Yeah, that's right, Make it a belief slider. Energy restoration rates should not change but the amount of hunger consumed to regenerate that would be affected by this slider. The middle would reflect the current metabolism.
Abstracting this as a 'belief' shouldn't be much of a stretch.
This would give noobs greater survivability and reasonable rates of development to more advanced players. Given this, make water preform as tea, and tea preform as Pacho suggested (Reduced stamina consumption for activities as a 'status' effect) and given this I can buy not having a rapid consumption method.