A natural experiment: The opening of a supermarket in a public housing community and impacts on children's dietary patterns.

Objective: The aim of the present study is to utilize a natural experiment and examine changes in dietary patterns of predominantly low-income, racial and ethnic minority children who live in a public housing community following the opening of a new supermarket. Methods: Data comes from the Watts Neighborhood Health Study (WNHS), an ongoing study in South Los Angeles, United States, that follows residents of Jordan Downs, a public housing community undergoing redevelopment. Surveys were administered to children aged 9-17 years (n = 297), as well as an adult in the household. The second baseline data collection was conducted June-December 2019, and follow-up was conducted June 2020-April 2021, shortly after the introduction of the new supermarket in January 2020. ANCOVA linear regression models were estimated to examine the association between children's proximity to the new supermarket with dietary outcomes at follow-up. Interactions with barriers to food access were also explored. Results: Living close to the new supermarket was not significantly associated with dietary outcomes at follow-up. However, for children who lived in households with no vehicle access, living close to the new supermarket was associated with increased fruit and vegetable consumption, compared to children in the comparison group. Conclusion: Proximity to the new supermarket was not associated with improved dietary outcomes among children unless they had transportation barriers. This adds to the growing body of literature that suggests that the effects of neighborhood food environments may be modified by individuals' mobility, and that comprehensive interventions are needed.

Heterogeneity in COVID-19 vaccine uptake within low-income minority communities: evidence from the watts neighborhood health study.

BACKGROUND: The literature on disparities in COVID-19 vaccine uptake focuses primarily on the differences between White versus non-White individuals or differences by socioeconomic status. Much less is known about disparities in vaccine uptake within low-income, minority communities and its correlates. METHODS: This study investigates disparities in COVID-19 vaccination uptake within racial and ethnic minoritized communities with similar socioeconomic backgrounds and built environments, specifically focusing on Black-Hispanic disparities and disparities within the Hispanic community by country of origin. Data are analyzed from the fourth wave (June 2021- May 2022) of the Watts Neighborhood Health Study, a cohort study of public housing residents in south Los Angeles, CA. Linear probability models estimated the association between vaccine uptake and participants' race/ethnicity, sequentially adding controls for sociodemographic characteristics, health care access and insurance, prior infection, and attitudes towards COVID-19 vaccines. Differences in reasons for vaccination status by race/ethnicity were also tested. RESULTS: Mexican Hispanic and non-Mexican Hispanic participants were 31% points (95% CI: 0.21, 0.41, p < 0.001) and 44% points (95% CI: 0.32, 0.56, p < 0.001) more likely to be vaccinated than non-Hispanic Black participants, respectively. The disparity between Black and Hispanic participants was reduced by about 40% after controlling for attitudes towards COVID-19 vaccines. Among Hispanic participants, non-Mexican participants were 13% points (95% CI: 0.03, 0.24, p = 0.01) more likely to be vaccinated than Mexican participants, however, these differences were no longer significant after controlling for individual and household characteristics (ß = 0.04, 95% CI: -0.07, 0.15, p = 0.44). CONCLUSION: There are sizeable racial and ethnic COVID-19 vaccination disparities even within low-income and minoritized communities. Accounting for this heterogeneity and its correlates can be critically important for public health efforts to ensure vaccine equity.

Association of Place With Adolescent Obesity.

Importance: Despite strong evidence linking place and obesity risk, the extent to which this link is causal or reflects sorting into places is unclear. Objective: To examine the association of place with adolescents' obesity and explore potential causal pathways, such as shared environments and social contagion. Design, Setting, and Participants: This natural experiment study used the periodic reassignment of US military servicemembers to installations as a source of exogenous variation in exposure to difference places to estimate the association between place and obesity risk. The study analyzed data from the Military Teenagers Environments, Exercise, and Nutrition Study, a cohort of adolescents in military families recruited from 2013 through 2014 from 12 large military installations in the US and followed up until 2018. Individual fixed-effects models were estimated that examined whether adolescents' exposure to increasingly obesogenic places over time was associated with increases in body mass index (BMI) and probability of overweight or obesity. These data were analyzed from October 15, 2021, through March 10, 2023. Exposure: Adult obesity rate in military parent's assigned installation county was used as a summary measure of all place-specific obesogenic influences. Main Outcomes and Measures: Outcomes were BMI, overweight or obesity (BMI in the 85th percentile or higher), and obesity (BMI in the 95th percentile or higher). Time at installation residence and off installation residence were moderators capturing the degree of exposure to the county. County-level measures of food access, physical activity opportunities, and socioeconomic characteristics captured shared environments. Results: A cohort of 970 adolescents had a baseline mean age of 13.7 years and 512 were male (52.8%). A 5 percentage point-increase over time in the county obesity rate was associated with a 0.19 increase in adolescents' BMI (95% CI, 0.02-0.37) and a 0.02-unit increase in their probability of obesity (95% CI, 0-0.04). Shared environments did not explain these associations. These associations were stronger for adolescents with time at installation of 2 years or longer vs less than 2 years for BMI (0.359 vs. 0.046; P value for difference in association = .02) and for probability of overweight or obesity (0.058 vs. 0.007; P value for difference association = .02), and for adolescents who lived off installation vs on installation for BMI (0.414 vs. -0.025; P value for association = .01) and for probability of obesity (0.033 vs. -0.007; P value for association = .02). Conclusion and Relevance: In this study, the link between place and adolescents' obesity risk is not explained by selection or shared environments. The study findings suggest social contagion as a potential causal pathway.

Understanding drivers of micro-level disparities in childhood body mass index, overweight, and obesity within low-income, minority communities.

The focus of childhood obesity disparities has been mainly on macro-level disparities, such as, between lower versus higher socioeconomic groups. But, less is known about micro-level disparities, that is disparities within minority and low-income populations. The present study examines individual and family level predictors of micro-level obesity disparities. We analyze data on 497 parent-child dyads living in public housing communities in Watts, Los Angeles. Cross-sectional multivariable linear and logistic regression models were estimated to examine whether individual and family level factors predict children's BMI z-scores, overweight, and obesity in the sample overall and separately by child's gender and age group. Child characteristics of our study sample included mean age 10.9 years, 74.3% Hispanic, 25.7% Non-Hispanic Black, 53.1% female, 47.5% with household income below $10,000, 53.3% with overweight or obesity, and 34.6% with obesity. Parental BMI was the strongest and most consistent predictor of child zBMI, overweight, and obesity, even after controlling for parent's diet and activity behaviors and home environment. The parenting practice of limiting children's screentime was also protective of unhealthy BMI in younger children and females. Home environment, parental diet and activity behaviors, and parenting practices related to food and bedtime routines were not significant predictors. Overall, our findings show that there is considerable heterogeneity in child BMI, overweight, and obesity even within low-income communities with similar socioeconomic and built environments in their neighborhoods. Parental factors play an important role in explaining micro-level disparities and should be an integral part of obesity prevention strategies in low-income minority communities.

Impact of built, social, and economic environments on adolescent obesity and related health behaviors.

OBJECTIVE: This study aimed to estimate the effects of the built, social, and economic environments on adolescent obesity and related behaviors. METHODS: Exploiting quasi-exogenous variation in military families' geographic location, this study estimated intent-to-treat models of the association between the assigned installation's county environments and adolescents' (mean age 13.5 years) self-reported and model-corrected BMI, overweight or obesity status, and self-reported diet and exercise. Three indices for the built, social, and economic environments characterized county-level environments (higher value implies more advantageous environments) based on 19 indicators. Multivariate linear and logistic models were estimated on the full sample (N = 1111) and on subsamples with greater exposure based on time (n = 682) and off-installation residence (n = 604). RESULTS: Exposure to more advantageous built environments for more than 2 years was associated with lower probabilities of obesity (-0.18; 95% CI: -0.34 to -0.026) and overweight or obesity (-0.34; 95% CI: -0.56 to -0.12) and was associated with lower BMI z scores (-0.76; 95% CI: -1.45 to -0.02). Results for adolescents living off-installation were similar. More advantageous built environments were also associated with lower consumption of unhealthy foods, but not with physical activity. Social and economic environments were not associated with any outcomes. CONCLUSIONS: The built environment, but not social and economic environments, was a strong predictor of adolescents' BMI, overweight or obesity status, and eating behaviors.

Heterogeneity in place effects on health: The case of time preferences and adolescent obesity.

We leverage a natural experiment in combination with data on adolescents' time preferences to assess whether there is heterogeneity in place effects on adolescent obesity. We exploit the plausibly exogenous assignment of military servicemembers, and consequently their children, to different installations to identify place effects. Adolescents' time preferences are measured by a validated survey scale. Using the obesity rate in the assigned installation county as a summary measure of its obesity-related environments, we show that exposure to counties with higher obesity rates increases the likelihood of obesity among less patient adolescents but not among their more patient counterparts.

Heterogeneity in grocery shopping patterns among low-income minority women in public housing.

BACKGROUND: Public housing residents, who tend to be predominantly female and racial/ethnic minorities, are at a particularly high risk for chronic health conditions. Prior studies have suggested that a lack of access to healthy and affordable food may be an important barrier in public housing communities, but evidence is mixed on the association between the neighborhood food environment and dietary quality, suggesting the need to examine food access patterns in low-income, minority communities more deeply. The purpose of this study was to examine the variability in grocery shopping patterns, and the factors that predict them, among low-income minority women in public housing. METHODS: Interviewer-administered surveys and body composition measurements were collected in the Watts Neighborhood Health Study, an ongoing longitudinal cohort study of low-income urban public housing residents located in South Los Angeles. Descriptive analyses were conducted to understand the variation in grocery shopping patterns among women. Logistic and ordered logistic regression models were estimated to examine the association between resident characteristics and grocery shopping patterns. RESULTS: There was considerable variability in grocery shopping patterns, including the types of grocery stores accessed, distance travelled, frequency of shopping, and reasons behind grocery store choice. Grocery shopping patterns were associated with several participant characteristics, including race/ethnicity, working status, access to a car, income, and education. Hispanic participants were less likely to shop at a supermarket, travel further distances to shop, shop more frequently, and were more likely to prioritize price in their choice of primary grocery store than non-Hispanic Black women participants. CONCLUSIONS: There was considerable variability in grocery shopping patterns, even within this low-income, minority community despite access to the same neighborhood food environment. Convenience and quality, in addition to price, were priorities for choice of primary grocery store, and differences by race/ethnicity suggest that initiatives to improve the neighborhood food environment should consider quality of food, cultural factors, and availability of foods desired by the surrounding community, in addition to price and proximity of grocery stores.

Association of the Healthy, Hunger-Free Kids Act of 2010 With Body Mass Trajectories of Children in Low-Income Families.

Importance: Implemented in 2012, the Healthy, Hunger-Free Kids Act of 2010 (HHFKA) increased nutritional requirements of the National School Lunch Program (NSLP) to reverse the potential role of the NSLP in childhood obesity. Objective: To evaluate whether associations between the free or reduced-price NSLP and body mass growth differed after implementation of the HHFKA. Design, Setting, and Participants: This cohort study used data from 2 nationally representative cohorts of US kindergarteners sampled in 1998 to 1999 and 2010 to 2011 and followed up for 6 years, through grade 5, in the Early Childhood Longitudinal Study Kindergarten Class of 1998-1999 (ECLS-K:1999, in 2003-2004) and Kindergarten Class of 2010-2011 (ECLS-K:2011, in 2015-2016). In total, 5958 children were selected for analysis from low-income families eligible for the free or reduced-price NSLP (household income <185% of the federal poverty level) who attended public schools and had no missing data on free or reduced-price NSLP participation or on body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) at kindergarten or grades 1 and 5. Data were analyzed from January 1 to September 7, 2021. Exposures: Cross-cohort comparison of before vs after implementation of the HHFKA for free or reduced-price NSLP participation at kindergarten and grades 1 and 5. Main Outcomes and Measures: Body mass index difference (BMID) from obesity threshold was the difference in BMI units from the age- and sex-specific obesity thresholds (95th percentile) and is sensitive to change at high BMI. Multigroup models by cohort included weights to balance the distribution of the 2 cohorts across a wide range of covariates. A Wald test was used to assess whether associations differed between the cohorts. Results: In the final analysis, 3388 children in ECLS-K:1999 (1696 girls [50.1%]; mean [SD] age at baseline, 74.6 [4.3] months) and 2570 children in ECLS-K:2011 (1348 males [52.5%]; mean [SD] age at baseline, 73.6 [4.2] months) were included. The best fitting model for BMID change by free or reduced-price NSLP participation across the cohorts included fixed and time-varying associations. Before HHFKA implementation, grade 5 free or reduced-price NSLP participants had higher BMID, adjusted for their prior BMID trajectory, than nonparticipants (ß = 0.54; 95% CI, 0.27-0.81). After HHFKA implementation, this association was attenuated (ß = -0.07; 95% CI, -0.58 to 0.45), and grade 5 associations were different across cohorts (χ21 = 4.29, P = .04). Conclusions and Relevance: In this cohort study using cross-cohort comparisons, children from low-income families who participated in the free or reduced-price NSLP had a higher likelihood of progression to high BMI that was no longer observed after HHFKA implementation. This finding suggests that the HHFKA may have attenuated the previous association of the NSLP with child obesity disparities.

Food Choices in the Context of Globalizing Food Options among Adolescents in Rural Southern India.

Changes in food choice often accompany globalization and economic growth. These changes have not been well documented in rural settings and among young people. To advance research on food choice, we demonstrate adolescents' selection of local vs.non-local foods in a rural area of India where globalization is just reaching. A representative sample of 237 school-going adolescents in a village in Southern India completed a survey in 2019 to understand how adolescents decide among foods traditional to the area and foods arriving from other parts of the country and the world. Adolescents most frequently consumed local foods but also occasionally consumed non-local items. In hypothetical scenarios, 81% of the adolescents reported being most interested in substituting local foods with non-local foods if they were to have more money. Among the few who currently consumed non-local snacks and drinks, very few would be willing to replace them with local alternatives, particularly if they were to have more money (snacks: 10% and drinks: 5% respectively). Overall, adolescents were most interested in switching to non-local items when considering fruits, vegetables and snacks. As India faces the dual burden of undernutrition and overnutrition, understanding the changing food environment may help inform efforts to improve nutrition.

Assessing impacts of redeveloping public housing communities on obesity in low-income minority residents: Rationale, study design, and baseline data from the Watts Neighborhood Health Study.

INTRODUCTION: Obesogenic built- and social-environments in low-income and minority communities are often blamed for the higher rates of obesity in this population, but existing evidence is based largely on observational studies. This study leverages a natural experiment created by the redevelopment of a public housing community to examine the impact of major improvements to the housing, built, and social environments on obesity among residents. METHODS/DESIGN: The study design is a natural experiment where residents from the redeveloped community (treatment group) will be compared to those from a similar community (control group) in terms of their pre/post changes in primary outcomes using annual longitudinal data on a cohort of residents. Quasi-experimental variation in the timing of exposure to various redevelopment components within the treated community will be further leveraged within a stepped-wedge research design to assess the impact of the redevelopment components. Primary outcome measures include body mass index, overweight, and obese status. RESULTS: A cohort of 868 adults and 704 children (ages 2-17 years) was recruited during 2018-2019 with up to two waves of baseline data. At baseline, the prevalence of obesity (overweight or obesity) was 57.2% (81.3%) in adults and 33.1% (52.4%) among children, with no significant differences by treatment status. No differential trends in primary outcomes were observed by treatment status during the two years of baseline. DISCUSSION: This natural experiment study offers a unique opportunity to assess whether improvements to housing, built, and social environment in low-income minority communities can lead to reductions in obesity.

Predictive Utility of Alternate Measures of Physical Activity and Diet for Overweight and Obesity in Low-Income Minority Women.

PURPOSE: The purpose is to compare the predictive utility of alternate measures of diet and physical activity for overweight and obesity among low-income minority women. DESIGN: Cross-sectional analysis of baseline data from a cohort study. SETTING: Three public housing developments in South Los Angeles.Subjects: Adult women (N = 425). MEASURES: Primary outcome-weight status (normal BMI, overweight, or obese). Primary predictors- diet: 24-hour dietary recalls (Healthy Eating Index), dietary screener (intake of specific food groups), and single-item survey question (diet quality); physical activity: accelerometry (minutes/day of moderate-to-vigorous activity), short recall questionnaire (minutes/week of moderate and vigorous activity), and single-item questions (days per week did exercise; self-assessment of overall activity level). ANALYSIS: Multinomial logistic regression models, controlling for socio-demographic covariates. Models are built up starting with least resource-intensive measures of diet and physical activity (single items) and sequentially adding more resource-intensive measures. Model performance is assessed via information-based model selection indices. RESULTS: Adjusted relative risk for obesity for single-item measures ranged from .61 to .64 for diet (P < .01) and from .80 to .81 for physical activity (P <.05). The added value of resource-intensive measures was negligible for physical activity and at best small for diet. CONCLUSION: Single-item questions for diet and physical activity can provide valuable information about risk for overweight and obesity in low-income minority women when more resource-intensive assessments are infeasible.

Adolescent Time and Risk Preferences: Measurement, Determinants and Field Consequences.

We use experimental and survey measures to evaluate the time and risk preferences of nearly 500 adolescents aged 16-19 years old. We find that survey questions about time and risk preferences are weakly correlated with corresponding experiments in which participants trade-off monetary rewards. We find potentially substantial inter-generational transfer of time and risk preferences: parent time and risk preferences are strongly predictive of adolescent preferences for both survey and experimental measures. There are also interesting heterogeneities: girls are less risk seeking and more patient than boys when risk and time preferences are measured via surveys. Interestingly, the survey measures have more predictive power for field outcomes than the experimental measures. Higher patience as measured by the survey is significantly associated with lower body mass index (BMI), less time spent on sedentary activities, more time spent on physical activity and lower consumption of fast food and sweets.

The impact of state policies for school-based BMI/fitness assessments on children's BMI outcomes in rural versus urban schools: Evidence from a natural experiment.

Childhood obesity remains a public health crisis because of its alarming prevalence and potential for costly long-term health consequences, especially among rural children. Schools are considered natural loci for policies to combat obesity because children spend most of their active hours and consume a substantial share of their calories, at school. Recent state policy efforts have involved measuring children's BMI and/or fitness to notify parents or inform surveillance efforts, but the empirical evidence to date is far from definitive. This study leverages plausibly exogenous assignment of military families as a natural experiment to assess the association of such polices with children's BMI and obesogenic behaviors. The sample is stratified by urbanicity because of the likely differences in obesity prevalence and in environments necessary to support healthy lifestyles. Data were collected in 2013-2014 and analyzed in 2018-9. The policies were associated with lower odds of overweight (OR: 0.422; CI: 0.251-0.708) and at-risk of overweight (OR: 0.360; CI: 0.161-0.801) among children in rural, but not urban, schools. The policies were also associated with greater activity levels and less frequent intake of unhealthy foods, particularly among children attending rural schools. Results were robust to stratification based on urbanicity of the installation versus school, omission of family covariates, and other sensitivity analyses. Falsification checks on children's height, parental BMI outcomes, home food environments and neighborhood environments indicate findings are not driven by selection. BMI assessment policies were associated with children's BMI outcomes and health behaviors in rural, but not urban schools.

A novel approach to anthropometric assessment for geographically dispersed samples: A pilot study.

Measurements by trained personnel are the criterion standard for assessments of body mass index (BMI) and obesity. Yet, in-person measurements are less practical for studies of geographically dispersed samples. Recent advances in technology and the success of telehealth suggests that videoconferencing may be promising. We conducted a pilot study to examine the validity of videoconference-assisted measurements (VCAM) relative to in-person measurements by trained staff. We collected height, weight, percent body fat and waist circumference measurements using VCAM and staff measured in a convenience sample of 50 greater Los Angeles participants. We calculated relative standardized differences, and agreement between the two approaches using Pearson correlation and Bland-Altman plots. The small magnitude of differences (effect sizes <0.03), and high agreement suggested that the two approaches produce similar values. Thus, completing height and weight measurements through videoconference may be a valid and cost-effective approach, especially for geographically dispersed samples.

School Food and Beverage Availability and Children's Diet, Purchasing, and Obesity: Evidence From a Natural Experiment.

PURPOSE: Existing evidence on relationships between school food environments and children's in-school purchases, dietary behaviors, and body composition is based on observational studies that are vulnerable to residential selection bias. METHODS: This study leveraged exogenous variation in school environments generated by the natural experiment due to military parents' assignment to installations. We analyzed 1,010 child-wave observations from the Military Teenagers Environments, Exercise, and Nutrition Study collected during 2013-2015. Using multiple linear and logistic regression, we examined whether the number of competitive food and beverage (CF&B) items available for purchase in school, overall and by type (unhealthy, healthy, neutral), was associated with in-school food purchases, dietary behaviors, and body mass index (BMI) outcomes. Covariates included child and family characteristics and the healthiness of the home food environment. RESULTS: Unhealthy item availability was positively associated with purchasing any sweets (adjusted odds ratio [AOR], 1.30; p < .01), snacks (AOR, 1.23; p < .01), and sugar-sweetened beverages (AOR, 1.19; p = .01). However, there were no significant associations with overall food and beverage intake (e.g., sweets, soda) nor BMI outcomes. The home food environment was significantly associated with all outcomes. CONCLUSIONS: Access to unhealthy CF&B items may influence in-school purchases but does not appear to influence overall dietary behaviors and BMI outcomes. Substitution of caloric intake across locations within versus outside of school may play a role in explaining why purchases were associated with unhealthy CF&B availability but overall diet and downstream BMI were not.

Childhood Self-Control and Adolescent Obesity: Evidence from Longitudinal Data on a National Cohort.

BACKGROUND: Whether self-control at school entry and changes in self-control in the early school years are predictive of BMI change and obesity onset over the next 8 years using longitudinal data on a nationally representative sample of US children. METHODS: Data from the Early Childhood Longitudinal Study-Kindergarten Class 1998 were analyzed. The analysis sample included 7060 children with data from kindergarten (mean age = 6 years) until eighth grade (mean age = 14 years). Self-control was assessed using teacher-reported scales. Child BMI and obese status (BMI ≥95th percentile for age and gender) were computed from height and weight measurements. Weighted linear and logistic regression models were estimated, adjusting for child's cognitive ability and a rich set of child and family covariates. RESULTS: High self-control in kindergarten was associated with lesser BMI increase (p < 0.05) and 43% lower odds (adjusted OR [AOR] = 0.57, 95% confidence interval [CI]: 0.38-0.86) of new onset obesity over the subsequent 8 years. The beneficial effect of high self-control in kindergarten emerged between fifth and eighth grade. Among children with low self-control in kindergarten, increase in self-control between kindergarten and fifth grade was associated with a 1.42 kg/m2 (95% CI: -2.82 to -0.02) lesser increase in BMI and 66% lower odds of new obesity onset (AOR = 0.34; 95% CI: 0.14-0.83), between kindergarten and eighth grade. CONCLUSIONS: Low self-control at school entry is an important risk factor for unhealthy BMI increase during the transition to adolescence. Increase in self-control in the early school years may prevent unhealthy BMI increase and obesity in adolescence.

Neighborhood Environments and Physical Activity: A Longitudinal Study of Adolescents in a Natural Experiment.

INTRODUCTION: Experimental and quasi-experimental evidence on the relationship between adolescents' physical activity and their physical activity environments is scarce. This study provides natural experimental evidence using within-person longitudinal variation in physical activity environments resulting from the compulsory re-assignment of military families to new installations, termed permanent changes of station. METHODS: Adolescents in Army families (N=749) reported usual weekly minutes of moderate and vigorous physical activity in 2013-2015. Objective measures of the physical activity environment, including the number of fitness and recreation facilities within 2 miles, were constructed for adolescents' neighborhoods using GIS methods. In 2017, individual-level fixed-effects models with and without a comparison group estimated the relationship between usual weekly minutes of physical activity and physical activity environments among permanent changes of station movers using within-person variation. RESULTS: Increases in opportunities for physical activity were significantly and positively associated with increases in total (p<0.05) and vigorous physical activity (p<0.05) among adolescents who experienced permanent changes of station moves. The relationships were statistically significant for permanent changes of station movers living off-installation (p<0.05) and hence subject to greater variation in physical activity environments and those with more time to adjust to their new environments (p<0.05). Significant findings persisted when broader measures of physical activity environments were utilized. CONCLUSIONS: The decline in physical activity and alarming obesity levels during adolescence suggest that this age may represent an important opportunity to address the obesity epidemic. This study provides evidence that increasing opportunities for physical activity may be an important pathway to improving their levels of physical activity and, consequently, obesity.

Assessing Social Contagion in Body Mass Index, Overweight, and Obesity Using a Natural Experiment.

Importance: Little is known about whether the substantial clustering of obesity and overweight within social and geographic networks results from causal pathways, such as social contagion and shared environments, or from self-selection. Objectives: This study aimed to determine whether exposure to communities with higher rates of obesity increases the body mass index (BMI) of individuals, calculated as weight in kilograms divided by height in meters squared, and their risk of being overweight or obese, and whether social contagion, shared environments, or self-selection can account for identified differences. Design, Setting, and Participants: This natural experiment study used the routine assignment of military service members to installations as a source of exogenous variation in exposure to communities with higher vs lower rates of obesity. The study, which used data collected by the Military Teenagers' Environments, Exercise, and Nutrition Study, examined families from 38 military installations around the United States to determine if individuals had higher BMI and greater odds of overweight and obesity when assigned to installations in counties with higher rates of obesity. The study also examined if the relationship persisted after controlling for shared built environments. The participants included 1 parent and 1 child aged 12 or 13 years from 1519 families of Army-enlisted personnel. Data analysis was completed from November 2016 to October 2017. Exposures: Adult obesity rate in the county where the assigned installation of the service member was located. Time at installation and location of residence (on-installation vs off-installation) were used to measure the degree of exposure. Main Outcomes and Measures: For parents, outcomes were BMI, overweight/obesity (BMI, ≥25) and obesity (BMI, ≥30). For children, outcomes were BMI z score, overweight/obesity (BMI percentile for age and sex, ≥85), and obesity (BMI percentile for age and sex, ≥95). These outcomes were based on self-reports for parents, self-reports and parent reports for all children, and anthropometric measurements for a subsample of children. Results: Members of 1519 families participated, including 1314 adults (of whom 740, or 56%, were fathers) and 1111 children (of whom 576, or 52%, were boys); anthropometric measurements were performed on 458 children. The sample was 40% white, 22% black, 24% Hispanic, and 14% other races/ethnicities. A 1-percentage point higher county obesity rate was associated with a higher BMI (a difference of 0.08; 95% CI, 0.02-0.13) and greater odds of obesity (adjusted odds ratio [aOR], 1.05; 95% CI, 1.02-1.08) in parents, and a higher BMI z score (0.01; 95% CI, 0.003-0.02) and greater odds of overweight/obesity (aOR, 1.04; 95% CI, 1.01-1.06) in children. The evidence supported stronger associations among families with more time at installation and off-installation residence. Associations persisted even after controlling for shared built environments. Conclusions and Relevance: Exposure to counties with higher rates of obesity was associated with higher BMI and higher odds of overweight and/or obesity in parents and children. There was no evidence to support self-selection or shared built environments as possible explanations, which suggests the presence of social contagion in obesity.

Entrenched obesity in childhood: findings from a national cohort study.

PURPOSE: Given the high levels of obesity among U.S. children, we examine whether obesity in childhood is a passing phenomenon or remains entrenched into adolescence. METHODS: Data are from the prospective nationally representative Early Childhood Longitudinal Study, Kindergarten Class of 1998-1999 (analytic sample = 6600). Anthropometrics were measured six times during 1998-2007. Overweight and obesity were defined using CDC cut-points. Entrenched obesity was defined as obesity between ages 5-9 coupled with persistent obesity at ages 11 and 14. RESULTS: Almost 30% of children experienced obesity at some point between ages 5.6 and 14.1 years; 63% of children who ever had obesity between ages 5.6 and 9.1 and 72% of those who had obesity at kindergarten entry experienced entrenched obesity. Children with severe obesity in kindergarten or who had obesity at more than 1 year during early elementary were very likely to experience obesity through age 14, regardless of their sex, race, or socioeconomic backgrounds. CONCLUSIONS: Prevention should focus on early childhood, as obesity at school entry is not often a passing phenomenon. Even one timepoint of obesity measured during the early elementary school years may be an indicator of risk for long-term obesity.