First we need to clarify what is meant by this. We talk about burning fat when fat is actively used as an energy source. Unlike the two other energy sources, namely creatine phosphate and carbohydrate, fat is metabolized primarily at low intensities. On the other hand, fat provides energy over a long period of time.
It is now clear that fat can be burned, but only under certain conditions.
The main criteria are, as already mentioned, a low intensity and a long period of time. Fat is metabolized from a few minutes on, but only to a small extent. From about the twentieth minute onwards, fat becomes the main source of energy supply. From this point on, training becomes effective in terms of duration and fat metabolism.
The second parameter, i.e. intensity, can be calculated using a simple formula: (220 - age in years) x 0.65 = fat burning pulse. Thus the intensity is defined by the pulse. The best way to check your pulse during exercise is with a heart rate monitor or chest strap.
Conclusion: If you want to burn fat, you have to engage in continuous activity at a comparatively leisurely pace over a long period of time.