This study was conducted to develop gender and age specific cut-off points of BF% for healthy Qatari adults to determine their risk of having metabolic syndrome. These cut-off points of BF% have been created based on DEXA, anthropometric and biochemical data that have been collected from the study participants.
Body fat percentage is a better indicator of metabolic risk factors than body mass index [12]. The ability of BMI to diagnose obesity and risk of disease remains questionable [13]. The accuracy of BMI is limited due to the inability to measure body fat percentage directly from total body fat, total body lean mass, and total bone mass [14]. Different ethnic groups showed different results based on age and gender [15]. Therefore, additional cross-ethnic studies are required, as body fat percentage and BMI relations are affected by ethnicity, age and gender [16].
A study carried out on middle-aged Japanese men showed a link between BF% and CVD risks, such as diabetes mellitus, dyslipidaemia and hypertension [17]. Li et al. (2012) revealed that there is a relationship between BF%, type 2 diabetes, and metabolic syndrome. They used BF% from the Shanghai Diabetes Studies, which were 25% for men and 35% for women [14].
In our study, BF % cut-off values that were associated with metabolic syndrome for Qatari adults aged < 40 years old and ≥ 40 years old were 35.1 and 45.1% for men, and 34.8 and 46.3% for women. The result obtained from BF% showed a clearer link to metabolic syndrome risk for women, compared to men. This could be due to higher fat mass and lower lean body mass in women than men. Furthermore, women aged < 40 years had higher BF% area under the curves (AUC) for CVD risk factors than women age > 40 years. This high AUC of women < 40 years old means that the results are diagnostic for a large number of women in this age range, thus giving higher predictability for metabolic risk and allowing early intervention to be initiated.
One of many similar studies is a study conducted by Li et al. in 2017 aimed at determining cut-off values of BF% to estimate the risk of cardiovascular disease [14]. This was a cross-sectional study which included 3221 Chinese adults from two different ethnicities (2308 Han and 913 Mongolian). The study included 898 Han men and 355 Mongolian men, and 1410 Han women and 558 Mongolian women, with an age range of 20–80 years old. The BF% cut-off points were measured using bioelectrical impedance. In the Mongolian population, men had body fat cut-off points of 25% and women had cut-off points of 35%. The results were similar for the Han population [14]. Other studies in Korea supported the fact that BF% is a strong indicator for cardio-metabolic risk [18]. Kim et al. stated that BF% cut-off points in Korean populations are 21 and 37% for men and women, respectively [18]. Moreover, another study has established individualised BF% cut-off values for the Asian-Indian people, reporting that men have a cut-off point of 24.5%, while that of women is 38% [19].
The present study’s results of trunk fat indicated that the specificity of trunk fat to predict metabolic risk was higher in males aged < 40 (84.7%) than females aged < 40 (68.2%); whereas the sensitivity was higher for women (86.2) than in men (67.6) at age < 40 years.
One of the studies related to visceral fats is a study that involved 278 girls and 302 boys between the age of 3–19 years old [20]. Analysis of trunk fat was accomplished by DEXA. Specificity and sensitivity of trunk fat in boys were 92 and 87%, and in girls were 94 and 89% [20]. Researchers have stated that the difference between boys and girls might be attributed to differences in body construction (apple shape, gynoid shape), in addition to the specific skeletal structure of each gender.
Snijder and co-workers (2004) conducted a study to investigate the association between trunk fat and blood glucose levels. They revealed that there is a strong correlation between trunk fat and metabolic syndromes, such as diabetes [21]. Meanwhile, Taylor et al., (2012) have reported that abdominal adiposity increases the risk of diabetes and cardiovascular disease based on their study of the Indian population [22]. Trunk fat in this population was measured using DEXA that measured fat in the abdominal area, such as the liver, subcutaneous fat and other tissues as well [22].
Our results revealed the visceral fat cut-off points associated with metabolic risks were slightly higher in men in comparison to those of women in both age ranges, with 1.2 kg visceral fat cut-off value in men and 0.8 kg cut-off value for women under the age of 40. A result, 2.0 kg of visceral fat has been indicated as the borderline for men ≥40 to get a metabolic disease, while the borderline for women ≥40 is 1.0 kg of visceral fat.
One of the studies related to visceral fat is a cross-sectional study conducted by Amato et al., (2011) among Caucasian Sicilian subjects. The sample size was 1764 primary care (PC) patients, of whom 585 were men and 1179 were women, aged between 16 and 99 years old [23]. The researchers have indicated a strong relationship between the visceral adiposity index (VAI) and metabolic risk factors. In primary care patients < 30 years, 30–42 years, 42–52 years, 52–66 years, > 66 years, VAI cut off points were 2.52, 2.23, 1.92, 1.93, and 2, respectively [23].
Trunk and visceral fat percentages – unlike the trunk and visceral fat mass- may provide information about the visceral fat and trunk fat in relation to the total body mass. However, our analysis did not show a privilege of using percentage of fat over using mass of fat (specificity and sensitivity were comparable).