The best way to burn fat fast, naturally and in a healthy way is by increasing your metabolism.
Once you learn how to increase your metabolism you will find that you will burn fat quickly, and the fat will stay of permanently.
Increasing your metabolism is not hard and you can do it naturally.
The first thing you must understand is what having a slow metabolism will do to you...
When we lose weight, we also lose protein from our muscles.
The faster we lose weight (by cutting down too much on our calorie intake), the more protein is used for energy; and when you lose too much protein from your muscles the result is a slow metabolism.
This happens because your muscles need protein to grow and stay strong.
When protein is taken from your muscles, you lose muscle tissue.
Muscle tissues are metabolically active and burn calories (even at rest).
Your body needs calories to feed these metabolically active tissues so that it has energy to continue to burn calories.
The calories that are burned also come from the fat that is stored in your body.
So in other words, the more calories you eat, the more energy your metabolism has to burn the fat that is stored in your body.
Without the calorie intake, your metabolism has no energy therefore it will slow down and you will burn fat at a very slow rate (if you burn any at all).
Having energy is not the only reason for a fast or slow metabolism.
You see, when you significantly cut down on your daily calorie intake, your metabolism burns calories slower to prevent your body from starving.
Being that your body now doesn't know when you will feed it; your body will store the calories to be used later.
The calories that are stored, are stored as fat.
On the other hand, you need to learn how many calories (energy) to eat each day so that you won't consume too many calories and store fat.
You also need to learn about meal frequency and how to properly eat to increase your metabolism.