Objective: Obesity and decreased physical health are linked to deficits in several cognitive domains. The broad range of cognitive problems linked to obesity suggests a global mechanism that may interfere with multiple neural systems. We examined how variation in body mass index (BMI) is associated with the microstructural integrity of fiber connections in the human brain.
Methods: White matter structure was measured using diffusion tensor imaging in 28 participants (mean age = 30 years) with BMI scores ranging from normal weight to obese (19.5–45.7 kg/m2) based on standard BMI criteria.
Results: Using a whole-brain voxelwise analysis, we found that, across participants, the fractional anisotropy of white matter voxels parametrically decreased with increasing BMI (63% of white matter voxels). Midbrain and brainstem tracts were among the pathways most strongly associated with obesity (r = −0.18 to −0.33, df = 27, all p values < .05). We also observed a weaker overall diffusion signal in individuals with higher BMI than controls with normal weight (r = −0.14 to −0.71, df = 27, for 67% of fiber pathways tested, all p values < .05). After controlling for this decrease in general diffusivity, we found that decreases in fractional anisotropy stemmed from both a decrease in axial diffusivity (p < .05) and an increase in radial diffusivity (p < .05).
Conclusions: Our results show that increased BMI is globally associated with a reduction in white matter integrity throughout the brain, elucidating a potential mechanism by which changes in physical health may influence cognitive health.
From the Learning Research and Development Center (T.D.V., W.W.S.), Department of Psychology (A.M.W., W.W.S., K.I.E.), Department of Health and Physical Activity (J.M.J.), and Weight Management and Wellness Center (D.L.R.), University of Pittsburgh, Pittsburgh, Pennsylvania.
Address correspondence and reprint requests to Timothy D. Verstynen, PhD, Department of Psychology, 342c Baker Hall, Carnegie Mellon University, Pittsburgh, PA 15213. E-mail: email@example.com
T.D.V. and W.W.S. were supported by a Defense Advanced Research Projects Agency contract (NBCHC070104). K.I.E. was supported by a Junior Scholar Award from the Pittsburgh Claude D. Pepper Older Americans Independence Center (P30 AG024827) and the University of Pittsburgh Alzheimer’s Disease Research Center (P50 AG005133). A.M.W. was supported by Award Number T32GM081760 from the National Institute of General Medical Sciences. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Defense Advanced Research Projects Agency, the National Institute of General Medical Sciences, or the National Institutes of Health.
None of the authors report any conflicts of interest.
Received for publication October 31, 2011; revision received March 12, 2012.