Low 25-hydroxyvitamin D concentrations in obese women: Their clinical significance and relationship with anthropometric and body composition variables
N. Vilarrasa1, J. Maravall1, A. Estepa1, R. Sánchez2, C. Masdevall2, M.A. Navarro3, P. Alía3, J. Soler1, and J.M. Gómez1
1Endocrinology and Diabetes Unit; 2Department of Bariatric Surgery; 3Department of Biochemistry, Bellvitge Universitary Hospital, Barcelona, Spain

Obesity is associated with low concentrations of 25-hydroxyvitamin D [25(OH) D]. However, conflicting results have been found regarding the relationship of 25(OH) D with anthropometric and adiposity parameters. The aim of our study was to analyze the association between 25(OH) D and body fat (BF) in a homogeneous cohort of non-obese, obese, and morbidly obese Caucasian women. The study was performed in L´Hospitalet de Llobregat, a city adjacent to Barcelona with a latitude of 41 degrees, 22 minutes, and 5 seconds north. Materials and Methods: Plasma concentrations of 25(OH) D were determined and body composition was evaluated by bioelectrical impedance in a group of 43 women with morbid obesity, 28 non-morbidly obese, and 50 non-obese women matched for age. Results: Morbidly obese women showed lower 25(OH) D concentrations compared to non-morbidly and non-obese women (37.9±16 vs 40.2±13 vs 56.7±21 nmol/l, p=0.001). Fifty-one percent of morbidly obese women had vitamin D deficiency [25(OH) D<38 nmol/l] compared to 22% of non-obese patients, (p=0.004). In the bivariate correlation analysis 25(OH) D was inversely associated with weight (r=-0.41, p=0.001), body mass index (BMI) (r=-0.432, p=0.001), waist to hip ratio (WHR)(r=-0.40, p=0.001), BF (r=-0.53, p=0001), fat mass (r=-0.44, p=0.0001), fat-free mass (r=-0.35, p=0.001). In the multivariate general linear model analysis, 25(OH) D was associated with season of examination (p=0.001) and was negatively associated with BF (beta=-0.75, p=0.001), after adjusting for age, BMI, and WHR. Conclusions: 25(OH) D concentrations are associated with body composition variables especially by BF, independently of seasonal variability. Therefore, body adiposity should be considered when assessing vitamin D requirements in obese patients. (J. Endocrinol. Invest. 30: 653-658, 2007) ©2007, Editrice Kurtis

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