Why does the smell of hot sizzling food reach you several metres away, but the smell of cold food does not?

The smell of hot sizzling food reaches you several metres away because the particles of the aromatic substances in hot food have higher kinetic energy due to the increased temperature. 

This higher kinetic energy causes them to move faster and diffuse more rapidly through the air. Cold food particles have lower kinetic energy, move slower, and thus diffuse much slower, making their smell less noticeable from a distance.