The present work evaluates the effect of gap in the density-dependent one-body momentum distribution, \( n(k,\rho)\), at the Fermi surface on the calculation of the single-particle properties of nucleons, i.e., the momentum- and density-dependent single-particle potential and the nucleon effective mass, and also on the calculation of the ground-state binding energy of the selected closed-shell nuclei, i.e., 16O, 40Ca, and 56Ni. In order to do this, \( n(k,\rho)\) is constructed by use of the calculations of the lowest-order constrained variational method for the symmetric nuclear matter with the \( Av_{18}\) potential up to \( J_{max}=2\) and 5. It is shown that the gap in \( n(k,\rho)\) at the Fermi surface has no significant effect on the calculation of single-particle properties in the case of \( J_{max}=5\). In the relevant evaluation of the ground-state binding energy of selected nuclei, it is seen that the binding energy of 16O, improved by including \( n(k,\rho)\), is closer to the experimental data, contrary to 40Ca and 56Ni.