... which works as long as one does not consume more calories that the total amount of calories one burns (i.e. is in a caloric deficit). The real issue is that individuals who suffer from excessive weight tend to be in a caloric surplus
Body will always switch to burning mostly fat after a prolonged period of physical activity which studies suggest for moderate level of constant physical activity happens somewhere around 90 minute mark. There are no magic bullets.
How would you know this?