MetS is a medical condition associated with metabolic disorders. Different cut-offs have been used to define MetS, with 1) the World Health Organization , 2) the European Group for the Study of Insulin Resistance , 3) the National Cholesterol Education Program-Third Adult Treatment Panel , 4) the American Association of Clinical Endocrinology  and 5) the International Diabetes Federation  cut-offs being the most commonly used. The existence of several criteria has created confusion when the prevalence of MetS is compared within or among populations . The IDF standard has been described as the most appropriate and the most convenient for screening MetS in children and adolescents  since it combines international diagnostic criteria and takes into consideration the ethnic-specific limits of waist circumference and central obesity . In the UAE, the IDF standard had a sensitivity superior to those of the NCEP and ATPIII for the early diagnosis of MetS among Emirati [18, 30].
The prevalence of MetS in the region has been extensively reported among adults but has been less abundantly studied among young populations. In the UAE, the percentages have been found to vary between 29 and 40.5% [18, 19, 30] in adults, with lower but significantly high proportions also reported in children and adolescents living in the UAE [31,32,33]. The observed variations in numbers and percentages have been attributed to several factors, including the region selected, the reference criteria used for screening, and other important factors.
In our study, the prevalence of MetS, according to the IDF criteria, among a representative random sample of adolescents aged 10 to 15.9 years old who were attending public schools in Dubai was 3.7%. This estimate is considerably lower than those presented in previously reported results in the UAE and countries in the region, where numbers have varied significantly, mainly due to a lack of consensus on the criteria used to define MetS. Studies that have assessed the prevalence of MetS using different diagnostic standards have consistently produced different outcomes [16, 34, 35], with values sometimes differing more than two-fold .
Interestingly, Khashayar et al.  found a prevalence of 2.4% among a representative sample (5738 students) living in 23 provinces in Iran. It is worth noting that the same screening methods were used for the assessments performed in Iran, and this might have contributed to the similarities in our findings. In Egypt , when the NCEP was used as a reference, 7.4% of a representative sample of 4250 adolescents aged 10 to 18 years old were diagnosed with MetS, and similar results (9.1 and 9.4%) were found among adolescents living in Saudi Arabia and Kuwait (respectively) when modified ATP III criteria were used [34, 38].
Although the overall prevalence of MetS is low, its risk factors, such as abdominal obesity, were widespread among our young population, and they dominated among males. This was also demonstrated in the prevalence of MetS. Similar to other studies performed in the region [31, 36, 39,40,41,42], the prevalence of MetS was higher among boys than girls (3.9% of boys versus 3.5% of girls). This difference could be attributable to differences in sex hormones, such as testosterone and sex hormone-binding globulin (SHBG), which are strongly expressed during puberty .
According to BMI z-score data, almost half of the sample population was overweight or obese, and 15% of the sample had a high waist circumference. Approximately 51% of the adolescents had at least one component of MetS (low HDL levels, high blood pressure, high fasting glucose, high triglycerides or abdominal obesity), and the prevalence of these components was higher among children with obesity, followed by those with overweight and then those with normal weight. This is a cause of great concern since obesity and metabolic disturbances can remain until adulthood, increasing the risk of diseases later in life [4, 5]. The rate of MetS (as well as all of its biochemical markers) was significantly higher in obese people (16%) than in overweight individuals (2%). This finding is strongly supported in the literature; for instance, among 263 Lebanese adolescents, MetS was identified in approximately 21% of obese, 4% of overweight, and 1% of normal weight subjects .
HDL (followed by high blood pressure) was found to be the predominant risk factor among adolescents living in Dubai, as was previously reported in different studies performed in the UAE  and other countries in the region [41, 44]. If MetS did not account for HDL levels, our data would have resulted in a prevalence of 0.8% of MetS (only 5 students). This assumption, in addition to the results of the logistic regression, demonstrates the impact of low HDL levels on health.
The presence of genetic determinants for MetS has been suggested, and these could make certain populations more vulnerable to developing chronic abnormalities. Studies that investigate genetic susceptibility to having low HDL have identified several predisposing variants among Arabs . This hypothesis was supported in a recent study that identified many predisposing variants at the genome level that affected the expression of cholesteryl ester transfer protein (CETP) and LIM- and cysteine-rich domain 1 (LMCD1) genes, resulting in low HDL levels in ethnic Arabs . These results were strongly supported by other papers that assessed the lipid profile of all age groups in the region. Bayoumi et al.  mentioned that in Omani people, weight and HDL levels were highly determined by genetics, while other risk factors were triggered by environmental influences. Additionally, approximately 87% of Saudi children and adolescents aged between 10 and 18 years old had low HDL levels , and this was classified as the most dominant risk factor among the population. Very similar results were also found among Saudi adults . Since low HDL levels are a risk factor of CVDs, this theory could explain why the eastern Mediterranean region , which mostly includes Arab countries , has the highest prevalence of deaths attributed to CVD.
Despite the fact that there is evidence showing that a genetic component is associated with the low HDL levels observed among Arab populations, it is crucial to look at the picture from different angles. There are several types of HDL cholesterol, and they have different risk levels. For instance, when apolipoprotein A-I Milano (ApoA-1M) is the predominant HDL particle, the pro-atherogenic effect of low HDL levels is abated . This was first discovered in Italy, a country that neighbours several Arab countries and contains populations that could share the same genetic inheritance. This hypothesis needs substantial investigation of HDL apolipoproteins among our populations.
Finally, it is crucial to define a gold standard method to determine HDL levels. A study published by Mehairi et al.  recently assessed the prevalence of MetS in 1018 adolescents aged 12 to 18 years old living in Al Ain, UAE, and found that the prevalence was 13% when the IDF reference was used.
If we dig deeper into the baseline biochemical characteristics of the sample population, the large variance can be explained. If we exclude blood pressure and waist circumference measurements, which rely on the skills of the data collectors, the differences in biochemical parameters among both populations do not exceed 13% (no differences for LDL or total cholesterol values, while the difference for glucose was approximately 4% and that of triglycerides was 13%) except for HDL values, which varied by 23%. The biochemical blood analyses performed in the two studies took place in different laboratories that used different methods to analyse HDL levels. It is important to note that there is no consensus regarding the analysis of HDL, and differences in the methods used to obtain measurements could result in large variations in results. The higher HDL values reported in the paper by Mehairi et al.  could have resulted in a lower prevalence of MetS since low HDL levels were found to be the most predominant risk factor.
Our study has a number of limitations. First, our sample population was drawn from only 1 Emirate: Dubai. The UAE federation consists of 7 Emirates, and although the Emirati populations across the UAE have similar dietary habits, we could not confirm how representative our sample population is of the country as a whole. Second, our sample was drawn only from public/government schools, which mainly consist of Emirati students. However, a small percentage of Emiratis also attend private schools. Hence, the inclusion of private schools may have produced different results. Finally, no waist circumference cut-off values were available for our population; hence, we used international cut-off points.