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“We want to understand which strategies are most effective within the context of a specific neighborhood.” -Dr. May Wang
CHILDHOOD OBESITY HAS BEEN VIEWED AS A PUBLIC HEALTH CRISIS since at least the early 2000s in the U.S., with the percentage of obese children having more than tripled since the 1970s. In response, public health departments, private foundations, schools, community-based organizations and others have implemented wide-ranging strategies — particularly in low-income communities, where access to healthy foods and places to exercise tends to be limited. In Los Angeles County, efforts have been undertaken to improve the food environment by introducing farmers markets and working with corner stores to increase healthy options; improving physical activity resources through investments in safer parks; and providing nutrition education and breastfeeding promotion for families, to name a few. Taken as a whole, these interventions appear to be making some headway. For example, among L.A. County children ages 3-4 who are participants in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) — an important subgroup given that WIC serves a low-income population, and because of the strong connection between obesity early in life and obesity in adulthood — obesity rates increased from 2003 to 2009, then began to decline.
But knowing exactly which interventions brought about the positive change — and as a result, where to continue investing finite resources — is another question. Moreover, strategies that succeed in one neighborhood might be less successful in another because of a host of environmental, demographic and cultural factors. “In looking at our data it became very clear that we have families in census tracts right next to each other with very different obesity rates — one community where the trajectory was going up right next to another where it was going down, for reasons that weren’t clear,” says Dr. Shannon Whaley, director of research and evaluation at Public Health Foundation Enterprises WIC (PHFE-WIC), which provides services in Los Angeles, Orange and San Bernardino counties as the nation’s largest local WIC agency. “Up to now, no study that I’m aware of has looked at the interplay between community-level environmental issues and early childhood obesity rates.”
In that sense, a Fielding School-led research group — in partnership with PHFEWIC, the Los Angeles County Department of Public Health and other institutions — is breaking new ground through an ambitious five-year project funded in 2013 by the National Institutes of Health. Taking advantage of the extensive administrative database maintained by PHFE-WIC and the high quality of data as reported by co-investigator Dr. Kate Crespi of FSPH’s Department of Biostatistics, the Early Childhood Obesity Systems Science Study (ECOSyS) is examining the impact of major obesity-related programs and policies in L.A. County since 2003 on preschool-aged WIC participants.
“We want to understand which strategies are most effective within the context of a specific neighborhood,” says Dr. May Wang, professor in FSPH’s Department of Community Health Sciences and one of the study’s two principal investigators. “Ultimately, our goal is to create a tool that will allow agencies to identify the most effective strategy for addressing childhood obesity in the communities they serve.”
Wang notes that ECOSyS is among the first studies to evaluate community-based public health interventions employing methodology from the field of systems science, which uses computer modeling to assess the impact of interventions in a way that considers the complex interactions that occur rather than analyzing individual strategies without consideration of the myriad factors that influence the effectiveness of an intervention.
“ECOSyS is providing us the opportunity to rethink how we evaluate public health programs and policies,” explains the study’s other principal investigator, Dr. Michael Prelip, professor in FSPH’s Department of Community Health Sciences and the school’s associate dean for practice across the life course. “Rather than examine one program or policy at a time to see its impact, with systems science we can examine a collection of programs and policies all at once to determine their impact on obesity among the 2-5 year old population.”
Fifty-five percent of L.A. County children under 5 are enrolled in the WIC program, which serves pregnant and postpartum women, infants and children up to age 5 who are low income (at or below 185 percent of the federal poverty level) and at nutritional risk. WIC provides vouchers for nutritious foods, nutrition education, breastfeeding support, and referrals to health care and other services.
PHFE-WIC has maintained a sophisticated database for L.A. County since 2003 thanks to partnerships with the California Department of Public Health WIC Program and the six other local agency WIC programs providing services in Los Angeles County. This work has been supported by the nonprofit child advocacy organization First 5 LA. Along with demographic information and records tracking each child’s height, weight and body mass index over time, PHFE-WIC’s database includes responses to the triennial L.A. County WIC Survey of participants on topics such as food and sugar-sweetened beverage intake, breastfeeding practices, and household food security. Information on each WIC family is also geo-coded by census tract, allowing the FSPH-led team to look at trends at the neighborhood level. “This is a unique resource — most WIC programs don’t collect or maintain data in a way that can be analyzed by researchers, but PHFE-WIC had the forethought to do that,” says Wang, who has worked closely with the agency since joining the Fielding School faculty in 2008.
To determine which intervention strategies are most effective in a given community, the FSPH researchers are applying a form of systems science known as agent-based modeling. “Agent-based modeling creates a virtual laboratory using computer models that incorporate the best available evidence about what governs individual behaviors and how these behaviors are influenced by our past behaviors, people around us and where we live,” explains Roch Nianogo (PhD ’17), who has contributed to the modeling as a graduate student researcher. “This allows researchers and policymakers to run simulated experiments to evaluate the impact of potential interventions through ‘what-if’ scenarios so that we can avoid wasteful spending on interventions that will not prove successful.”
Wang notes that because systems science is relatively new and not typically taught in schools of public health, the study has led to unlikely working partnerships between computer programmers and public health researchers. The FSPH research team brought in Dr. Nathaniel Osgood of the University of Saskatchewan in Canada, a faculty member in both computer science and community health, to help bridge the divide as a consultant. “We paired our students with his computer science PhD students,” Wang says. “It took a lot of teaching on both sides to understand each other’s work, but it has been very successful.”
“It is very rare that a complex issue like childhood obesity is going to be amenable to just one discipline,” says Dr. Onyebuchi Arah, FSPH professor of epidemiology, who has contributed to the statistical modeling as a study co-investigator. “By drawing on the tools of computer science, biostatistics, epidemiology and community health sciences, we can accomplish so much more.”
Traditionally, public health strategies to combat obesity relied largely on education, but beginning in the early 2000s, the focus shifted to the neighborhood environment, notes Wang, who led one of the earliest major studies on the impact of neighborhood food environments on obesity in California. Since that time, a number of interventions have been implemented in Los Angeles, and the FSPH-led study has cast a wide net in the strategies being evaluated. These include investments by The California Endowment and Kaiser Permanente in changing the neighborhood and school food environments of low-income communities; community transformation grants funded by the U.S. Centers for Disease Control and Prevention; and First 5 LA’s programs promoting breastfeeding and healthy eating among preschool-aged children.
Fielding School research in the early 2000s by the late Dr. Gail Harrison and one of her students, Dena Herman (MPH ’95, PhD ’02), now an adjunct associate professor in the Fielding School’s Department of Community Health Sciences, inspired another major change in the food environment for children under 5. Harrison and Herman found that providing WIC recipients with vouchers for fruits and vegetables resulted in sustainable increases in consumption, leading to a revamping of the WIC food package in 2009 to include fruits and vegetables. The L.A. County Department of Public Health, meanwhile, has introduced farmers markets to improve the food environment of low-income areas, worked with corner stores and faith-based organizations to emphasize healthy food offerings, and encouraged the development of purchasing cooperatives to enable small store owners to negotiate lower prices for healthy items, among other strategies.
The stakes for these strategies are high. Obesity early in life tracks into adulthood, Wang notes, with overweight preschool-aged children at much greater risk of becoming obese adults than non-overweight children. Being able to better predict the impact of proposed strategies on early childhood obesity in given communities would allow public and private dollars to be invested with more precision.
“We know that the older people get, the more their habits become ingrained,” says Dr. Tony Kuo, adjunct associate professor of epidemiology at the Fielding School and acting director of the Division of Chronic Disease and Injury Prevention for the L.A. County Department of Public Health. “By understanding the best ways to steer parents toward instilling healthy habits in their young children, we have a chance to set those families on a healthy course for the rest of their lives.”