Tracking changes in weight status in primary school children in Birmingham: an analysis of the National Child Measurement Programme - a retrospective cohort study.

Unlabelled: One-in-four 4-5 years and more than one-in-three 10-11 years have excess weight in England.

Aim: To identify characteristics associated with (1) having overweight, obesity and severe obesity at 11 years and (2) rapid weight gain (defined as increasing weight status by one or more body mass index (BMI) categories) between the ages of 4-5 and 10-11 years.

Method: Using National Child Measurement Programme data, BMI at reception (4-5 years) and year 6 (10-11 years) were linked for 15 390 children. Weight categories were identified at both time points using BMI centile classifications.For each child, the number of BMI categories they crossed between reception and year 6 was identified. Logistic regression models were fitted to explore associations with sociodemographic characteristics of children with excess weight at age 10-11 years and with children experiencing rapid weight gain between reception and year 6.

Results: Overall, 61.9% of children remained in their original weight category; 30% whose weight increased by ≥1 weight categories and 11.7% by ≥2 weight categories. Only 7.8% had decreased ≥1 weight categories and 0.9% had decreased ≥2 weight categories.Adjusting for other sociodemographic characteristics, girls were less likely than boys to increase ≥2 weight categories between reception and year 6 (OR 0.64; 95% CI 0.58 to 0.71; p<0.001). Compared to white children, Asian and mixed-ethnicity children had higher odds of rapid weight gain. Children with the highest deprivation were over 6 times more likely to increase ≥2 weight categories between reception and year 6 compared with children with the lowest deprivation (OR 6.1; 95% CI 1.92 to 19.10; p<0.01).

Conclusion: Male children, children of Asian and mixed ethnicity and children with high deprivation are at higher risk of rapid weight gain and should be targeted for intervention.