Effect of adipose tissue volume loss on circulating 25-hydroxyvitamin D levels: results from a 1-year lifestyle intervention in viscerally obese men

BACKGROUND/OBJECTIVES: Although weight loss has been associated with changes in circulating 25-hydroxyvitamin D (25(OH) D) levels, the quantification of the increase in 25(OH) D levels as a function of adipose tissue volume loss precisely assessed by imaging has not been reported before. The objective of this substudy was to describe the effects of a 1-year lifestyle intervention on plasma 25(OH) D levels. The relationships between changes in 25(OH) D levels and changes in adiposity volume (total and by adipose tissue compartment) were studied. SUBJECTS/METHODS: This intervention study was performed between 2004 and 2006 and participants were recruited from the general community. Sedentary, abdominally obese and dyslipidemic men (n = 103) were involved in a 1-year lifestyle modification program. Subjects were individually counseled by a kinesiologist and a nutritionist once every 2 weeks during the first 4 months with subsequent monthly visits in order to elicit a 500-kcal daily energy deficit and to increase physical activity/exercise habits. Body weight, body composition and fat distribution were assessed by dual-energy X-ray absorptiometry and computed tomography, whereas the 25(OH) D levels were measured with an automated assay. RESULTS: The 1-year intervention resulted in a 26% increase in circulating 25(OH) D (from 48 +/- 2 nmol l(-1) or 19 +/- 0.8 ng ml(-1) (+/- s.e.m.) to 58 +/- 2 nmol l(-1) or 23 +/- 0.8 ng ml-1, P < 0.0001) along with a 26% decrease in visceral adiposity volume (from 1947 +/- 458 to 1459 +/- 532 cm(3)). One-year increases in 25(OH) D levels correlated inversely with changes in all adiposity indices, especially Delta visceral (r = -0.36, P < 0.0005) and Delta total abdominal (r = -0.37, P < 0.0005) adipose tissue volumes. CONCLUSIONS: These results indicate that there is a linear increase in circulating 25(OH) D levels as a function of adiposity volume loss, and therefore suggest a role of adiposity reduction in the management of obesity-associated vitamin D insufficiency.