While there is increasing international evidence for the widening of the distribution of body mass index (BMI), there has been little attempt to explain this trend. The aim of our study is to examine whether the trend can be explained by compositional changes within the population or contextual changes in the relationships between explanatory variables and BMI. Data from the Health Survey for England for 2002–2004 and 2012–2014 were used. BMI was our outcome variable and explanatory variables included age, sex, race, education, occupation, and physical activity. We examined how predictors of BMI varied at the 10th, 50th, and 90th percentiles using unconditional quantile regressions. Oaxaca-Blinder type decomposition analysis was then applied to examine whether contextual or compositional explanations accounted for changes in the distribution between time periods. We found that changes in the nature of relationships observed by our coefficient values accounted for the majority of the difference in BMI at the 90th percentile in 2012–2014 compared to 2002–2004. Race, physical activity, and socio-economic status were the primary reasons for explaining the continued growth of the right tail of the BMI distribution. Compositional changes in the population were less influential, but may have offset some of the contextual changes to relationships. Changing relationships between predictors of BMI reflect systematic changes in the determinants of BMI, leading to the widening of the BMI distribution. Our results demonstrate the importance of multi-tiered policies aimed at tackling the varying influences across the BMI distribution.

中文翻译：

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解释体重指数分布的扩大：2002-2004 年和 2012-2014 年英格兰趋势的分解分析

虽然越来越多的国际证据表明体重指数 (BMI) 的分布范围在扩大，但几乎没有人试图解释这种趋势。我们研究的目的是检验这种趋势是否可以通过人口的组成变化或解释变量与 BMI 之间关系的背景变化来解释。使用了 2002-2004 年和 2012-2014 年英格兰健康调查的数据。BMI 是我们的结果变量，解释变量包括年龄、性别、种族、教育、职业和身体活动。我们使用无条件分位数回归分析了 BMI 的预测因子在第 10、50 和 90 个百分位数上的变化情况。然后应用 Oaxaca-Blinder 类型分解分析来检查上下文或成分解释是否解释了时间段之间分布的变化。我们发现，与 2002-2004 年相比，2012-2014 年第 90 个百分位的 BMI 差异主要是由我们的系数值观察到的关系性质的变化造成的。种族、身体活动和社会经济地位是解释 BMI 分布右尾持续增长的主要原因。人口的组成变化影响较小，但可能抵消了关系的一些背景变化。BMI 预测因子之间变化的关系反映了 BMI 决定因素的系统变化，导致 BMI 分布的扩大。