May C. Wang

Socioeconomic and food-related physical characteristics of the neighbourhood environment are associated with body mass index

Objective: To determine whether socioeconomic and food-related physical characteristics of the neighbourhood are associated with body mass index (BMI; kg/m2) independently of individual-level sociodemographic and behavioural characteristics. Design and methods: Observational study using (1) individual-level data previously gathered in five cross-sectional surveys conducted by the Stanford Heart Disease Prevention Program between 1979 and 1990 and (2) neighbourhood-level data from (a) the census to describe socioeconomic characteristics and (b) data obtained from government and commercial sources to describe exposure to different types of retail food stores as measured by store proximity, and count of stores per square mile. Data were analysed using multilevel modelling procedures. The setting was 82 neighbourhoods in agricultural regions of California. Participants: 7595 adults, aged 25–74 years. Results: After adjusting for age, gender, ethnicity, individual-level socioeconomic status, smoking, physical activity and nutrition knowledge, it was found that (1) adults who lived in low socioeconomic neighbourhoods had a higher mean BMI than adults who lived in high socioeconomic neighbourhoods; (2) higher neighbourhood density of small grocery stores was associated with higher BMI among women; and (3) closer proximity to chain supermarkets was associated with higher BMI among women. Conclusion: Living in low socioeconomic neighbourhoods, and in environments where healthy food is not readily available, is found to be associated with increased obesity risk. Unlike other studies which examined populations in other parts of the US, a positive association between living close to supermarkets and reduced obesity risk was not found in this study. A better understanding of the mechanisms by which neighbourhood physical characteristics influence obesity risk is needed.

ETHNIC ISSUES IN THE EPIDEMIOLOGY OF CHILDHOOD OBESITY

Childhood obesity may be seen as a marker for high-risk dietary and physical inactivity practices. Recent increases in the prevalence of overweight and obesity among American children are not limited to one age, gender, or ethnic group, which suggests that unique behaviors of the members of various racial or ethnic subgroups of the population are unlikely to be the major contributing factors. Rather, it seems that environmental changes promoting increased energy intake and decreased energy output are occurring and have widespread impact on children from various backgrounds. Although no ethnic group is immune from the current shift in energy balance, differential rates of overweight seem to exist among ethnic groups. National probability samples of African-American, Hispanic, and white children in the United States provide clear evidence that white children are at lower risk for childhood overweight than are African-American or Hispanic children. Of concern is the lack of national data on the prevalence of overweight and obesity for Native-American and Asian-American groups. Also of concern is the aggregation of racial and ethnic subgroups, which may render prevalence rates meaningless. This possibility is clearly true with some surveys of weight status that combine diverse populations, such as Asians and Pacific Islanders, into one group. The high rates of obesity in African-American, Hispanic, and Native-American children are of concern. Although parental SES is associated inversely with childhood obesity among whites, higher SES does not seem to protect African-American and Hispanic children against obesity. In these groups, childhood obesity does not seem to be associated significantly with parental income and education. Health consequences of childhood obesity include a higher prevalence of type 2 diabetes and an increased risk for adverse levels of lipids, lipoproteins, and blood pressure. The effects of recently reported unprecedented levels of childhood overweight on subsequent risk for obesity in middle age are not known until future longitudinal data can be collected. It seems likely, however, that future health consequences of current early and severe childhood obesity will be staggering. Funding for adult follow-up of longitudinal studies of high-risk African American, Hispanic, and Native-American children is needed urgently to provide information on the long-term effects of childhood obesity. Halting the obesity epidemic is a formidable task, but the success in recent decades of drastically reducing childhood undernutrition offers hope and should spur similar action and leadership efforts. Promotion of efforts to reduce excess caloric intake with efforts to increase energy expenditure should receive paramount attention in the design of health programs. Given the relatively few published obesity-prevention and treatment studies that are designed to address specific cultural issues, it is important to promote the development of culturally appropriate intervention strategies that are shown to be effective among youth of diverse backgrounds. Although the dietary and activity goals will be similar, parental, family, and community messages and techniques grounded in cultural traditions and norms will be different for each ethnic group. This approach is crucial in the United States, a country with an increasingly diverse population.

The neighborhood food environment: sources of historical data on retail food stores

With the rapidly increasing prevalence of obesity in the United States, and the minimal success of education-based interventions, there is growing interest in understanding the role of the neighborhood food environment in determining dietary behavior. This study, as part of a larger study, identifies historical data on retail food stores, evaluates strengths and limitations of the data for research, and assesses the comparability of historical retail food store data from a government and a commercial source.Five government and commercial listings of retail food stores were identified. The California State Board of Equalization (SBOE) database was selected and then compared to telephone business directory listings. The Spearmans correlation coefficient was used to assess the congruency of food store counts per census tract between the SBOE and telephone business directory databases. The setting was four cities in Northern California, 1979–1990.The SBOE and telephone business directory databases listed 127 and 351 retail food stores, respectively. The SBOE listed 36 stores not listed by the telephone business directories, while the telephone business directories listed 260 stores not listed by the SBOE. Spearmans correlation coefficients between estimates of stores per census tract made from the SBOE listings and those made from the telephone business directory listings were approximately 0.5 (p < .0001) for the types of stores studied (chain supermarkets, small grocery stores, and chain convenience markets). We conclude that, depending on the specific aims of the study, caution and considerable effort must be exercised in using and applying historical data on retail food stores.

Changes in neighbourhood food store environment, food behaviour and body mass index, 1981-1990

OBJECTIVE This paper examines trends in the neighbourhood food store environment (defined by the number and geographic density of food stores of each type in a neighbourhood), and in food consumption behaviour and overweight risk of 5779 men and women. DESIGN The study used data gathered by the Stanford Heart Disease Prevention Program in four cross-sectional surveys conducted from 1981 to 1990. SETTING Four mid-sized cities in agricultural regions of California. SUBJECTS In total, 3154 women and 2625 men, aged 25-74 years. RESULTS From 1981 to 1990, there were large increases in the number and density of neighbourhood stores selling sweets, pizza stores, small grocery stores and fast-food restaurants. During this period, the percentage of women and men who adopted healthy food behaviours increased but so did the percentage who adopted less healthy food behaviours. The percentage who were obese increased by 28% in women and 24% in men. CONCLUSION Findings point to increases in neighbourhood food stores that generally offer mostly unhealthy foods, and also to the importance of examining other food pattern changes that may have a substantial impact on obesity, such as large increases in portion sizes during the 1980s.

Exposure to a comprehensive school intervention increases vegetable consumption.

PURPOSE The current epidemic of childhood overweight has launched a variety of school-based efforts to address the issue. This study reports on the first 2 years of a 3-year evaluation of one school districts comprehensive intervention to transform school foodservices and dining experiences, offer cooking and gardening programs, and integrate nutrition and food systems concepts into the academic curriculum. METHODS This 3-year prospective study enrolled 327 4th and 5th graders in a mid-sized school district in California, and followed them into middle school. Intervention exposure was determined through interviews with school staff and student surveys. Student knowledge and attitudes were assessed annually by questionnaire, and student behavior was assessed annually by 3-day food diary. Household information was gathered by parent questionnaire. Changes in knowledge, attitudes, and behavior were compared by level of intervention exposure using analysis of covariance; pairwise differences were evaluated using Bonferronis test at a procedure-wise error rate of 5%. RESULTS After controlling for family sociodemographic background, students most exposed to the intervention increased their consumption of fruits and vegetables by nearly 0.5 cups (one standard serving), whereas students least exposed decreased their consumption by 0.3 cups (p < .05). Students most exposed to the programming also showed a significantly greater increase in preference for fruit and green leafy vegetables, compared to students least exposed to the programming (p < .05). CONCLUSIONS Future research is needed to better understand the relative importance of the different components of such a program, and their cost-benefits as well as health impacts.

Influence of Pre-adolescent Diet on Quantitative Ultrasound Measurements of the Calcaneus in Young Adult Women

Abstract: Nongenetic determinants of quantitative ultrasound (QUS) properties of the bone remain to be identified. The purpose of this study was to determine relationships between early adolescent diet and QUS bone measurements taken in young adulthood. Subjects were participants in the 10-year longitudinal National Heart, Lung, and Blood Institute Growth and Health Study (NGHS). QUS parameters measured at the calcaneus in a convenience subsample of 63 18- to 19-year-old black and white women were correlated with dietary data collected when the subjects were aged 9-11 years. We hypothesized that pre-adolescent intake of calcium, magnesium, vitamin C and protein, nutrients known to be associated with bone development, would be associated with QUS measurements in young women. Stepwise multiple regression analysis, controlling for race, height and weight, demonstrated that pre-adolescent intake of calcium and magnesium were positively related to QUS parameters (calcium with broadband ultrasound attenuation, and magnesium with speed of sound and bone velocity). Our findings suggest that pre-adolescent diet may be associated with bone properties as measured by ultrasound. Further investigations of this relationship may yield a deeper understanding of the impact of diet on skeletal development. The small size of the convenience sample used for the analysis precludes stronger inferences at this time.

Validity of child anthropometric measurements in the Special Supplemental Nutrition Program for Women, Infants, and Children.

Introduction:The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) serves 50% of infants and 25% of preschool-aged children in the United States and collects height and weight measurements from eligible children every 6 mo, making WIC data a valuable resource for studying childhood growth and obesity. We assessed the accuracy of measurements collected by WIC staff by comparing them to “gold standard” measurements collected by trained research staff.Results:Intraclass correlation coefficients (ICCs) measuring agreement between WIC and research protocol measurements for height, weight, and BMI were 0.96, 0.99, and 0.93, respectively. Although WIC measurements overestimated height by 0.6 cm and weight by 0.05 kg on average, BMI was underestimated by only 0.15 kg/m2 on average. WIC BMI percentiles classified children as overweight/obese vs. underweight/normal with 86% sensitivity and 92% specificity.Discussion:We conclude that height, weight, and BMI measurements of children aged 2–5 y collected by trained WIC staff are sufficiently accurate for monitoring and research purposes.Methods:At seven WIC clinics in southern California, 287 children aged 2–5 y measured for height and weight by WIC staff using WIC standard protocol were remeasured by research staff using a research protocol (duplicate measurements with shoes and outerwear removed were taken by trained personnel).

Neighbourhood environment as a predictor of television watching among girls

Background: Television watching, a sedentary activity, has been associated with overweight in children. While the family environment is known to influence television watching, little is known about the influence of the neighbourhood environment. This study is an exploratory examination of the association of socioeconomic characteristics of the neighbourhood environment with television watching among 9–10 year old girls. Methods: Data collected by the Berkeley site of the National Heart, Lung and Blood Institute Growth and Health Study (NGHS) in 1987–8 from 787 girls who had a complete set of measurements relevant to the analysis were used. These measures included parental education, household income, race and weekly hours spent watching television. Addresses of the girls were geocoded and the median household income for the census tracts in which they lived was used to indicate neighbourhood socioeconomic characteristics. Multilevel modelling procedures were used to estimate fixed effect coefficients for individual and neighbourhood level variables. Results: Living in high income areas was associated with less television watching, a finding that held even when controlling for parental education, household income and race. Race and parental education were also associated with television watching. Conclusion: Television watching among girls was associated not only with the socioeconomic characteristics of their households, but also of their neighbourhoods. Future studies should explore the mechanisms that mediate this relation and determine if these results are generalisable to other populations.

Validity of the body mass index as an indicator of adiposity in an ethnically diverse population of youths

The primary objective was to investigate the influences of ethnicity and pubertal stage on the ability of body mass index (BMI) to rank adiposity in a cohort of 402 Asian, African, Hispanic, and White Americans, aged 9–25 years. BMI was calculated from measured weight and height. Body composition and pubertal stage were determined by dual energy x‐ray absorptiometry and self‐rating, respectively. Multiple linear regression models with BMI, ethnicity, puberty, and age as explanatory variables were used to determine if ethnicity and pubertal stage modify the ability of BMI to predict percent of body weight that is fat (%BF). Spearmans correlation coefficients of BMI with %BF were also estimated. Both ethnicity and pubertal stage interacted with BMI. The correlation between BMI and %BF (r) was much higher in females (r = 0.72, P < 0.001) than in males (r = 0.15, NS). Among females, correlations did not vary much by pubertal stage, but tended to be higher in Blacks. Among males, correlations tended to be low during mid‐puberty. However, a high correlation between BMI and lean body mass (LBM) was consistently observed in mid‐pubertal males across all ethnic groups. Stratification by quartile of BMI showed that the correlation was >0 (P < .05) only in the highest quartile. Thus, in an ethnically diverse cohort of 9–25 year olds, the correlation between BMI and %BF is poor in the lower quartiles of BMI. In comparison, LBM correlates better with BMI than %BF in the lower quartiles of BMI.

The New Food Package and Breastfeeding Outcomes Among Women, Infants, and Children Participants in Los Angeles County

OBJECTIVES We assessed the effect of the new Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) food package, implemented in October 2009, on breastfeeding outcomes among a predominately Latina sample of WIC participants in Los Angeles County, California. METHODS We used data from 5020 WIC participants who were interviewed in a series of repeated cross-sectional surveys conducted in 2005, 2008, and 2011. Participants were randomly selected from Los Angeles County residents who received WIC services during those years. RESULTS Consistent with the WIC population in Los Angeles, participants were mostly Latina and had low levels of income and education; more than half were foreign-born. We found small but significant increases from pre- to postimplementation of the new WIC food package in prevalence of prenatal intention to breastfeed and breastfeeding initiation, but no changes in any breastfeeding at 3 and 6 months. The prevalence of exclusive breastfeeding at 3 and 6 months roughly doubled, an increase that remained large and significant after adjustment for other factors. CONCLUSIONS The new food package can improve breastfeeding outcomes in a population at high risk for negative breastfeeding outcomes.