  We have performed deep imaging of a diverse sample of 26 low surface
brightness galaxies (LSBGs) in the optical and the near-infrared. Using stellar
population synthesis models, we find that it is possible to place constraints
on the ratio of young to old stars (which we parameterise in terms of the
average age of the galaxy), as well as the metallicity of the galaxy, using
optical and near-infrared colours. LSBGs have a wide range of morphologies and
stellar populations, ranging from older, high metallicity earlier types to much
younger and lower metallicity late type galaxies. Despite this wide range of
star formation histories, we find that colour gradients are common in LSBGs.
These are most naturally interpreted as gradients in mean stellar age, with the
outer regions of LSBGs having younger ages than their inner regions. In an
attempt to understand what drives the differences in LSBG stellar populations,
we compare LSBG average ages and metallicities with their physical parameters.
Strong correlations are seen between a LSBG's star formation history and its K
band surface brightness, K band absolute magnitude and gas fraction. These
correlations are consistent with a scenario in which the star formation history
of a LSBG primarily correlates with its surface density and its metallicity
correlates both with its mass and surface density.
