Table 2 displays the characteristics of the study participants by sampling strata. There was a significant over-representation of female students at CoHASS and underrepresentation at CABE and CoE (p-value < 0.001). The proportion of students that consumes alcohol was comparatively low in CoHS (p-value = 0.039). Compared with CANR and CoHASS, a significant proportion of students from CoHS (31.2%), CoE and CoS (18.4% each) never engaged in regular exercise (p-value < 0.001). We observed significant variance in TPBF% measurements compared across the colleges (p-value < 0.001).
Table 2
Characteristics of the study participants by college
Variable | CABE (n = 118, 11.5%) | CANR (n = 81, 7.9%) | CoHASS (n = 150, 14.6%) | CoE (n = 114, 11.1%) | CoHS (n = 407, 39.6%) | CoS (n = 158, 15.4%) | p-value |
Gender | | | | | | | |
Female | 44 (37.3) | 46 (56.8) | 105 (70.0) | 47 (41.2) | 243 (59.7) | 89 (56.3) | < 0.001 |
Male | 74 (62.1) | 35 (43.2) | 45 (30.0) | 67 (58.8) | 164 (40.3) | 69 (43.7) | |
Age (years)* | 20.3 ± 2.0 | 19.9 ± 1.9 | 20.0 ± 1.9 | 20.0 ± 2.0 | 20.1 ± 1.9 | 19.7 ± 1.6 | 0.141 |
< 20 years | 45 (38.1) | 36 (44.4) | 68 (45.3) | 48 (42.1) | 165 (40.5) | 75 (47.5) | 0.581 |
≥ 20 years | 68 (57.6) | 45 (55.6) | 82 (54.7) | 66 (57.9) | 242 (58.5) | 83 (52.5) | |
Year of Study | | | | | | | 0.459 |
1st | 47 (39.8) | 31 (38.3) | 52 (34.7) | 41 (36.0) | 145 (35.6) | 63 (39.9) | |
2nd | 22 (18.6) | 18 (22.2) | 29 (19.3) | 25 (21.9) | 105 (25.8) | 28 (17.7) | |
3rd | 24 (20.3) | 14 (17.3) | 31 (20.7) | 22 (19.3) | 94 (23.1) | 36 (22.8) | |
4th | 25 (21.2) | 18 (22.2) | 38 (25.3) | 26 (22.8) | 63 (15.1) | 31 (19.6) | |
Alcohol intake (yes) | 11 (9.3) | 8 (9.9) | 12 (8.0) | 9 (7.8) | 13 (3.2) | 11 (7.0) | 0.039 |
Smoking (yes) | 3 (2.5) | 2 (2.5) | 3 (2.0) | 2 (1.8) | 4 (1.0) | 2 (1.3) | 0.796 |
Regular exercise | | | | | | | |
Never | 16 (13.6) | 8 (9.9) | 11 (7.3) | 21 (18.4) | 127 (31.2) | 29 (18.4) | < 0.001 |
Rarely | 42 (35.6) | 25 (30.9) | 54 (36.0) | 33 (28.9) | 100 (24.6) | 58 (36.7) | |
Sometimes | 46 (39.0) | 34 (42.0) | 62 (41.3) | 42 (36.8) | 138 (33.9) | 57 (36.1) | |
Almost everyday | 14 (11.9) | 14 (17.3) | 23 (15.3) | 18 (15.8) | 42 (10.3) | 14 (8.9) | |
Family history dx. | | | | | | | |
Hypertension | 17 (14.4) | 11 (13.3) | 21 (14.0) | 25 (21.9) | 77 (18.9) | 30 (19.0) | 0.387 |
Diabetes | 25 (21.2) | 17 (21.0) | 31 (20.7) | 25 (21.9) | 73 (17.9) | 37 (23.4) | 0.755 |
Obesity* | 12 (12.4) | 7 (10.1) | 14 (9.3) | 11 (12.6) | 26 (11.2) | 12 (9.5) | 0.933 |
Measurements | | | | | | | |
Height (cm) * | 170.2 ± 9.0 | 167.2 ± 7.5 | 164.9 ± 9.2 | 168.8 ± 9.5 | 165.6 ± 8.4 | 166.8 ± 8.7 | < 0.001 |
Weight (Kg) * | 65.3 ± 10.5 | 63.2 ± 8.9 | 63.9 ± 11.4 | 66.1 ± 11.2 | 63.2 ± 10.1 | 64.0 ± 10.4 | 0.110 |
WC (cm) * | 73.9 ± 7.4 | 73.0 ± 5.9 | 73.0 ± 8.0 | 73.6 ± 8.2 | 72.6 ± 7.1 | 72.7 ± 6.9 | 0.499 |
BMI (Kg/m2) * | 22.6 ± 3.3 | 22.7 ± 3.5 | 23.5 ± 3.7 | 23.2 ± 3.3 | 23.1 ± 3.6 | 23.0 ± 3.6 | 0.330 |
RFM (cm/cm) * | 18.4 ± 4.5 | 19.0 ± 4.5 | 19.8 ± 4.5 | 18.5 ± 4.7 | 19.1 ± 4.8 | 18.8 ± 4.7 | 0.152 |
BF%^ | 22.0 ± 11.5 | 24.4 ± 11.1 | 28.2 ± 10.5 | 23.9 ± 10.3 | 25.8 ± 11.9 | 25.1 ± 11.9 | < 0.001 |
Visceral fat ^ | 4.0 ± 2.1 | 3.7 ± 1.6 | 4.2 ± 1.7 | 4.4 ± 2.3 | 4.0 ± 1.9 | 4.0 ± 1.8 | 0.247 |
* Variables are presented as mean and standard deviations and compared using a one-way analysis of variance; ^ values are presented as means but compared using Kruskal-Willi’s test. All other variables are presented with count and corresponding proportions.
Prevalence of being overweight and Obese based on standard BMI thresholds.
Using BMI ≥ 25.0 Kg/m2, approximately 31% and 15% of female and male students were classified as overweight/obese. However, only 2.4% of male students and 8.0% of female students were classified as obese using BMI ≥ 30.0 Kg/m2 (Table 3). We observed a trend towards increased overweight/obesity with age. Among students < 20 years, 26.6% and 13.5% female and male, respectively, were classified as being overweight and/or obese. Among ≥ 20 years female and male students, 34.5% and 15.5% were classified as overweight and/or obese.
Table 3
Estimate of overweight/obesity prevalence based on body mass index.
Obesity definition | Male students | Female students |
< 20 years (n = 170) | ≥ 20 years (n = 284) | Total (n = 454) | < 20 years (n = 266) | ≥ 20 years (n = 307) | Total (n = 573) |
BMI criteria | | | | | | |
25.0-29.9 | 20 (11.8) | 36 (12.7) | 56 (12.3) | 54 (20.3) | 77 (25.1) | 131 (22.8) |
≥ 30.0 | 3 (1.8) | 8 (2.8) | 11 (2.4) | 16 (6.0) | 29 (9.4) | 46 (8.0) |
The values shown are the actual number of individuals and gender-specific percentages.
Evaluation of RFM and BAI-derived TPBF based on BMI.
Passing and Bablok regression analysis are shown in Table S1. Here we emphasised the interpretation based on the observed random difference. The null assumption was that the observed random differences within ± 1.96 residual standard deviation (RSD) > 10%. Linearity between the variables was evaluated based on the custom test for linearity probability value (Table S1, Figure S1). Concordance was observed between TPBF and BMI (RSD = 1.60, ± 1.96 = -3.14 to 3.14) compared with RFM (RSD = 2.64, ± 1.96 = -5.17 to 5.17) among male students. Similarly, among female students, TPBF demonstrated good agreement with BMI (RSD = 2.23, ± 1.96 = -4.37 to 4.37) compared to RFM (RSD = 2.98, ± 1.96 = -5.83 to 5.83). The linearity test revealed a significant deviation from linearity between TPBF and BMI (p-value < 0.01) and between BMI and RFM (p-value > 0.05). The ROC curve analysis (Fig. 1) identified a TPBF threshold values of > 20.3% and > 20.8% and was associated with high information values for defining being overweight (BMI > 29.9 Kg/m2) among male students: 15–19 years (AUC = 0.941, sensitivity = 100.0%, specificity = 87.8%) and 20–25 years (AUC = 0.942, sensitivity = 94.4%, specificity = 89.6%), respectively. Also, TPBF threshold values for defining obesity (BMI ≥ 30.0 Kg/m2) among 15–19 years and 20–25 years female students were > 35.4% and > 35.2%, respectively (Fig. 1).
An optimal threshold value for TPBF > 26.2% (AUC = 0.981, sensitivity = 100.0%, specificity = 95.2%) for males (15–19 years) and > 24.4% (AUC = 0.938, sensitivity = 80.0%, specificity = 92.0%) had exceptional diagnostic accuracy for obesity (BMI ≥ 29.9 Kg/m2) among male students (Fig. 2). The TPBF threshold of > 35.4% and > 35.2 was optimal for defining overweight female students 15–19 years and 20–25 years, respectively. TPBF values > 41.8% and 44.3% were optimal for defining obesity among female students 15–19 years and 20–25 years.
ROC curve analysis of RFM for defining overweightness revealed an optimal cut-off of > 18.6 and > 20.5 among 15–19 years and 20–25 years male students, respectively (Fig. 1c and f). RFM thresholds for defining obesity were > 25.4 and > 22.6 among male students 15–19 years and 20–25 years respectively (Fig. 2a and f). Among female students (Fig. 3a and b), RFM thresholds of > 20.7 and > 20.9 were associated with high information values for defining overweight among 15–19 years and 20 − 15 years, respectively. Moreover, obesity definition thresholds were > 24.5 and > 25.2, respectively among female students 15–19 years and 20 − 15 years (Fig. 3c and d).
The concordance between BMI, TPBF and RFM for obesity classification was 84% (95% lower limit = 82.0%) among female students and 82.9% (95% lower limit = 80.5%) among male students. The findings of the posterior predictive checks using the simulated data are presented in Figure S3. The results of the Bayesian analysis suggest that the combined prevalence mean of overweight/obesity for TPBF and RFM were 33.8% (95%CI: 29.2%-38.6%) among female students and 17.0% (95%CI: 13.1%-21.3%) among male students. The combined prevalence mean of obesity for TPBF and RFM were 9.4% (95%CI: 6.9%-12.2%) among female students and 6.7% (95%CI: 4.3%-9.5%) among female students (Fig. 4).
Factors Associated with TPBF-defined Obesity among Students.
From the Multiple Logistic Regression analysis sex and family history of education were found to be consistent factors associated with general and central adiposity and percentage body fat distribution. The odds of being overweight were increased between 1.8 and 2.5, for women, depending on the classification criteria (Table 4). Family history of obesity was associated with increased odds of general obesity (OR = 3.48, 95%CI: 2.04–5.91), central obesity (OR = 1.98, 95%CI: 1.18–3.30) and high percentage body fat distribution (OR = 2.36, 95%CI: 1.42–3.94). Compared with level 100 students, the odds of central obesity and high percentage body fat were increased among level 300: OR = 2.77(1.59–4.82) and OR = 1.79(1.05–3.08), and level 400 students: OR = 3.26(1.76–6.04) and OR = 2.34(1.29–4.23), respectively.
Table 4
Multiple Logistic Regression analysis assessing factors associated with overweight/obesity prevalence among students.
Factors | BMI Threshold | TPBF threshold | RFM threshold |
OR (95%CI) | p-value | OR (95%CI) | p-value | OR (95%CI) | p-value |
Gender | | | | | | |
Male | 1 | | 1 | | 1 | |
Female | 2.30(1.60–3.51) | < 0.01 | 1.78(1.26–2.51) | 0.001 | 2.53(1.79–3.56) | < 0.001 |
Age (years) | | | | | | |
< 20 years | 1 | | 1 | | 1 | |
≥ 20 years | 1.41(0.84–2.36) | 0.198 | 0.63(0.39–1.02) | 0.060 | 0.78(0.49–1.24) | 0.294 |
Year of Study | | | | | | |
1st | 1 | | 1 | | 1 | |
2nd | 0.62(0.35–1.09) | 0.094 | 1.13(0.69–1.85) | 0.625 | 0.95(0.59–1.53) | 0.831 |
3rd | 1.18(0.65–2.15) | 0.577 | 2.77(1.59–4.82) | < 0.01 | 1.79(1.05–3.08) | 0.034 |
4th | 0.98(0.51–1.88) | 0.944 | 3.26(1.76–6.04) | < 0.01 | 2.34(1.29–4.23) | < 0.01 |
Regular exercise | | | | | | |
Never | 1 | | 1 | | 1 | |
Rarely | 1.64(0.70–3.82) | 0.702 | 1.01(0.49–2.11) | 0.974 | 1.16(0.55–2.40) | 0.692 |
Sometimes | 1.29(0.64–2.63) | 0.708 | 0.88(0.42–1.83) | 0.735 | 1.13(0.54–2.30) | 0.773 |
Almost everyday | 0.91(0.35–2.40) | 0.354 | 0.55(0.24–1.28) | 0.166 | 0.78(0.34–1.78) | 0.549 |
Alcohol intake (yes) | 0.90(0.45–1.77) | 0.750 | 0.94(0.91–1.76) | 0.854 | 0.85(0.46–1.59) | 0.613 |
Smoking (yes) | 0.31(0.03–2.70) | 0.286 | 0.20(0.03–1.75) | 0.146 | 0.86(0.19–4.01) | 0.852 |
Family history dx. | | | | | | |
Hypertension | 0.78(0.48–1.28) | 0.323 | 0.85(0.55–1.31) | 0.458 | 0.69(0.44–1.07) | 0.096 |
Diabetes | 1.19(0.75–1.89) | 0.457 | 1.22(0.80–1.86) | 0.354 | 1.16(0.76–1.76) | 0.496 |
Obesity | 3.48(2.04–5.91) | < 0.01 | 2.36(1.42–3.94) | 0.001 | 1.98(1.18–3.30) | 0.009 |
OR- odds ratios, CI- confidence intervals, BMI- body mass index, TPBF- total percentage body fat, RFM- relative fat mass, dx – diseases.