Validation Of Nutritional Status Assessment Methods Using Stable Isotope Dilution Technique Among School Children In Nairobi City County, Kenya

ABSTRACT 

Methods used to assess overweight and obesity generate information that can be used to design interventions and policies which can address over-nutrition. Dietary practices, physical activity and anthropometry are the commonly used methods for assessing overweight and obesity. However, studies have cited their limitations since these methods do not indicate fat mass which is the factor that predisposes individuals to weight-related health risks. This study aimed to validate anthropometry, dietary practices and physical activity as commonly used methods for assessing overweight and obesity using stable isotope dilution technique (SIDT) as the gold standard for measuring body fat (BF). The study further aimed to model prediction equations for estimation of body fat among Kenyan children. A cross-sectional analytical study design was used to collect both qualitative and quantitative data from 202 randomly selected children aged 8-11 years in four randomly selected schools in Kasarani sub-county, Nairobi. Data were collected on demographic characteristics of the children, dietary practices, physical activity, anthropometric measurements, and body composition measurements. Anthropometric data were analyzed using WHO anthroplus software. The distribution of body mass index (BMI)-for-age z-scores and waist to height ratio (WtHR) were categorized according to WHO guidelines. Saliva samples for determination of body composition were analyzed using Fourier Transform Infrared Spectrometry. Physical activity score was calculated from the total score of nine questions in physical activity questionnaire for children and accelerometer data was analyzed using Acti-life computer software. Nutrient intake was analyzed using Nutri-Survey software. Relationships between variables were established using Pearson correlation, odds ratio and chi-square while differences were established using t-test and Wilcoxon test. Validation was done using Cohen’s Kappa coefficient and Bland-Altman analysis. Multiple regression was used to model equations. The mean percent body fat was 27.52±6.4 for girls and 19.65±5.9 for boys with 24.0% of children having excess fat. The mean BMI-for-age was 16.0±2.4 with 5.0% being overweight and 3.0% obese. Central obesity using WtHR was 6.9%. Children with excess energy intake above 120% of RDAs were 29.7%. Energy intake significantly correlated with body fat (r = 0.621, P