At the same time, vitamin D deficiency is associated with a decrease in immune cell proliferation as well as synthesis of cytokines, including IL1, IL2, IL6 and IL12, TNF-α and IFN-γ. These cytokines, which are upregulated in patients with obesity and metabolic syndrome, decrease the serum concentrations of vitamin D. Thus, it has been presumed that in overweight patients, as the amount of visceral adipose tissue increases, the kidnapping of vitamin D by adipose tissue increases. Secondarily, it is proposed that vitamin D deficiency or insufficiency is responsible for insulin resistance and thereby promotes metabolic syndrome . Vitamin D deficiency has been associated with increased airway hyperresponsiveness, decreased lung function, reduced asthma control, and resistance to steroids . A recently conducted study of treated asthmatic children showed that 84.2% of children with asthma had low levels of vitamin D. In that study, overweight was an important risk factor for vitamin D deficiency and insufficiency . Another study found that vitamin D deficiency is associated with an increased risk of severe asthma in asthmatic adults (odds ratio [OR], 5.04; 95% confidence interval [CI]: 1.23 to 20.72; p = 0.02) and that high levels of vitamin D are related to a lower risk of hospitalization or emergency department visitation in the past year (OR, 0.90; 95% CI, 0.84 to 0.98; p = 0.04) . Obesity and overweight have also been associated with increased residual capacity and increased risk of asthma. It has been observed that children with asthma are at an increased risk of exacerbations as well as uncontrolled asthma [51, 52]. It has also been shown that there is an association between low vitamin D levels, physical inactivity and high BMI . Alternatively, vitamin D may reduce asthma severity and improve asthma control .