We have shown previously that genetically instrumented obesity types that associate with lower grey matter volume (‘metabolically unfavorable’ and ‘neutral adiposity’), are associated with higher levels of inflammation marker C-reactive protein whilst ‘metabolically favorable’ obesity which showed a suggestive association with higher grey matter volume, was not; suggesting inflammation may be related to the grey matter volume-decreasing mechanism [26]. This evidence concerns the gene CRP and obesity due to melanocortin 4 receptor deficiency.