[en] A model for the quantum Zeno effect based upon an effective Schroedinger equation originated by the path-integral approach is developed and applied to a two-level system simultaneously stimulated by a resonant perturbation. It is shown that inhibition of stimulated transitions between the two levels appears as a consequence of the influence of the meter whenever measurements of energy, either continuous or pulsed, are performed at quantum level of sensitivity. The generality of this approach allows one to qualitatively understand the inhibition of spontaneous transitions as the decay of unstable particles, originally presented as a paradox of the quantum measurement theory. (orig.)