any chance to adjust itself with it. By "adjust" here I mean that your body will slowing its metabolic rate and storing fat instead of burn it.

Like I said above, the first step to burn fat fast is modifying your monotonous diet. It can be done by understanding the principe of calorie shifting and apply it to your meal plan. Fundamentally, you make sure that your calorie intake between meals keep varied; sometimes rich, sometimes low calorie. This calorie intake behavior is not something that your body can expect or adjust itself; as the result, you will have steady and high metabolic rate at all time.

There are several more in it though; merely altering your calorie intake will not do the job. You need carefully calculated meal plans that not only fulfill the calorie shifting requirement, but also make sure you stay healthy by eating all food groups (meat, vegetables, fruit, etc) and give you proper nutrient intake.

The second step to achieve fast fat burning is make sure that your workout will keep your body guessing. Basically, it share the same principle with calorie shifting theory; the method is known as high intensity interval training.

The basic of this method is every time you exercising, you must keep changing between high intensity and low intensity exercise instead of slow pace exercise for the whole session.

The easiest example for this is jogging; try slow jog for 2 minutes, followed by sprint for 1 minute, back to slow jog for 2 minutes, and so on. It's also possible to use distance; for instance: sprint for 50 yards, then rest for 1-2 minutes and sprint again; continue doing this 6-10 times. This principle can also be applied in other exercises: swimming, bodyweight exercises such as squat and pushups, biking, etc.

So here is the key of fast fat burning: apply calorie shifting in your daily meals and high intensity interval training in your exercise menu. You don't need to do the HIIT every day; on the other hand, you must apply calorie shifting in your daily meal plan.