  The formula for the temperature dependence of the effective mass of a $^{4}%
$He atom in the superfluid and normal phases is obtained.\,\,This expression
for the effective mass allows one to eliminate infra-red divergences, being
applicable at all temperatures, except for a narrow fluctuation region
0.97~$\lesssim T/T_{\rm c}\leq1$.\,\,In the high and low temperature limits, as
well as in the interactionless limit, the obtained expression reproduces the
well known results.\,\,The temperature dependence of the heat capacity and the
phase transition temperature $T_{\rm c}\approx$~2.18~K are calculated, by using
the formula obtained for the effective mass.\,\,In the framework of the
approach proposed in this work, the small critical index $\eta$ is determined
in the random phase approximation.\,\,The obtained value corresponds to the
well known result.
