|Year : 2015 | Volume
| Issue : 2 | Page : 83-87
Effects of vitamin D supplementation on anthropometric indices in vitamin D-deficient obese Saudi females; a randomized controlled trial
Noura Saad Al-Mulhim, Tharwat Gamal Eldin, Rabia Latif, Lubna Ibrahim Al-Asoom, Ahmed Al-Sunni
Department of Physiology, College of Medicine, University of Dammam, Dammam, Saudi Arabia
|Date of Web Publication||16-Jun-2015|
Department of Physiology, College of Medicine, University of Dammam, Dammam
Source of Support: Deanship of Scientific Research, University of Dammam, Saudi Arabia, Conflict of Interest: None
Background and Aim: Vitamin D (VD) is well-known for its traditional but essential role in calcium homeostasis and bone metabolism. However, the evidence suggests that VD endocrine system is linked to obesity as well. In adults, an inverse relationship has been reported between adiposity and circulating VD. The purpose of present study, therefore, was to investigate the effect of VD supplementation on anthropometric indices in a population of VD deficient obese Saudi females. Materials and Methods: It was a randomised controlled trial (RCT) for which 30 vitamin D deficient obese female students were recruited from our university and divided as: 1) Vitamin D group (oral 50,000 IU cholecalciferol/week for 8 weeks and 2) Placebo group (sterile drops). Weight, height, waist and hip circumference were recorded. Body mass index (BMI) and waist-hip ratio were calculated at the beginning and in the end. Statistical Analysis: Two sample t-test, paired t-test and Pearson correlation. Results: After treatment with 50,000 IU of VD weekly for 8 weeks, a significant decrease in waist circumference was observed in VD group compared to their pre-treatment measurement (100.8 ± 8.4 vs 96.7 ± 10.4; P = 0.04), although there was no significant change in any other variables (P > 0.05). No significant differences were observed among the groups in the beginning or in the end. Serum VD levels were not significantly related to any of the anthropometric variables at baseline in both groups. Conclusions: Correction of 25 (OH) D concentrations led to significant reduction in waist circumference in VD deficient young Saudi obese female students without affecting other anthropometric indices.
Keywords: Obesity, randomised controlled trial, Vitamin D, waist circumference
|How to cite this article:|
Al-Mulhim NS, Eldin TG, Latif R, Al-Asoom LI, Al-Sunni A. Effects of vitamin D supplementation on anthropometric indices in vitamin D-deficient obese Saudi females; a randomized controlled trial. Saudi J Health Sci 2015;4:83-7
|How to cite this URL:|
Al-Mulhim NS, Eldin TG, Latif R, Al-Asoom LI, Al-Sunni A. Effects of vitamin D supplementation on anthropometric indices in vitamin D-deficient obese Saudi females; a randomized controlled trial. Saudi J Health Sci [serial online] 2015 [cited 2023 Mar 22];4:83-7. Available from: https://www.saudijhealthsci.org/text.asp?2015/4/2/83/157863
| Introduction|| |
Obesity is increasing at an alarming rate in Saudi Arabia. In a community-based national epidemiological health survey, the prevalence of overweight and obesity were found to be 36.9 and 35.5% respectively. Females were significantly more obese than males (P < 0.0001).  Another survey conducted in eastern province only, the overall prevalence of obesity and overweight was found to be 43.8 and 35.1% respectively.  Another study found that the Eastern province has the highest rates of obesity.  Most recently, the World Health Organisation (WHO) global status reported a high prevalence of obesity in Saudi Arabia, around 33% of total population where sex variation was obvious with more prevalence in females (around 39.1%) than in males (28.65%).  Overall, these studies outline that obesity is highly common in Saudi populations and more common in female adults, which highlights the need for a well-structured obesity prevention programmes.
Vitamin D (VD) is well-known for its traditional but essential role in calcium homeostasis and bone metabolism. However, the evidence suggests that VD endocrine system is linked to obesity as well. In adults, an inverse relationship has been reported between adiposity and circulating VD ,,,, even after adjustment for age, lifestyle, and Parathyroid Hormone (PTH).  Low levels of VD were common in obesity  and were independently associated with increased Body Mass Index (BMI) and body fat; in both children , and adults.  In addition, overweight and obese females lost more body fat when their VD concentrations were higher.  Many researchers have reported strong negative correlation between 25 (OH) D levels and visceral adipose tissues in obese adolescents  and with visceral and skin adipose tissues in young women.  Several studies have investigated the effect of VD supplementation on body fat of human subjects. , The double-blind, randomised clinical trial by Salehpour et al.,  demonstrated that the consumption of 25 μg/d of cholecalciferol for 12 weeks caused a statistically significant reduction in body fat mass in healthy overweight and obese women. In addition, Salibah et al.,  showed that BMI is inversely associated with increase in serum 25 (OH) D levels in response to VD supplementation.
Collectively, all these studies suggest that, in overweight and obese subjects, VD supplementation may lead to a reduction in body weight and adipose tissues. Though more needs to be learned about the mechanism underpinning VD-induced weight loss, the available data highlight the probable role of VD in favourable decrease of obesity. The purpose of present study, therefore, was to investigate the effect of VD supplementation on anthropometric indices in a population of VD deficient obese females. We hypothesised a greater loss of body weight in VD supplemented group as compared to placebo.
| Material and methods|| |
Approval of this randomised, placebo controlled study was granted by Institution Review Board of our university. All Saudi females studying at health colleges in our university (N = 698) were assessed for eligibility criteria. Our inclusion criteria were 18-23 years old obese (BMI >30 kg/m 2 ), VD deficient (serum 25 (OH) VD <20ng/ml (<50 nmol/l)  Saudi females willing to participate. Students with history of any systemic illness, regularly taking multivitamins especially VD, Pregnancy or lactation were excluded from the study. Out of 46 students meeting the inclusion criteria, 10 students withdrew consent for personal reasons and four students were excluded due to recent major weight loss. Remaining 32 obese female students were screened for VD deficiency out of which two students were found to be VD sufficient; hence excluded from the study.
Study participants were randomly assigned into VD group (received 50,000 IU/wk of vitamin D3 drops) or placebo group (received normal saline drops/wk) for 8 weeks duration. A block randomisation procedure with serial entry in blocks was used.  Four participants were included in each block, ensuring that within each block two participants were allocated to VD group and two were allocated to placebo group. All participants from both groups received their dose under supervision in the Physiology department laboratory, college of medicine of our university. Participants were advised to maintain their usual diets and avoid taking VD supplementation on their own throughout the study period.
VD status was assessed by measuring serum 25 (OH) VD level by Enzyme-linked Immunosorbent Assay (ELISA) before randomisation to involve only VD deficient subjects. Anthropometric variables were obtained at the beginning and in the end of the study. Subjects were asked to void their bladders before measurement and to wear light clothes. Height was measured barefoot using a stadiometer to the nearest 0.1 cm and weight was obtained to the nearest 0.1 kg using a digital scale. BMI was calculated as weight (kg)/height (m) 2 . Waist circumference was measured using plastic tape to the nearest 0.1 cm.
The data were analyzed using Microsoft Office Excel and the Statistical Package of Social Science (SPSS-IBM) version 20. Data are presented as Means ± Standard Deviation (SD). Differences between groups were assessed by a two-sample t-test. Paired sample t-test was used to compare changes within each group (Pre and Post treatment) of all variables. Pearson correlation was used to find the relationship between serum VD and various anthropometric variables at baseline in both groups. A 'P' < 0.05 was taken as statistically significant.
| Results|| |
Baseline characteristics of subjects are shown in [Table 1]. No significant difference was observed in baseline characteristics between groups. The paired t-test results demonstrated that, the mean values of body weight and body mass index were insignificantly increased after treatment with placebo and insignificantly decreased after VD treatment. Interestingly, the mean values of waist circumference was found to be significantly decreased after treatment within VD group with P = 0.04 [Table 2]. However, no significant difference was found within the placebo group.
|Table 2: Anthropometric indices before and after treatment with vitamin D or placebo in both groups|
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The mean values of hip circumference and waist to hip ratio after treatment was similar to baseline, with no significant differences were found within the groups.
The comparison of the post- treatment results of body weight, BMI, waist circumference, hip circumference and waist to hip ratio between placebo group and VD group revealed no significant differences between the groups [Table 3].
|Table 3: Comparison of the post-treatment anthropometric results between the placebo and vitamin D group|
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Serum VD levels were not significantly related to any of the anthropometric variables at baseline in both groups [Table 4].
|Table 4: Correlations between 25 (OH) D and anthropometrics indices at baseline for vitamin D group and placebo group|
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| Discussion|| |
In this randomised placebo controlled study, VD supplementation for 8 weeks in obese VD deficient Saudi females demonstrated a significant reduction in waist circumference compared to the pre-treatment value in the treated group only. However no significant effect on other anthropometric measurements was demonstrated in this group. Furthermore no significant differences were shown in all anthropometric data in VD treated group as compared to the placebo.
BMI is merely a ratio of weight in relation to height. It is not a direct measurement of body fat, and notably this ratio offers no information about distribution of body fat. Contrarily, the measurement of waist circumference provides information about fat distribution. Waist circumference is considered a comparatively good indicator of visceral fat accumulation.  Hence our results indirectly indicate a significant decrease in visceral adipose tissue by VD supplementation.
Our results are in concordance with a recent randomised controlled trial (RCT) in which VD supplementation has resulted in a significant loss of visceral fat without affecting lean body mass or BMI.  Research conducted by Rosenblum et al., also support our results who suggested that VD supplementation contributes to a beneficial reduction of visceral adipose tissues in overweight and obese adults.  In another RCT, Major et al., also documented visceral fat loss independent of energy restriction induced by VD supplementation; suggesting a beneficial effect of VD intake on weight management.  Our finding is consistent with those of Mason et al.,  who found that women who received 2000 IU/d oral vitamin D3 for 12 months and became replete [25 (OH) D ≥ 32ng/ml] had a greater improvement in waist circumference compared with women who did not become replete despite vitamin D3 supplementation (-6.6 cm compared with -−2.5 cm; P = 0.02).
On the other hand, our finding differs from that of Gallagher JC et al.,  who showed that after one-year treatment with VD (400-4800 IU/d) in VD deficient obese, there was no significant effect of VD on body fat mass (measured by Dual energy X-ray absorptiometry) in VD deficient subjects. However that study may not directly comparable with ours due to the differences in dosage of VD (4800 IU/day VS 50,000 IU/week), supplementation period (1 year vs 8 weeks), ages of the subjects (57-90 vs 18-25 years old), ethnicity (Caucasians vs Arab), and methodology used to measure body fat (dual-energy X-ray absorptiometry; a more precise and accurate method vs WC; a crude method). Similarly the study conducted by Belecnchia et al.,  showed that vitamin D3 supplementation (4000 IU/d) for 6 months had no effect on anthropometric variables including waist circumference in obese adolescent patients. This inconsistency in results can be explained by differences in VD dosage used (4000 IU/day vs 50000 IU/week).
The underlying mechanism of VD-induced reduction in WC and loss of adipose tissue can be explained by the fact that the lack of VD leads to secondary hyperparathyroidism,  which may promote an increase in free intracellular calcium into adipocytes,  and, thereby enhance lipogenesis by impeding the catecholamine-induced lipolysis, , and also by promoting expression of fatty acid synthase.  This causes fat accumulation leading to obesity. Restoration of VD to normal levels may reverse the whole process and may lead to fat loss.
Our data show no change in BMI after 8-week VD supplementation period. This is in agreement with four interventional studies demonstrated that VD supplementation has no effect on body weight. For example, the 12-month, randomised, double-blind clinical trial conducted by Sneve et al.,  revealed that significant weight reduction in overweight and obese subjects is unlikely to occur with supplementation of 20,000 IU of cholecalciferol along with 500 mg calcium twice a week. Furthermore, a double-blind, randomised study for one year found that no significant differences in body weight and BMI was observed between a VD group after supplementation of 3332 IU/d of vitamin D 3 and a placebo group.  Another randomised, placebo-controlled study investigated the association between anthropometric measures of adiposity and serum 25 (OH) D after a supplementation of 15 μg/d cholecalciferol in healthy young and old Irish adults. It was found that BMI in younger adults was insignificantly associated with the change in 25 (OH) D after supplementation. 
| Conclusion|| |
Correction of 25 (OH) D concentrations lead to significant reduction in waist circumference in VD deficient young Saudi obese female students without affecting other anthropometric indices.
The strengths of our study include the use of a RCT design and assessment of study compliance through weekly follow-ups. Likewise, expected increase in VD concentrations in all members of the VD supplemented group also support good participant compliance.
Several limitations of the study should be noted which include the small sample size and the short duration of the study. Our trial lasted for only 8 weeks, and a longer study may have resulted in favourable improvements in other anthropometric indexes as well. We recruited subjects with BMI >30 kg/m 2 and, hence, our results may not be applicable to a leaner population. The study was not blinded at all. Moreover, the recruitment of primarily Saudi females limited the ability to generalize our findings to males or other ethnic groups. Last but not the least; the study is limited by the lack of dietary records which might have possibly influenced results.
Clinical implication of our study
Waist circumference measurement is increasingly recognised as being a more important tool than simple BMI measurement because determining an individual's waist circumference measurement gives a vague idea about the amount of visceral fat. Visceral fat in particular appears to be associated with insulin resistance which leads to type 2 diabetes and adverse lipid profiles which in turn predispose to cardiovascular disease. If VD supplementation reduces waist circumference or in another words, visceral fat, then it may decrease an individual's health risks associated with overweight and obesity.
| Acknowledgement|| |
The authors acknowledge the financial support given by Deanship of Scientific Research, University of Dammam, through Grant number P2012011 for conducting this research.
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[Table 1], [Table 2], [Table 3], [Table 4]