BACKGROUND In 2009, the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) food packages were updated. WIC-participating children in Los Angeles County receiving the new food package, compared with the old, had lower obesity risk at age 4. OBJECTIVE To determine if the association between the new WIC food package and obesity varies by type of infant WIC food package received. DESIGN Longitudinal study using administrative data on children participating in WIC in Los Angeles County continuously from birth until age 4. Children were compared across periods: Before (period 1: born 2003-2004), straddling (period 2: born 2005-2008), and after (period 3: born 2009-2011) the food package change. Children were further grouped as Fully Breastfed, Mostly Breastfed, Mostly Formula Fed, and Fully Formula Fed based on the type of food packages received during the first year of life. PARTICIPANTS/SETTING WIC-participating children in Los Angeles County between 2003 and 2016 (N=116,991). MAIN OUTCOME MEASURES Weight-for-height z-score growth trajectories from 0 to 4 years and obesity (body mass index-for-age≥95th percentile) at age 4. STATISTICAL ANALYSES PERFORMED Children were matched across periods on infant feeding group; age, sex, race or ethnicity, and initial weight status; maternal education and language; and family poverty. Sex-stratified piecewise linear spline mixed models and Poisson regression models were fit to the data. RESULTS No differences across periods were observed for children in the Fully Breastfed group. Boys in the Mostly Breastfed (relative risk [RR]=1.27, 95% CI=1.17 to 1.38), Mostly Formula Fed (RR=1.07, 95% CI=1.02 to 1.13), and Fully Formula Fed (RR=1.13, 95% CI=1.06 to 1.20) groups in period 1 had higher obesity risk than their counterparts in period 3; girls in the Mostly Breastfed group in period 1 had a higher obesity risk than those in period 3 (RR=1.17, 95% CI=1.07 to 1.28). CONCLUSIONS The association between the WIC food package change and obesity varied by type of infant food package received, with the strongest associations observed for those who were mostly breastfed.

中文翻译：

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2009 年 WIC 食品包装变化与儿童早期肥胖风险之间的关联因收到的婴儿包装类型而异

背景 2009 年，更新了妇女、婴儿和儿童 (WIC) 食品包的特殊补充营养计划。洛杉矶县参与 WIC 的儿童与旧的相比，在 4 岁时的肥胖风险较低。 目的 确定新的 WIC 食品包与肥胖之间的关联是否因接受的婴儿 WIC 食品包的类型而异. 设计 使用洛杉矶县儿童从出生到 4 岁连续参与 WIC 的行政数据进行纵向研究。 对儿童进行跨时期比较：之前（时期 1：2003-2004 年出生），跨界（时期 2：2005-2008 年出生），以及之后（时期3：出生于2009-2011）食品包装变化。儿童进一步分为完全母乳喂养、大部分母乳喂养、大部分配方喂养、和全配方喂养，基于出生后第一年收到的食品包类型。2003 年至 2016 年期间洛杉矶县参与 WIC 的儿童（N=116,991）。主要观察指标 0 至 4 岁的身高别体重 z 值增长轨迹和 4 岁时的肥胖（年龄别体重指数≥95%）。进行的统计分析 年龄、性别、种族或民族，以及初始体重状况；母亲教育和语言；和家庭贫困。性别分层分段线性样条混合模型和泊松回归模型适合数据。结果 完全母乳喂养组的儿童在不同时期未观察到差异。大部分母乳喂养的男孩（相对风险 [RR]=1.27，95% CI=1.17 至 1.38），大部分配方喂养（RR=1.07，95% CI=1.02 至 1.13），以及全配方喂养（RR=1.13，95% CI=1.06 至 1.20）组在第 1 阶段的肥胖风险高于第 3 阶段的对应组；第 1 阶段主要母乳喂养组的女孩比第 3 阶段的女孩具有更高的肥胖风险（RR=1.17，95% CI=1.07 至 1.28）。结论 WIC 食品包装变化与肥胖之间的关联因收到的婴儿食品包装类型而异，观察到的关联最强的是那些大多是母乳喂养的婴儿。