Waist Circumference, Waist-to-Height Ratio and Body Mass Index as Parameters of Obesity Among Public Secondary School Students

Abstract

Background: Obesity in children is universal affecting all ethnicities, ages, gender and social classes. Public school children consist mainly of the less affluent strata of society, and consequently may not be opportuned to avail themselves of necessary public health interventions as their private school counterparts.          Objective:This study aimed to determine the prevalence of obesity using various anthropometric indices and association of certain factors with obesity among public secondary school students.    Methods:A cross-sectional school-based questionnaire and physical assessment of 593 students aged 10 – 17 years in public schools in Nnewi, Southeast Nigeria was carried out.                                                             Results: There were 289  boys and 304 girls, giving an approximate ratio of 1:1. Most of the students were from the middle and lower socio-economic levels. Girls were physically less active and consumed more junk food than the boys. The mean weight and height varied significantly with age in males, females and both sexes combined together (p <0.001). In general, girls were heavier than boys, while the boys were slightly taller than the girls. Age varied significantly with BMI (P<0.001 for girls and boys), WC (P<0.001 for girls and boys) and WHtR (p=0.034 for boys and 0.024 for girls). BMI performed better than WC and WHtR in identifying children with obesity. When compared with BMI, WC had a sensitivity of 5.2% and a specificity of 100.0% with a positive predictive value of 100.0% and a negative predictive value of 90.7%. WHtR had a sensitivity of 31.0% and a specificity of 99.8% with a positive predictive value of 94.7% and a negative predictive value of 93.0%. BMI had a strong correlation with both WC and WHtR although correlation was stronger with WC (R=704) compared to WHR (R=641). Among the students 9.8% were in the obese/overweight group, made up of 96.6% females, out of which 64.1% were older adolescents aged 15-17 years. Reduced physical activity played a major role in enhancing obesity/overweight, while socio-economic level and diet did not. After logistic regression analysis, age and sex remained significantly associated with being overweight or obese. The odds of being overweight or obese was 32 times in females compared to males and twice in in late adolescence compared to early adolescence.                                                                                                                                      Conclusion:  The obesity/overweight of older adolescent public secondary school girls buttress the importance of physical exercises in curbing obesity. Although easier to perform and very specific, WC and WHtR seemed to miss many adolescents with obesity when compared to BMI.  Therefore, a combination of these indices is recommended while screening adolescents for obesity.