We evaluated in this study the lipid profile, prevalence of VD deficiency and the effect of VD supplementation among CCS, and the overall effects of the 6-month VD supplementation on their VD levels, weight status, and lipid profiles.
Lipid profile and VD effect
This study found significantly higher levels of TC and LDL-C among obese patients which reduced significantly after VD treatment/supplementation. Other studies on obese children, reported associations between low 25OH-VD levels and unfavorable lipid profiles . Censani et al.  reported that VDD patients (25OH-VD < 20 ng/mL) had significantly higher TC, TG, and LDL-C levels compared with patients with higher VD (25OH-VD = 20 ng/mL). Sriram et al.  and Rusconi et al.  showed an inverse correlation between 25OH-VD levels and TC/LDL-C levels.
Aypak et al.  found a higher LDL-C and TG, and lower HDL-C in obese children compared to lean children. Conversely, Rajakumar et al.  and Delvin et al.  found no differences in most lipid parameters (TC, LDL-C, TG) between subjects with sufficient/deficient 25OH-VD. Although they did not give an explanation for this, however, Rajakumar et al.  reported a positive correlation between plasma 25(OH)D and HDL cholesterol (a favorable lipid biomarker) in both black and white children. Furthermore, they found that vitamin D deficiency was associated with higher adiposity measures (visceral adipose tissue in whites and greater subcutaneous adipose tissue in blacks and explained this finding by ethnic differences between African–American and Caucasian races).
Obese patients had a significantly lower 25OH-VD and higher VDD percentage (88.2%) compared to (50%) in non-obese patients.
Few studies have reported low VD in obese children. Olson et al.  evaluated 6-16 years olds of which 411 were obese and 87 non-overweight (control group), and reported VDD as being significantly more prevalent in obese children. Another study, Rajakumar et al.  studied VD status in African-American children finding VDD being detected in 57% (12/21) obese patients versus 40% (8/20) non-obese patients as a baseline. After a trial run of VD treatment for 1 month: VDD was still persistent in 24% (5/21) obese patients and 11% (2/18) non-obese patients.
Low VD levels among obese subjects were explained with reduced bioavailability because of storage of VD (fat-soluble vitamin) in larger fat compartment tissues (dilutional) . Also, sedentary lifestyles of obese individuals and reduced outdoor activities with less sunlight exposure which is essential for VD production [14, 15]. It may be also because, food imbalance favoring energy-dense foods by obese children at the expense of foods rich in vitamins and minerals (vegetables, fruits) as well as meat or fish, which decrease availability of VD intake . It may be also as a result of compensatory hyperparathyroidism has been observed in obese adults with low 25OH-VD levels [4, 5].
VD and PTH effects on adiposity
This study reports no change to body weight and BMI after VD treatment/supplementation of obese patients. As weight reduction requires integrated strategies such as implementing strict dietary controls, involvement in fitness, and physical exercise. This is consistent with previous researches confirming no reduction of body weight or BMI in obese adolescent children or adults after VD treatment for 3 up to 12 months [17, 18]. High levels of PTH, which persisted among obese VDD groups even after VD supplementation, may be an indication of more need for VD to be given to those patients. Similar to our study, Amini et al.  and Rusconi et al.  reported that 25OH-VD deficiency in obese children was also associated with higher levels of PTH.
VD treatment for obese children
In our study, VD supplementation trials were less successful in increasing 25OH-VD in all obese patients, possibly suggesting the requirement for higher doses or more frequent courses of VD treatment/supplementations in obese children. Previous studies support and suggest the need for higher doses to be administered to obese children as their bioavailability evaluations, after oral VD at 50,000 units, were found to be less effective . Harel et al.  in their study, evaluated a high dose VD treatment trial administered to VDD obese adolescents (25OH-VD < 20 ng/ml) at 50,000 units per week for 6-8 weeks, and for VDI (25OH-VD, 20-30 ng/mL) at 800 units per day for 3 months, and reported a significant increase in 25OH-VD after the initial course of VD treatment in only 28% of the participants.
Limitation of the study
The small sample sizes of the study, being conducted in a single-center, retrospective nature of the study, non-randomization of patients, were some limitations of this study. There was also a difficulty in evaluating the exact food consumption and physical activity of patients (which certainly would affect VD and weight status of our studied patient) because of recall bias and non-cooperation of many parents/patients.