While the strong upward trend in rates of obesity and overweight is a national phenomenon, the South appears to have been more affected than other regions. Prevalence estimates of obesity, collected through the Centers for Disease Control and Prevention’s (CDC) Behavioral Risk Factor Surveillance System (BRFSS), show that in the year 2005, all three States with obesity rates (defined as body mass index (BMI) > 30) above 30 percent were in the South: Louisiana, Mississippi, and West Virginia. All other Southern States, with the exception of Delaware, Florida, Maryland, and Virginia, had rates of obesity in the range of 25 to 29 percent. No Southern States had obesity rates below 20 percent.
High levels of poverty, relative to national averages, characterize many States in the South. In 2004, when the national poverty rate was 12.7 percent, Alabama, Kentucky, Texas, and West Virginia reported rates over 16 percent while poverty rates in Mississippi and Louisiana exceeded 19 percent. Data from the 2005 CDC BRFSS show that most Southern States report rates of recommended fruit and vegetable consumption below the national average (which in itself was not high). In addition, many Southern States report a percentage of current smokers above the national average. The objective of this project was to test regional differences in BMI, diet quality, and the probability of being obese, with a focus on the South. A major question of interest was whether differences in BMI across regions and the probability of being obese can be explained by the demographic characteristics of the region or whether, even when these factors are controlled, there still is a statistically significant increase in probability that those living in the South will be obese. The link between BMI and diet quality was also explored.
The National Center for Health Statistics’ National Health and Nutrition Examination Study (NHANES) for 1999-2002 provides information about individuals’ consumption of foods and nutrients, as well as body measurements (height, weight, and BMI) and information about demographic and socioeconomic characteristics. The NHANES 1999-2002 contains the 18-item Food Security Survey Module (FSSM), which has been shown to be a stable, robust, and reliable measurement tool. The NHANES 1999-2002 Food Security data are released in four categories: food secure (FS), marginally food secure (MFS), food insecure without hunger (FIWOH), and food insecure with hunger (FIWH). Because adults were the focus of this analysis, the adult measure rather than the household measure was used.
For the 1999-2002 NHANES, individuals’ dietary intakes were collected through an interviewer-administered 24-hour dietary recall method. Following guidelines and sample statistical code provided by USDA’s Center for Nutrition Policy and Promotion, the information in the dietary recall can be used to construct the Healthy Eating Index-2005 (HEI-2005), a measure of diet quality.
Geographic variables, such as State or census region, are not released in the public NHANES data. The CDC does allow researchers access to unreleased data for valid research purposes, however, and access to confidential geographic variables (census region and State) was provided for this project following approval of a proposal for such access.
The analytical sample for this work is the subset of individuals who participated in the Mobile Examination Center (MEC). Nonelderly adults who were not pregnant or lactating were the focus of this research, so those individuals 18-60 years of age were included. Because prior research has found differences in obesity patterns among men and women, they were examined separately (women, n=3,424; men, n=3,052). Multivariate linear regression analyses were used to examine the relationships between geographic region and BMI, obesity, and diet quality while controlling for age, race-ethnicity, education, income, and other possible covariates, such as food security status, self-reported activity level, smoking status, and alcohol consumption patterns. To account for survey design, survey procedures in Statistical Analysis Software (SAS) were used.
When data were analyzed across the four census regions, no significant differences in BMI or obesity were found for either women or men. Women in the South had a significantly lower diet quality than women in either the West or Northeast. Men in both the South and the Midwest had a significantly worse diet quality than men in the West. Lack of significant difference for the South in terms of obesity and BMI was not expected, given the results from the BRFSS reports. Two possible explanations for the lack of significance were explored. The BRFSS data are self-reported. Hence, respondents in the Southern region may have reported relatively heavier weights (or shorter heights) than did respondents in the other census regions compared with their actual heights and weights. As the NHANES data include self-reported heights and weights, to test the possibility of different regional biases in self-reports, the self-reported heights and weights were used to construct a BMI measure. No significant difference in self-reporting bias was found across regions.
Another possibility for the difference between these results and the BRFSS reports is that the census region of the South includes a number of States, such as Florida and Virginia, that do not have higher-than-average rates of obesity. Accordingly, the South was split into two regions, the Deep South (Alabama, Arkansas, Georgia, Mississippi, South Carolina, and Tennessee) and the “other South.” For the Deep South, mean BMI for women was 29.2 when no covariates were considered, which was significantly higher than the “other South” and the West, with similar results for obesity. For men, there were no significant differences in BMI or the probability of obesity for the Deep South compared with other regions. When demographic covariates were included in regression analyses, the difference in BMI and obesity for women in the Deep South disappeared. Low-income women and Black women were found to have higher BMI than higher income women and White women. The South is a region with lower-than-average income and higher-than-average minority population; therefore, these factors most likely contribute to the reportedly higher-than-average rates of obesity for many Deep South States. Although HEI-2005 was found to be inversely related to BMI and the probability of obesity for both men and women, the effect was small. The lower-than-average diet quality in the South would thus not appear to make a large contribution to the region’s obesity rates. Food insecurity levels did not relate strongly to obesity or BMI for women. Men who are FIWOH were found to have a lower BMI than fully food-secure men.
Direct inquiries about this study to the Project Contact listed above.