A three-year multifaceted intervention to prevent obesity in children of Mexican-heritage

Pediatric obesity and overweight prevalence has more than tripled from 1971 to 2011 [1], triggering health problems including high blood pressure, type 2 diabetes, and elevated blood cholesterol levels [2]. Common co-morbidities include low self-esteem, negative body image, and depression. According to the American Heart Association, these health issues are occurring earlier in life and are linked to an accelerated risk of obesity-related disease and earlier death in adulthood [3‐5]. The incremental health care costs of pediatric obesity are estimated at $14 billion [6].

Two-thirds of Latinos living in the US are Mexican-heritage. At 17.8% of the total population, as of 2016, the Latino community is the majority minority population in the US [7]. Most recent data (2011–2014) indicate 22.4% of Hispanic males and 21.4% of Hispanic females ages 2–19 in the US are obese compared with 14.3% of Non-Hispanic white males and 15.1% of Non-Hispanic white females in the same age category [8]. Additionally, a recent study from Northern California found that 18.2% of Hispanic boys and 15.2% of Hispanic girls, ages 3–5 years, were obese [9]. Preventive strategies targeting Mexican-American children at risk of obesity are critical. An increasing number of community-based interventions report body mass index (BMI) outcomes in Latino children [10‐15]. Study characteristics associated with improved BMI outcomes include longer duration and/or greater intensity of intervention, targeting parenting skills, having dedicated staff, and utilizing behavior-change theories [11]. Noticeably missing in the literature, however, are long-term, community-based interventions addressing the economic and cultural factors in predominantly rural Mexican origin communities at high risk of childhood obesity. High rates of poverty, food insecurity, and social isolation in these communities create challenges that may require long-term economic and educational components to reverse childhood obesity trends [16, 17]. Successful interventions may include culturally nuanced education targeted towards both caregivers and children combined with economic supports to purchase healthy foods. Furthermore, it is important that interventions focus on all children, as normal and overweight children are at still at risk of becoming obese.

Niños Sanos, Familia Sana (NSFS - Healthy Children, Healthy Family) measured the impact of a multifaceted, community-based intervention on children’s BMI in an underserved, rural Mexican-heritage community in California’s Central Valley. The intervention and comparison communities in this study match residential environment and demographics of the majority of California’s agricultural workforce [18]. Gender differences in response to the intervention were examined because national data [19] for Mexican-American adolescents indicate higher prevalence of overweight and obesity among boys (27.9%) compared to girls (18.0%). Given the relatively long duration of the intervention, age group at the start of the intervention was also expected to influence growth trajectory. This goal of the intervention was to reduce the rate of BMI growth among participating children and this paper addresses the changes in anthropometric measures that occurred from baseline to the end of the three-year intervention.

Figure 1 displays the flow of participating children across the intervention and comparison groups. Throughout the study, 782 children were eligible and had parental/guardian consent, including 430 in the intervention group and 352 in the comparison group. Retention rates for the intervention-group and comparison-group were 76.0% (n = 328) and 78.1% (n = 275), respectively. The analytical sample included children with at least one set of anthropometric measurements at any point during the study, including those who exited before study completion: 387 and 313 in the intervention and comparison groups, respectively. Children who exited had younger and less acculturated mothers than children who completed the study. There was no difference in zBMI or BMI percentile between those who exited and remained (data not shown).

Table 1 shows baseline characteristics. Comparison-community mothers were significantly younger, less educated, and more likely to have been born in Mexico than intervention-community mothers. The multivariate analysis controlled for these variables. Otherwise, differences were not statistically significant between communities in any other baseline characteristics.

Table 2 presents regression results with log-BMI and zBMI as outcomes. After controlling for age group, mother’s birth place, and obesity status at the time of enrollment; time-interval from baseline to measurement (days); and participation duration, the intervention group (1 = treatment; 2 = comparison) was significantly associated with both log BMI (β = 0.04 (0.02), P = 0.03) and zBMI (β = 0.25 (0.12), P = 0.04) among boys. Among girls, the intervention term was only significant for children who were obese at baseline (ref normal wt status) (β = − 0.04 (0.02), P = 0.04). To examine the magnitude of the intervention’s effect on BMI, we ran a series of models for each gender with all the predictors fixed except interactions between age group and obesity status at baseline with the intervention. The intervention was significantly and inversely associated with BMI in obese boys in all age groups and normal weight boys in the oldest age group (over 6 years). The intervention resulted in significantly lower BMI in obese girls in all three age groups relative to their counterparts in the comparison group.

Figure 2 presents the CDC expected BMI (50th percentile by age in months) along with NSFS participants’ observed BMI, stratified by community, gender, and obesity status at baseline. In boys across all three categories of baseline obesity status, BMI in the comparison group is higher than the intervention group at the older end of the age spectrum. Overall, obese girls in the comparison community have higher BMI relative to the intervention site, however the gap widens among older girls.

Table 3 presents regression results with WCHTR as the outcome. The results for boys’ WCHTR were similar to BMI. The intervention term was insignificant in models of girls’ WCHTR.

Exploration of the three-way interaction of age group, intervention and baseline obesity status yielded insignificant associations of terms with outcomes (data not shown).

The multifaceted intervention in this study reduced BMI trajectory in obese boys and girls, across all age groups, in the intervention community relative to the comparison community. The intervention was also associated with lower BMI trajectories for normal weight boys and girls in the oldest age category (over 6 years), however this difference was only significant for boys. WCHTR, another measure of adiposity, was significantly and inversely associated with the intervention for obese boys and older boys in all weight categories.

These findings are similar to those reported by several studies targeting Latino children. Like NSFS, Barkin et al. reported obese children to have the largest reduction in BMI in response to their intervention [12]. Both studies targeted Latino children, starting at ages 2–6 years, through culturally-adapted educational interventions focusing on nutrition, physical activity, and parenting skills. In a non-randomized study targeting Mexican-American children in Headstart centers, Yin et al. observed more favorable pre-post changes in weight z-score in the group receiving an 18-week center- and home-based intervention, compared to a nonintervention group [34]. Haines et al. [35] randomized 121 low-income, predominantly Hispanic, families to a six-month educational intervention. Themes were similar to those presented in NSFS and focused on household routines, including family meals, sufficient sleep time, and limits on TV time. Intervention children showed significant decreases in BMI. However, Alexander et al. [15] did not find that a school-based, multifaceted intervention targeting first and second graders decelerated BMI gains over a six-month follow-up period among the most obese children, though improvements were observed in overweight children.

Most interventions targeting this population have been considerably shorter in duration than NSFS [12, 13, 34, 35]. However, Aventuras Para Niños (Adventures for Children) [13] was a three-year intervention with a factorial design that examined the effect of family- and/or community-level interventions on BMI and behavioral outcomes. Although significant changes in parenting behaviors occurred, no improvements in children’s zBMI or BMI percentiles were observed, either in the total sample or by gender and initial BMI status. That study did not report on differences in BMI trajectories. Important differences that may have influenced outcomes include location of site (NSFS, rural vs. Aventuras, urban); provision of an economic incentive in NSFS (no incentive in Aventuras); and younger age of children at baseline in NSFS (3–8 years) compared to Aventuras (K-1st grade).

Similar to the studies cited above [12, 13, 15, 34, 35], NSFS did not result in a significant effect on zBMI in girls. Instead, log BMI as an outcome revealed changes that might be expected in sample subgroups. Other researchers have noted that zBMI may not be the optimal measure for assessing adiposity change over time in young children and adolescents [36]. Both log BMI and zBMI models show the significant effect of intervention in the older children group. However, only the log BMI model detects a significant impact of intervention on children with obesity at the baseline. We believe the reasons that the zBMI model fails to detect this association are twofold. First, according to the CDC the standard growth charts do not accurately estimate very high BMIs. In our sample, 26.7% of children have BMI over 95th percentile. Second, in longitudinal and intervention studies the changes in L (normality) and S (dispersion) parameters are particularly large in very high BMI children and cause even more instability in zBMI [29, 30, 37].

In long-term, community-based obesity prevention studies that include all healthy children with normal, overweight, or obese weight status at baseline, it is not surprising to find certain subgroups responding more strongly than others to the intervention. In a review of interventions among Latino children, Branscum and Sharma noted that the more successful interventions had targeted children at higher risk (more overweight and obese) with more room for improvement [11]. An intervention’s potential to impact growth trajectories might also be expected to differ by age; more success has been documented in children 6–11 years, compared to younger or older children [38]. Gender differences also can influence response to an intervention. Growth trajectories for sons of Mexican-American immigrant mothers begin to increase sharply around 4.5 years, a pattern not observed in girls [39]. This gender effect may explain why an interaction between the intervention and older age (over 6 years) was observed in boys but not girls. NSFS researchers previously reported that the rate of BMI growth for obese boys slowed significantly after the first intervention year [40], whereas the response for obese girls was delayed until the third year. In Mexico, a preference for sons, coupled with indulgent feeding of boys, has been attributed to heavier body weights [41]. Messages in NSFS classes discouraged indulgent feeding, which may have had a differential impact on boys. Furthermore, Latino parents tend to become concerned when their children become obese, as opposed to overweight, and apply different standards to boys and girls [42]. Therefore, parents may be slower to recognize or respond to a problem in daughters than sons, suggesting value to gender-nuanced strategies within this population.

This study has some limitations. The intent-to-treat analysis assumes intervention compliance and does not consider the dose-response of individual components in the intervention package. For example, not all parents attended the same number of nutrition education workshops. Furthermore, the study population is homogenous and culturally unique, and results may not be generalizable to a more diverse set of children. The sample homogeneity may restrict the ability to examine covariates known to be correlated with child weight, including acculturation and mother’s education and age. Finally, a cluster-randomized design, including more than two communities per treatment, would have been a stronger design, however was not feasible due to scope and funding.

This study also has a number of strengths. This is one of the first long-term studies to focus on young Mexican-heritage children in a rural setting. The study benefited from broad participation of a transdisciplinary research team of doctors, nutritionists, economists, and behavioral scientists who collaborated with community members and school district leaders to design and implement an intervention that addressed both knowledge gaps and socioeconomic barriers to maintaining a healthy weight.

A community-based, multifaceted intervention was effective in slowing the BMI growth rate among obese Mexican-heritage children and normal weight boys older than 6 years old. In addition, girls and boys respond differently, implying gender specific strategies should be considered. The findings also suggest that to enhance effectiveness of interventions, clinicians should work with a variety of community-based stakeholders, including parents, school officials, and policy makers.