Complex sentence: Fried rice is believed started as a way to avoid throwing away and wasting precious food, as a method to pleasantly and safely consume leftovers through stir-frying, since the heat from cooking prevents the propagation of dangerous microbes.
Split into simpler sentences: Fried rice is believed started as a way to avoid throwing away and wasting precious food. As a method to pleasantly and safely consume leftovers through stir-frying, since the heat from cooking prevents the propagation of dangerous microbes.