Xiao-Mei Mai of Norwegian University of Science and Technology and colleagues evaluated data from 2,460 men and women aged 19 to 55 who participated in the second and third surveys of the Nord-Trøndelag Health Study, conducted between 1995 to 1997 and 2006 to 2008. Serum 25-hydroxyvitamin D levels and anthropometric measurements were obtained upon enrollment and at follow up.
Upon enrollment, 12 percent of the subjects were classified as obese [defined as having a body mass index (BMI) of 30 or more] and 15 percent were classified as obese after 11 years of follow-up. Having a serum vitamin D level below 50 nmol/L was associated with a four times greater adjusted risk of obesity than that experienced by subject whose levels were 75 nmol/L or higher at the beginning of the study, and with a 1.73 times greater risk of developing obesity over follow-up. Similar results were observed when waist circumference was used to classify obesity, indicating an association with central adiposity.
“Our study is one of the few prospective cohort studies to have investigated the possible effect of low vitamin D status on change in adiposity and development of obesity,” the authors write. “We found a consistent inverse association between baseline 25-hydroxyvitamin D levels and incident obesity defined by either BMI or waist circumference after 11 years of follow-up, and this inverse association was not modified by season of blood sample collection.”
They recommend large prospective studies to further investigate the relationship between low vitamin D levels and the development of obesity.