The prevalence of obesity has increased in the last two decades and it is presently the most common and costly nutritional problem. [1–4]. In India, one-third of the population is affected by obesity, according to the National Health and Nutrition Examination Survey. [5]. Despite a known genetic contribution, the increase in obesity prevalence has been largely attributed to lifestyle changes, which means that it is amenable to modification through public health and other interventions. [6]. Vitamin D deficiency is another increasingly prevalent public health concern in developed countries, [7–9]. and there is evidence that vitamin D metabolism, storage, and action both influence and are influenced by adiposity.

Observational studies have reported an increased risk of vitamin D deficiency in those who are obese; however, the underlying explanations and direction of causality are unclear. [10]. Active vitamin D (1,25-dihydroxy vitamin D) may influence the mobilization of free fatty acids from the adipose tissue. [11]. In vitro experiments in rats have also shown that large doses of vitamin D2 lead to increases in energy expenditure due to the uncoupling of oxidative phosphorylation in adipose tissues. [12]. However, randomized controlled trials (RCTs) testing the effect of vitamin D supplementation on weight loss in obese or overweight individuals have provided inconsistent findings. [13–15].

It has also been suggested that obesity could result from an excessive adaptive winter response and that the decline in vitamin D skin synthesis due to reduced sunlight exposure, contributes to the tendency to increase fat mass during the colder periods of the year. [16,17]. However, vitamin D is stored in the adipose tissue and, hence, perhaps the most likely explanation for the association is that the larger storage capacity for vitamin D in obese individuals leads to lower circulating 25-hydroxyvitamin D [25(OH)D] concentrations, a marker for nutritional status. [18]. If lower vitamin D intake/status is causally related to obesity, a genetic variant associated with lower 25(OH) D concentrations should be associated with higher body mass index (BMI) (in proportion to the effect on 25(OH)D). Conversely, if obesity leads to lower vitamin D status, then genetic variants associated with higher BMI should be related to lower 25 (OH)D concentrations.

In our study, we had the youngest patient with 18years and the oldest patient with 78years. In the present study, we had maximum patients in the age group between 41 to 50 years as similar to various other studies. In our study male was 45% with females were 55%.

Table-2: BMI distribution of the study population

Table-3: Distribution of vitamin D levels among the study population

Table-4: Vitamin D levels among the study population

Table-5: Vitamin D Vs BMI (with P-value)

Vitamin D is a fat-soluble vitamin that functions as a pre-hormone and it is naturally present via a few foods or supplements. It can target many specific tissues in the body. Also, it promotes the absorption of calcium from the small intestine and the major biological and phosphate.

Dilution related to the greater volume of distribution has been recently proposed as the most likely explanation for the lower 25 (OH)D concentrations in obese individuals. [24]. In that study, no evidence was found for reduced bioavailability through increased sequestration of vitamin D in the adipose tissue, which had previously been suggested to contribute to the low 25(OH)D concentrations in obesity. [25].

It is also possible that differences in lifestyle could contribute to lower 25(OH)D concentrations in obese compared to normal-weight individuals, although the association between obesity and low 25(OH)D concentrations has been found to only modestly attenuate after adjustment for vitamin D-related lifestyle and dietary factors. [9]. In the present study, serum Vitamin D levels were measured in 100 patients. It was found that 68% of the patients are less than 20ng/dl Vitamin D deficient and 32% had normal levels of more than 20ng/dl. In our study we found statistical significant between BMI and Vitamin D levels in obese patients.

No more study found for similar results. In contrast, associations between BMI and 25(OH)D within levels in the obesity range were consistently linear in studies included in our analyses (unpublished data), hence the observed association between higher BMI and lower 25 (OH) D is likely to be informative in the context of obesity.

In conclusion, the present study demonstrated that the association between BMI and 25(OH)D concentrations in populations from south India can be seen across different age groups and in both men and women. The study also exemplified that higher BMI leads to lower vitamin D status, providing evidence for the role of obesity as a causal risk factor for the development of vitamin D deficiency. The study findings suggest that population-level interventions to reduce obesity would be expected to lead to a reduction in the prevalence of vitamin D deficiency.

The study shows evidence for the role of obesity as a causal risk factor for the development of vitamin D deficiency.