Introduction

Vitamin D (vit D) deficiency is considered as a health problem worldwide. Nowadays, vit D deficiency has involved more than half of people worldwide.[1] The prevalence of vit D deficiency in Tehran and Isfahan was estimated about 81/3% and 70/16%, respectively.[2] vit D plays an important role in calcium metabolism, maintenance of the skeleton, control of cell proliferation and differentiation, and immunity.[3] Recently, it has been shown that vit D deficiency has a strong relationship with increased risk of type 2 diabetes, cardiovascular disease (CVD) as well as CVD risk factors such as hypertension and obesity.[4] Obesity was recognized as an epidemic of the 21st century by World Health Organization (WHO)[5] and it is a serious health problem worldwide.[5,6] Since 19th century, the prevalence of obesity has increased along with changes in diets and lifestyle factors.[7] WHO estimated that at least 300 million adults are obese and more than 1 billion are overweight worldwide.[7,8] It is proved that 3.4 million of obese and overweight people are died due to obesity and comorbidities including hypertension, type 2 diabetes, stroke, CVD, some type of cancer such as prostate, breast, ovary, cervix, colon, and gallbladder every year.[5,9] In addition, obesity is related with hypercholesterolemia, osteoarthritis, gastroesophageal reflux, sleep apnea, and kidney chronic disease.[10] Furthermore, this issue becomes a general health problem In Iran. The prevalence of obesity and overweight was 42% in men and 57% in women in 2005, and it was anticipated to reach 54% and 74% among men and women, respectively by 2015.[11] A study In Iran showed that obesity in women are more than twice than men.[12] In a performed study in Isfahan, all women over than 65 years had abdominal obesity.[13] Lifestyle modification such as proper exercise is the best and cheapest way for decreasing the obesity. In addition, diet plays a key role in weight loss programs.[7] Today’s attention toward the role of vit D in chronic diseases such as obesity is increasing. Based on several studies, obese and overweight people mostly have a lower levels of vit D than those who have less body fat.[14] Some studies suggested that obesity increased risk of vit D deficiency[15] whereas other studies shown that insufficient levels of vit D could increase the risk of type 2 diabetes, CVD, and risks such as hypertension and obesity.[16] A previous study has shown that vit D deficiency is more common in obese people.

It was seen that there is an inverse association among vit D with body mass index (BMI) and waist circumference (WC).[4,17,18,19,20] However, conflicting results had been seen such as a study among Iranian individuals aged 20-64 years with BMI of 24.2 ± 3.8 (57% female) which has not shown significant association between serum levels of vit D and BMI.[4] In this study, we tried to perform a comprehensive assessment about the effects of vit D supplementation and body weight as well as other anthropometric measurements, BP, lipid profile, glycemic indices, and C-reactive protein (CRP) among Iranian women. Therefore, our main purpose was to examine the effect of vit D on weight loss in obese and overweight women aged 20-40 years in Isfahan.