--most of the anti-epileptic drugs used for neuropathic pain (with the exception of Topamax, for some reason) tend to promote weight gain, both by causing some degree of fluid retention and by subtly shifting the metabolic balance is favor of "the hibernation response"--the quieting of the central nervous system tends to promote appetite and carb-craving, as if one were soon to settle down for a long winter's nap.

Many people on these meds (I was certainly one) realize they have to considerably adjust their diets to keep this effects under control--not that cutting back on carbs wouldn't be a good idea for most neuropathy sufferers anyway, and, indeed, for most people in general.