We all 'burn' a little bit of fat along with the glycogen our muscles use. If you're talking about a low-carb diet to 'force' fat-burning, then it doesn't work the way you think it does. First, low carb causes you to lose water weight. Water weight may look like any other weight to the bathroom scale, but it's Good Weight if you're exercising. Lack of it means you're dehydrated. Secondly, while most of us have large reserves of energy via our body fat, it's not quickly accessible; meaning that it can only provide a trickle of energy compared to carbs. Muscles don't burn fat directly, your body has to convert it, which is an inefficient process at best. You cannot retrain your body's chemistry to do it more efficiently; you can only train it to 'get used to' the effects. When we're reduced to using only fat as fuel, it's called "bonk." Low-carb leaves your muscles depleted of glycogen, less able to sustain prolonged use, and makes recovery much slower.

The best way to lose weight is still to eat less. Don't be afraid of eating carbs; but make sure the ones you eat are complex and 'nutrient-dense.' Or, to put it another way, avoid sugar and if you want to weigh 150 pounds, eat like a 150-pound person.