High body mass index (BMI), waist-to-hip ratio (WHR), and fat mass may be indicative of gray matter atrophy, according to a new study published in Neurology.

The UK Biobank Study was used to collect cross-sectional data from 9652 participants (age, 55.4 ± 7.5 years) from England, Wales, and Scotland. Researchers obtained obesity-related data, including body weight, fat mass, BMI, and waist and hip circumferences. Participants had also undergone magnetic resonance imaging scans, which provided data on total gray and white volumes that were incorporated into the analysis. Body weight data were assessed to determine whether any relation existed between BMI and WHR with brain-related changes.

For every 1 standard deviation unit increase in BMI, gray matter volume decreased (β coefficient −4113; 95% CI, −4862 to −3364), and similar results were found for WHR (β coefficient −4272; 95% CI, −5280 to −3264) and fat mass (β coefficient −4,590; 95% CI, −5,386 to −3,793). 

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Compared with lean adults, individuals with obesity (BMI ≥30 kg/m2) and central obesity (WHR >0.85 for women, >0.90 for men) had the lowest gray matter volume (β = −4496; 95% CI, −8820 to −172; P =.04). In addition, obesity was associated with lower caudate (only WHR), putamen (only BMI and total fat mass), pallidum, and nucleus accumbens volumes (P <.001), according to findings from hypothesis-free testing with a Bonferroni correction.

Limitations of the analysis include its observational nature as well as the reliance on self-reports to identify people with chronic disease.

“It is unclear whether structural brain abnormalities drive obesity or whether obesity induces changes in gray matter volume that play a mechanistic role in future risk of neurodegeneration,” the researchers explained.

Reference

Hamer M, Batty GD. Association of body mass index and waist-to-hip ratio with brain structure: UK Biobank study. Neurology. 2019;92(6):e594-e600.