Lots of MD guys here. MD500E. Topped off, 2 thin souls.   

The fuel control adjusts on how high you raise the lever. The lever IS THE LOAD as far as the engine and rotor is concerned. If you normally fly at 70% or 80% or whatever percent torque, you will burn the corresponding amout of fuel for that torque setting, doesn't matter what you weigh. The engine and rotor system have no idea what the helicopter weighs, it just know what you're asking it to do with collective. Lighter weight may require less power on take off and landing, but it's insignificant in the big picture as hoving and climbs often require lots of power.