> Microwave ovens do not cook food from the inside out. 2.45 Ghz microwaves can only penetrate approximately 1 centimeter (0.39 in) into most foods. The inside portions of thicker foods are mainly heated by heat conducted from the outer portions.
I think the main reason this myth persists is stuffed/filled food items such as pizza rolls, burritos, Pop Tarts, Hot Pockets, etc.. With these, there's typically an outer layer that is thermally insulating and lower-density, while the filling is more thermally conductive and higher-density (water/fat). This means that even if the temperature is uniform, the filling will be perceived as much hotter than the outer layer.
I think the main reason this myth persists is stuffed/filled food items such as pizza rolls, burritos, Pop Tarts, Hot Pockets, etc.. With these, there's typically an outer layer that is thermally insulating and lower-density, while the filling is more thermally conductive and higher-density (water/fat). This means that even if the temperature is uniform, the filling will be perceived as much hotter than the outer layer.