Overweight risk in early adolescence according to children's BMI growth channelling changes in international growth standard/references.

Objective: To compare the international BMI standard/references of the International Obesity Task Force (IOTF), MULT and the WHO and to analyse the association between changes in BMI growth channelling (BMI-GC) during childhood and the risk of being overweight in early adolescence.

Design: Participant data from the Millennium Cohort Study (MCS), young lives (YL) and Generation XXI (G21) cohorts were obtained at three time points. Lin's concordance correlation coefficient (CCC) and the weighted Kappa coefficient were used to assess the agreement among the BMI standard/references. The relative risk (RR) of being overweight at 9·5-13·5 years, based on an increase in BMI-GC (amplitude ≥ 0·67) between 3·5-6 years and 6·5-9 years, was calculated, with estimates adjusted for sex, ethnicity and socio-economic status.

Setting: Ethiopia, India, Portugal, Vietnam and United Kingdom.

Participants: Totally, 12 624 participants from the MCS, YL and G21 studies.

Results: The prevalence of overweight across the three ages groups was higher when using the WHO standard/reference (12·8-25·9 %) compared with the MULT (17·1-22·9 %) and IOTF (13·0-19·3 %) references. However, substantial agreement (0·95 < CCC ≤ 0·99) was found among these standard/references. Children who increased their BMI-GC by ≥ 0·67 and < 0·86 were more likely to be overweight at 9·5-13·5 years (MULT-RR = 2·49, 95 % CI: 2·00, 3·09/ WHO-RR = 2·47, 95 % CI: 1·96, 3·12/ IOTF-RR = 2·31, 95 % CI: 1·82, 2·93), compared with those who have stayed in their BMI-GC.

Conclusions: A change in the BMI-GC among normal-weight children during childhood was associated with a significantly higher risk of being overweight at 9·5-13·5 years. These findings suggest that monitoring BMI-GC in children could be a tool to intervene and to prevent overweight in early adolescence.