Three Decades of New Zealand Adults Obesity Trends: An Estimation of Energy Imbalance Gaps Using System Dynamics Modeling.

OBJECTIVE

The energy imbalance gap (EIG) captures the average daily excess energy intake and governs the speed of change in body mass. This study quantifies the dynamics of the EIG over time and across different ethnic, sex, and weight groups in New Zealand.

METHODS

A novel method in system dynamics was used to estimate the trends/dynamics of the EIG among Pacific, Māori, Asian, and European/other men and women over the past 3 decades in New Zealand. The model was calibrated using data from the national New Zealand Health Survey (1988-2014/15).

RESULTS

All ethnic/sex subpopulations except European/other women and Pacific men showed a drop in their EIGs starting in early to mid-2000. For European/other subpopulations, the EIG was positive in 2014/15 but lower than it was in previous years, meaning that the prevalence of obesity still increased but at a slower pace. For the Pacific subpopulation, increasing trends of the EIG across all BMI classes in 2014/15 implied that obesity prevalence for this subpopulation increased at a rate faster than before. Among Asian women, almost all BMI classes showed a negative EIG in 2012 to 2014/15, implying decreasing prevalence of obesity in this subpopulation. Māori populations with obesity showed a negative EIG in 2014/15.

CONCLUSIONS

The detailed heterogeneous trends of the EIG explain the obesity patterns for different ethnic, sex, and BMI subgroups in New Zealand and suggest the need for customizing targets/policy interventions for different subpopulations.