Your body uses two primary nutrients for fuel: glucose and ketones. Most people use glucose for fuel; this is because the average person has a carbohydrate based diet. If you want to burn fat fast as hell, however, put your body into a state of ketosis. What this means is that your body’s primary source of energy is no longer carbohydrates, but fat. In other words, you’ll literally be burning your own fat supplies for energy.
Here's something else most people probably don't know: Fidgeting is good for you. It's considered a nonexercise physical activity, and it's an important way to burn energy. You get more health benefits if, in addition to exercising, you are a more fidgety, more active person the rest of the day. This means gesturing while you're talking, tapping your foot, just moving around.