The Assessment of Nutritional Status of Adolescents Aged 15-18 Years Using BMI Cutoffs and BMI Z Scores: A Secondary Analysis of National Family Health Survey-5 (2019-21) Data.

ABSTRACT

BACKGROUND: Appropriate assessment of nutritional status of adolescents as a population group is an important area of focus, considering the age of culminating growth, the size of the age group, the changing nutrition patterns, and as a window of opportunity for corrections before adulthood sets in. Nutritional status is now recognized to be a prime indicator of the health of individuals. The World Health Organization (WHO) emphasizes the importance of employing age- and sex-specific reference values (body mass index-for-age Z scores {BAZ} scores) for nutritional assessment in this age group. However, the National Family Health Survey (NFHS), the major source of data in India for the policymakers, reports the nutritional status of adolescents based on adult body mass index (BMI) cutoffs, which might not be as appropriate as compared to body mass index-for-age Z scores (BAZ) scores. Misclassification of nutrition status has impacts on public health policies, intervention programs, and long-term health outcomes for adolescents. METHODS: This secondary analysis of NFHS-5 data was performed with the objective of estimating the degree of agreement between BMI and BAZ cutoffs in classifying the nutritional status among Indian adolescents. The NFHS-5 data were collected from over 636,000 households across the country. Height and weight were measured for adolescents using standardized instruments. BMI and BAZ scores were derived to assess nutritional status. World Health Organization's classifications were used to categorize nutritional status based on BMI and BAZ scores. The final analysis included data from 109,340 adolescents (13,040 males and 96,300 females) after excluding subjects having BAZ outliers and those whose age was 179 months or less. RESULTS: Substantial discrepancies emerged between the two methods. BMI classifications underestimated nutritional status in almost 30% of adolescents compared to BAZ. Over one-third of normal-weight individuals by BAZ are classified as thin by BMI. Conversely, nearly 78% of obese adolescents by BMI are classified as overweight by BAZ. The agreements between the classifications improved with age and were better among males. CONCLUSION: This analysis highlights the limitations of BMI for assessing adolescent nutritional status and suggests that BAZ offers a more accurate and age-appropriate alternative.