title: Brain white matter expansion in human obesity and the recovering effect of dieting.
abstract: OBJECTIVE
  Obesity is associated with several metabolic abnormalities. Recent studies suggest that obesity also affects brain function and is a risk factor for some degenerative brain diseases. The objective of this study was to examine the effects of weight gain and weight loss on brain gray and white matter structure. We hypothesized that possible differences seen in the brains of obese subjects would disappear or diminish after an intensive dieting period.
  
  
  METHODS
  In part I of the study, we scanned with magnetic resonance imaging 16 lean (mean body mass index, 22 kg/m(2)) and 30 obese (mean body mass index, 33 kg/m(2)) healthy subjects. In part II, 16 obese subjects continued with a very low-calorie diet for 6 wk, after which they were scanned again. Regional brain white and gray matter volumes were calculated using voxel-based morphometry.
  
  
  RESULTS
  White matter volumes were greater in obese subjects, compared with lean subjects in several basal brain regions, and obese individuals showed a positive correlation between white matter volume in basal brain structures and waist to hip ratio. The detected white matter expansion was partially reversed by dieting. Regional gray matter volumes did not differ significantly in obese and lean subjects, and dieting did not affect gray matter.
  
  
  CONCLUSIONS
  The precise mechanism for the discovered white matter changes remains unclear, but the present study demonstrates that obesity and dieting are associated with opposite changes in brain structure. It is not excluded that white matter expansion in obesity has a role in the neuropathogenesis of degenerative brain diseases.
authors.affiliation: Department of Neurology, University of Turku, P.O. Box 52, FIN-20521 Turku, Finland. toivo.haltia@tyks.fi
authors.forename: Lauri T
authors.initials: LT
authors.lastname: Haltia
authors.forename: Antti
authors.initials: A
authors.lastname: Viljanen
authors.forename: Riitta
authors.initials: R
authors.lastname: Parkkola
authors.forename: Nina
authors.initials: N
authors.lastname: Kemppainen
authors.forename: Juha O
authors.initials: JO
authors.lastname: Rinne
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nuutila
authors.forename: Valtteri
authors.initials: V
authors.lastname: Kaasinen
mesh_terms: D050154:Adiposity / Q000502:physiology; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D001921:Brain / Q000473:pathology*; D003627:Data Interpretation, Statistical; D004038:Diet, Reducing; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009765:Obesity / Q000178:diet therapy* / Q000473:pathology*; D049629:Waist-Hip Ratio; D015431:Weight Loss
chemical_list: D001786:Blood Glucose