ABSTRACT
Objectives: To compare: (i) prevalences of thinness in schoolchildren by four body mass index references in common use viz., Centre for Disease Control (CDC); Cole; Indian Academy of Pediatrics (IAP); World Health Organization (WHO); and (ii) relationship of thinness with absence of cardio-metabolic risk factors in these BMI references. Design: Cross-sectional. Setting: Schools in Delhi. Participants: Anthropometry and blood pressure were measured in 16,245 school children aged 5 to 18 years. Fasting lipids and blood sugar were estimated in 2796 subjects. Outcome measures: Age and sex-specific prevalences of thinness and predictive ability of reference cut-off for detecting any cardio-metabolic risk factor were compared. Results: Prevalence of thinness varied with the reference employed; more so for boys. Overall prevalence of thinness was least with IAP reference and highest with CDC cut-offs (6.6% to 16.9% in boys, 6.5% to 10.3% in girls). Children identified as thin by any reference had comparable, significantly lower risks (OR 0.59 to 0.73) of associated cardio-metabolic aberrations. In subjects with any cardio-metabolic or blood pressure aberration, the prevalence of thinness was highest with CDC and least with IAP definition. Conclusion: Prevalence of thinness varies considerably with the reference employed. Thin children, identified by any reference, have a lower risk of associated cardio-metabolic aberrations; however, thinness is a poor diagnostic test for this purpose. In populations undergoing nutrition transition, there is a need to link cardio-metabolic risk factors with recommended anthropometric criteria to define undernutrition.