--is that, in the process of downregulating the responsivity of the central nervous system, gabapentin and a number of other anti-seizure drugs induce the body into believing it is the time of year to semi-hibernate, and this physiologically comes with the desire to "fatten for the winter", as it were.

Many people report the tendency, as the days grow shorter, to be sleepier and want to eat more carbohydrates; this is thought at least in part to be due to the nervous system's response to shortening daylight hours as mediated through the pineal gland and hypothalamus--energy needs to be stored and conserved for the coming colder months. Apparently the anti-seizure drugs upregulate this process to some extent.