The mass that is pushed backwards is taken from the atmosphere or carried in the airplane. A wing produces lift by the way it disturbs the molecules in the atmosphere when moving through the air. A propeller can produce thrust by pushing the atmospheric gas from in front of the airplane back behind it. An inflated balloon that is released in a room pushes the gas from inside it out through a nozzle. This does not require mass from the atmosphere to generate thrust.
Energy is needed to supply the force that accelerates the airplane.
The energy must be stored until the force is needed. Chemical energy is often stored, and released in a controlled reaction at the appropriate time. This chemical energy is in the form of fuel. Storing fuel on an airplane adds weight. This added weight will require more lift.