摘要：Objectives. To better understand health disparities, we compared US weight gain trends across sociodemographic groups between 1986 and 2002. Methods. We analyzed mean and 80th-percentile body mass index (BMI), calculated from self-reported weight and height, for subpopulations defined by education, relative income, race/ethnicity, and gender. Data were from the Behavioral Risk Factor Surveillance System, a random-digit-dialed telephone survey (total sample=1.88 million adult respondents). Results. Each sociodemographic group experienced generally similar weight gains. We found no statistically significant difference in increase in mean BMI by educational attainment, except that individuals with a college degree gained less weight than did others. The lowest-income group gained as much weight on average as the highest-income group, but lowest-income heavier individuals (80th percentile of BMI) gained weight faster than highest-income heavier individuals. We found no differences across racial/ethnic groups except that non-Hispanic Blacks gained more weight than other groups. Women gained more weight than men. Conclusions. We found fewer differences, especially by relative income and education, in weight gain across subpopulations than we had expected. Women and non-Hispanic Blacks gained weight faster than other groups. While large segments of the American population are either overweight (body mass index [BMI] > 25) or obese (BMI ≥ 30), disparities exist in the prevalence of overweight and obesity across population subgroups defined by race/ethnicity, gender, age, or socioeconomic status. 1 – 3 A larger proportion of individuals are overweight or obese among lower-educated groups, Blacks, and Mexican Americans than among other sociodemographic groups, and socioeconomic differences in obesity rates tend to be larger for women than for men. 1 – 3 Although sociodemographic differences in the prevalence of unhealthy weight contribute to health disparities, it is not clear how the current obesity epidemic has contributed to these disparities. The National Health and Nutrition Examination Survey (NHANES), the benchmark for objectively measured national trends, shows no statistically significant differences in increasing obesity rates among racial/ethnic groups for men. 2 This finding, however, may be primarily a consequence of insufficient statistical power for subgroup comparison; although a highly significant increase in severe obesity has occurred for the full population, this increase is not statistically significant for most individual subpopulations. Data from the Behavioral Risk Factor Surveillance System (BRFSS) show significant differences across racial/ethnic groups. However, the direction (widening or narrowing) of the disparities seen depends on the cutpoint used to define unhealthy weight (BMI=25, 27, or 30) and the type of changes (i.e., absolute vs relative) being considered. 1 , 4 Plausible hypotheses have been developed to explain trends of widening or narrowing health disparities related to unhealthy weight. One intriguing theory focuses on the economics of food supply, taking into consideration that individuals with limited financial resources must choose energy-dense foods, which in turn is likely to encourage excessive energy intake. 5 , 6 This process could result in widened disparities across income groups, given that the prices of less energy-dense products, such as fresh produce, have increased more rapidly than the consumer price index over the past 2 decades, whereas the prices of more energy-dense products, such as fats and sweets, have increased slower than the consumer price index. 7 , 8 If the differential costs of diets constitute a primary pathway to disparities in weight gain, differential weight gain would be expected to occur across income groups, but not necessarily by education or race/ethnicity, after adjustment for income. Another possible explanation for increasing disparities is that higher-educated groups tend to make health-improving behavior changes in response to new knowledge more quickly than do lower-educated groups, as has occurred in the case of smoking. 9 Arguments also have been made supporting a narrowing of weight-related disparities over time. Suburban sprawl has been associated with higher rates of obesity, less walking, and chronic conditions related to obesity, after control for individual sociodemographic characteristics, but neighborhoods with characteristics of suburban sprawl (low population density, poorly connected streets, single-mode land use) tend to be characterized by higher income and fewer minorities than are urban neighborhoods (high population density, better connected streets, mixed land use). 10 – 13 It is also possible that factors leading to differential weight gain across population subgroups are less important than secular changes that affect all groups, such as motorization, suburbanization, and increased food availability. If that is so, weight would be expected to increase similarly across groups. We studied trends in weight gain through analysis of BRFSS data for 1986 through 2002. We focused on changes in BMI (mean and 80th percentile) among different sociodemographic groups. We tried to determine whether population differences are primarily related to education, race/ethnicity, relative income, or gender.
