  We present an ab initio study of inclusive semileptonic decays of heavy
mesons from lattice QCD. Our approach is based on a recently proposed method,
that allows one to address the study of these decays from the analysis of
smeared spectral functions extracted from four-point correlators on the
lattice, where the smearing is defined in terms of the phase-space integration
relevant to the inclusive decays. We present results obtained from gauge-field
ensembles from the JLQCD and ETM collaborations, and discuss their relation
with theoretical predictions from the operator-product expansion.
