  We examine the evolution of low-mass star and brown dwarf eclipsing binaries.
These objects are rapid rotators and are believed to shelter large magnetic
fields. We suggest that reduced convective efficiency, due to fast rotation and
large field strengths, and/or to magnetic spot coverage of the radiating
surface significantly affect their evolution, leading to a reduced heat flux
and thus larger radii and cooler effective temperatures than for regular
objects. We have considered such processes in our evolutionary calculations,
using a phenomenological approach. This yields mass-radius and effective
temperature-radius relationships in agreement with the observations. We also
reproduce the effective temperature ratio and the radii of the two components
of the recently discovered puzzling eclipsing brown dwarf system. These
calculations show that fast rotation and/or magnetic activity may significantly
affect the evolution of eclipsing binaries and that the mechanical and thermal
properties of these objects depart from the ones of non-active low-mass
objects. We find that, for internal field strengths compatible with the
observed surface value of a few kiloGauss, convection can be severely
inhibited. The onset of a central radiative zone for rapidly rotating active
low-mass stars might thus occur below the usual $\sim 0.35 \msol$ limit.
