where do all the dead bodies go?

Form (life) within flow (inception towards death) implies a state of dissolution aka "to break up, disunite, separate into parts". Living implies disunity; dying implies unity.

The issue in the above question...a body cannot be plural (bodies) or whole (all); only a partial unit (form) within whole singularity (flow).

cemetery

Bur-i-al (to bury within all) tempts one to ignore that all (flow) disinters each one (form). Few suggest land; air or water burials to distract many from natural L(and) A(ir) W(ater) aka the ongoing division of each from one another within the same motion.

dead people being fed to the living

It's the process of dying which consumes each living potential within, hence each ones struggle with hunger and thirst. To distract from the natural process...few artificially feed potential to potential to tempt possession aka appetite.

In short...few are composting many.

fast food

Being implies slow (life) within fast (inception towards death) food...struggling in-between hunger (need) and appetite (want). Fast food tempts one to ignore that slow being requires one to resist temptation, which fertilizes resistance.

Dissolved and down the drain.