In conclusion , the deficiency of vitamin D is associated with an increased level of BMI in the studies of both diabetic and non-diabetic subjects .
The deficiency of vitamin D is prevalent all over the world .
Studies have shown that vitamin D may play an important role in the development of obesity .
The current study was conducted to quantitatively evaluate the association between serum 25-(OH ) vitamin D levels  and the risk of obesity in both diabetic and non-diabetic subjects .
The serum 25-hydroxyvitamin D response to vitamin D supplementation is related to genetic factors, BMI, and baseline levels.
OBJECTIVE The serum 25-hydroxyvitamin D ( 25(OH)D ) level is not only dependent on vitamin D intake and production in the skin but also dependent on genetic factors . Thus , in large genome-wide association studies , it has been shown that single nucleotide polymorphisms ( SNPs ) in the vitamin D binding protein ( DBP ) , as well as in enzymes related to activation or degradation of vitamin D and its metabolites , are as important for the serum 25(OH)D level as the effect of season . How these SNPs affect the serum 25(OH)D response to vitamin D supplementation is uncertain . DESIGN AND METHODS Data were pooled from three r and omized controlled trials where 40 , 000 IU vitamin D/week was given for 6 months . Serum 25(OH)D was measured before and at the end of the intervention , and the subjects were genotyped for SNPs related to the serum 25(OH)D level . RESULTS Baseline 25(OH)D levels were significantly related to SNPs in the DBP and CYP2R1 genes . Those with SNPs associated with the lowest baseline 25(OH)D levels also had the smallest increase ( delta ) after supplementation . Those with the lowest baseline serum 25(OH)D ( without regard to genotypes ) had the highest increase ( delta ) after supplementation . Subjects with high BMI had lowest baseline 25(OH)D levels and also the smallest increase ( delta ) after supplementation . CONCLUSIONS The serum 25(OH)D response to supplementation depends on genes , baseline level , and BMI . However , whether this is clinical ly important or not depends on the therapeutic window of vitamin D , an issue that is still not settled
In conclusion , the deficiency of vitamin D is associated with an increased level of BMI in the studies of both diabetic and non-diabetic subjects .
The deficiency of vitamin D is prevalent all over the world .
Studies have shown that vitamin D may play an important role in the development of obesity .
The current study was conducted to quantitatively evaluate the association between serum 25-(OH ) vitamin D levels  and the risk of obesity in both diabetic and non-diabetic subjects .