Trajectories of the double burden of malnutrition and social inequality in 6–12-year-old South African children: The NW-child study

The definition of the double burden of malnutrition is inconsistent, and longitudinal evidence from mid-to-late childhood, when adiposity typically increases, remains limited. Little is also known about how these patterns differ according to socio-economic status (SES). We longitudinally investigated the population-level double burden of malnutrition by SES, using multiple proxy measures of malnutrition in South African boys and girls. This study used data (2010–2016) from the North-West Child-Health-Integrated with Learning and Development longitudinal study, South Africa. The same children ( N = 333) were followed across Grades 1 (6–7 years), 4 (9–10 years), and 7 (12–13 years). Prevalences and odds of malnutrition were determined in boys and girls of low ( n = 186) versus high ( n = 147) SES. At risk of undernutrition (≤ − 1 SD) was defined by height-for-age (HAZ), weight-for-age (WAZ), and body mass index-for-age (BAZ); overnutrition by BAZ (≥ + 1 SD), waist-to-height ratio (WHtR; ≥ 0.5), and body fat percentage (BF%; ≥ 25% boys, ≥ 30% girls) using an Omron BF 511. Significantly (all p ≤ 0.001) more children of low SES were classified as at risk of stunting and underweight, with significantly higher risk of underweight (at risk of stunting: ≥ 178% and underweight: ≥ 259%), across Grades 1 to 7. Significantly fewer children of low SES were overweight or obese by BAZ, WHtR, and BF%, with a lower risk of overweight or obesity (WHtR: ≥ 68%, BF%: ≥ 68%, and BAZ: ≥ 71%), across Grades 1 to 7 (all p ≤ 0.003). In pubertal boys, stunting prevalence increased by 24.1%, but in pubertal girls, the higher risk of being classified as at risk of stunting and the lower risk of overweight or obesity (BAZ) lost significance over time. In this South African cohort, persistent trends of being at risk of undernutrition were observed in children of low SES status, and overnutrition in high SES. The prevalence of stunting risk increased in low-SES pubertal boys, with some adiposity and growth rebound in low-SES pubertal girls. A population-, but not individual- level double burden of malnutrition was evident, supporting SES-specific preventive strategies during childhood.