  We present a determination of the parton distribution functions (PDFs) of the
proton from HERA data using a PDF parametrization inspired by a quantum
statistical model of the proton dynamics. This parametrization is characterised
by a very small number of parameters, yet it leads to a reasonably good
description of the data, comparable with other parametrizations on the market.
It may thus provide an alternative to standard parametrizations, useful for
studying parametrization bias and to possibly simplify the fit procedure thanks
to the small number of parameters. Interestingly, the model reproduces key
physical features, such as a $\bar d$ distribution larger than $\bar u$, that
HERA data alone are not able to constrain when using more flexible
parametrizations. Moreover, polarized distributions are described in the model
by the same parameters of the unpolarized ones, giving us the possibility of
extracting both types of distributions within the same fit.
