Shaping childhood obesity: behavioral and environmental risk factors associated with body mass index trajectories between 2 and 9 years in Samoan children.

Background/objective: Pacific children are at high obesity risk, yet the behavioral and environmental factors that contribute to obesity development in this setting remain poorly understood. We assessed associations between childhood risk factors for obesity with body mass index (BMI) trajectories between ages 2-9 years in Samoa.

Subjects/methods: In a prospective cohort of 485 children from 'Upolu, we measured weight and height at ages 2-4 (2015), 3.5-8 (2017-18), and 5.5-11 years (2019-20). Modern dietary pattern adherence was assessed using factor analysis of primary caregiver-reported food frequency questionnaire data. Physical activity was estimated with the Netherlands Physical Activity Questionnaire. Socioeconomic resources were assessed using an 18-item household asset score. Urbanicity was based on village residence. Associations of these risk factors with predicted weight, height, and BMI (at 1-year intervals and velocity) were assessed using multilevel cubic spline regressions.

Results: Females had greater adjusted weight velocity with high modern dietary pattern adherence compared to low (p-value for interaction with age spline term 1 = 0.028 and age spline term 2 = 0.007). Starting at age 3 years, children with higher physical activity had higher BMI, but this association was not meaningful up to age 9 (all p-value > 0.05). Males with very high compared to low household assets had higher BMI from age 2 to 4 years (95% CI: 0.26-1.53 kg/m², p = 0.006) and greater BMI velocity (p-value for interaction with age spline term 2 = 0.001). Males in the urban region had the greatest BMI gain after age 5 compared to the rural region (p-value for interaction with age spline term 2 = 0.014).

Conclusions: High, centile-crossing BMI trajectories suggest that obesity prevention and intervention are needed among Samoan children before age 9 years. Positive associations between high modern dietary pattern adherence, greater asset ownership, and urbanization offer initial insights into who, and which behavioral risk factors, should be prioritized in implementing public health solutions.