Application of Stable Isotope Dilution Techniques to Assess Body Fat and Comparison with WHO BMI-For-Age Classification as a Measure of Obesity among Schoolchildren in Nairobi, Kenya
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Date
2021
Authors
Kigaru, Dorcus Mbithe D
Ndung’u, Zipporah W
Macharia-Mutie, Catherine W
Journal Title
Journal ISSN
Volume Title
Publisher
Cambridge University Press
Abstract
Objective: WHO BMI-for-age z score (BAZ) is widely used in epidemiology, yet it
does not distinguish body fat-free mass and fat mass which are better indicators of
obesity and related risks. The stable isotope dilution techniques (SIDT) are gold
standard methods of assessing body composition. Main objective was to assess significant differences in measurement and validity of WHO BMI-for-age classification
for defining childhood obesity by comparing with body fatness using SIDT among
schoolchildren.
Design: A cross-sectional analytical study. A questionnaire, anthropometry and
body composition data were used. SPSS was used to analyse data at P < 0·05 at
95 % CI.
Setting: Primary schools in Nairobi City County, Kenya
Participants: One hundred seventy-nine schoolchildren aged 8–11 years were
randomly sampled.
Results: Prevalence of adiposity by reference SIDT (24·0 %) was significantly higher
than that of obesity by BAZ > 2 SD (2·8 %) (Wilcoxon test, P < 0·05). Concordance
coefficient between SIDT and BAZ > 2 SD in diagnosing obesity was poor
(κ = 0·167). Only 11·6 % of children with excess body fat were correctly diagnosed
as obese by BAZ > 2 SD. The use of BAZ > 1 SD for overweight and obesity showed
fair concordance coefficient (κ = 0·409, P < 0·001) with 32·5% of children with
excess fat positively identified as overweight and obese.
Conclusion: WHO BMI-for-age cut-off points severely underestimate the prevalence of overweight and obesity compared with body composition assessment
by stable isotope dilution techniques. Evidence-informed interventions should
be based on more accurate estimates of overweight and obesity than that can
be provided by BAZ.
Description
Article
Keywords
Obesity, Body fat, BMI-for-age, Stable isotope
Citation
Kigaru, D. M. D., Ndung’u, Z. W., & Macharia-Mutie, C. W. (2021). Application of stable isotope dilution techniques to assess body fat and comparison with WHO BMI-for-age classification as a measure of obesity among schoolchildren in Nairobi, Kenya. Public Health Nutrition, 24(12), 3587-3591.