(22-06-07) Brain White Matter Expansion in Human Obesity andthe Recovering Effect of Dieting.

Haltia LT, Viljanen A, Parkkola R, Kemppainen N, Rinne JO, Nuutila P, Kaasinen V.

Department of Neurology, University of Turku, Turku, Finland, Turku PET Centre, Turku, Finland, Department of Internal Medicine, University of Turku, Turku, Finland, Department of Radiology, University of Turku, Turku, Finland.

Context and Objective: Obesity is associated with several metabolic abnormalities. Recent studies suggest that obesity affects also 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 (MRI) 16 lean (mean BMI 22 kg/m(2)) and 30 obese (mean BMI 33 kg/m(2)) healthy subjects. In part II, 16 obese subjects continued with a very-low-calorie diet for six weeks, after which they were scanned again. Regional brain white and gray matter volumes were calculated using voxel-based morphometry (VBM). Results: White matter volumes were greater in obese subjects compared to 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.

Source: J Clin Endocrinol Metab. 2007 May 29;

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