Astrocytes and microglia respond to noxious stimuli by a process known as reactive gliosis (RG). RG is characterized by morphological changes such as increased cell size, enlarged, lengthened processes, and an increase in proliferation. Previously, in mice fed a high-fat diet (HFD) the number of reactive astrocytes and microglia in the arcuate nucleus (ARC) was increased. Harrison et al. have found that mice which are chronically obese after 22 weeks of HFD feeding display RG levels in the ARC comparable to levels seen in age-matched chow fed mice. Furthermore, profound weight loss results in an increase in ARC related astrocytic RG. However, whether or not reactive gliosis plays a role in chronic obesity, or rather in the acute adaptation to the dietary environment, remains to be fully understood.