Studies have suggested that obesity prevalence varies by income and educational level, although patterns might differ between high-income and low-income countries ( 1 – 3 ). Previous analyses of U.S. data have shown that the prevalence of obesity varied by income and education, but results were not consistent by sex and race/Hispanic origin ( 4 ). Using data from the National Health and Nutrition Examination Survey (NHANES), CDC analyzed obesity prevalence among adults (aged ≥20 years) by three levels of household income, based on percentage (≤130%, >130% to ≤350%, and >350%) of the federal poverty level (FPL) and individual education level (high school graduate or less, some college, and college graduate). During 2011–2014, the age-adjusted prevalence of obesity among adults was lower in the highest income group (31.2%) than the other groups (40.8% [>130% to ≤350%] and 39.0% [≤130%]). The age-adjusted prevalence of obesity among college graduates was lower (27.8%) than among those with some college (40.6%) and those who were high school graduates or less (40.0%). The patterns were not consistent across all sex and racial/Hispanic origin subgroups. Continued progress is needed to achieve the Healthy People 2020 targets of reducing age-adjusted obesity prevalence to 130% to ≤350%, and >350% of FPL. The cut point for participation in the Supplemental Nutrition Assistance Program is 130% of the poverty level, and 350% provides relatively equal sample sizes for each of the three income groups. Education was categorized as high school graduate or less, some college, and college graduate. All estimates were adjusted to account for the complex survey design, including examination sample weights. Estimates were age-adjusted to the 2000 projected U.S. Census population using the age groups 20–39, 40–59, and ≥60 years. Confidence intervals for estimates were calculated using the Wald method. Differences between income and education groups were tested using a two-sided, univariate t-statistic, with statistical significance defined as a p-value of 130 to ≤350% FPL 3,331 40.8 (38.2–43.4) 40.2 (36.5–43.9) 48.8 (44.6–52.9) 11.2 (6.6–15.8) 45.0 (40.7–49.2) >350% FPL 2,992 31.2 (28.3–34.2)†,§ 30.6 (27.3–34.0)†,§ 49.3 (43.4–55.1) 10.7 (8.3–13.1) 39.1 (33.9–44.3) Household income, women ≤130% FPL 1,835 45.2 (42.5–48.0) 42.0 (37.4–46.5) 55.8 (52.2–59.4) 17.2 (10.3–24.1) 48.7 (43.1–54.4) >130 to ≤350% FPL 1,702 42.9 (40.1–45.8) 42.5 (38.8–46.1) 59.4 (53.7–65.2) 11.7 (5.6–17.7) 44.6 (37.4–51.8) >350% FPL 1,453 29.7 (26.1–33.3)†,§ 27.9 (24.0–31.9)†,§ 56.7 (50.0–63.5) 9.7 (5.8–13.7) 42.9 (35.2–50.5) Household income, men ≤130% FPL 1,627 31.5 (28.5–34.4) 28.5 (24.4–32.6) 33.8 (28.9–38.6) 11.8 (4.7–18.9) 35.9 (30.9–40.8) >130 to ≤350% FPL 1,629 38.5 (35.1–41.9)† 37.8 (32.7–43.0)† 35.6 (30.7–40.5) 10.3 (5.6–15.0) 44.6 (40.1–49.2)† >350% FPL 1,539 32.6 (29.4–35.8)§ 32.9 (29.2–36.6) 42.7 (35.8–49.6)† 11.8 (7.9–15.7) 35.6 (27.8–43.4)§ Education, both sexes High school graduate or less 4,714 40.0 (37.9–42.2) 38.1 (34.5–41.6) 46.6 (42.8–50.4) 11.5 (7.6–15.5) 43.8 (40.6–47.0) Some college 3,231 40.6 (38.1–43.1) 39.2 (35.9–42.5) 50.5 (46.3–54.7) 12.4 (8.9–15.8) 42.9 (38.2–47.5) College graduate 2,683 27.8 (25.0–30.7)¶,** 27.5 (24.1–30.9)¶,** 47.3 (43.3–52.1) 11.1 (8.7–13.6) 36.9 (30.6–43.2)¶ Education, women High school graduate or less 2,277 45.3 (42.3–48.3) 43.3 (38.7–47.8) 57.9 (53.2–62.6) 11.4 (6.1–16.7) 49.6 (45.6–53.7) Some college 1,777 41.2 (38.5–43.9) 38.9 (35.1–42.7) 58.8 (53.8–63.9) 13.3 (7.6–19.0) 43.0 (36.3–49.8) College graduate 1,355 27.8 (24.1–31.5)¶,** 27.0 (22.3–31.6)¶,** 52.1 (47.4–56.8)** 11.3 (7.6–15.0) 36.1 (26.5–45.6)¶ Education, men High school graduate or less 2,437 35.5 (33.0–37.9) 34.1 (29.7–38.5) 36.0 (30.7–41.2) 11.0 (5.7–16.2) 37.7 (34.0–41.4) Some college 1,454 40.0 (35.9–44.1) 39.9 (34.7–45.1) 38.2 (32.7–43.7) 10.3 (5.6–15.1) 42.9 (36.0–49.9) College graduate 1,328 27.9 (24.3–31.5)¶,** 28.1 (24.1–32.1)** 40.4 (32.4–48.3) 11.0 (7.9–14.1) 38.5 (28.1–48.8) Abbreviations: CI = confidence interval; FPL = federal poverty level. *Age-adjusted by the direct method to the 2000 projected U.S. Census population using the age groups 20–39, 40–59, and ≥60 years. † Significantly different from ≤130% FPL, p 130 to ≤350% FPL, p 350% of FPL for women. For >350% of FPL for men also significant quadratic trend. All p<0.05. The figure above is a line graph showing the prevalence of obesity among adults, by household income and sex, from 1999–2002 to 2011–2014. FIGURE 2 Obesity prevalence among adults, by education level and sex — National Health and Nutrition Examination Survey, 1999–2002 to 2011–2014*† * Estimates age-adjusted by the direct method to the 2000 projected U.S. Census population using the age groups 20–39, 40–59, and ≥60 years. † Significant linear trends for all groups (p<0.01) except men who were college graduates. For women college graduates p = 0.056. The figure above is a line graph showing the prevalence of obesity among adults, by education level and sex, from 1999–2002 to 2011–2014. Discussion During 2011–2014, the relationships between obesity and income, and obesity and education were complex, differing among population subgroups. Whereas overall obesity prevalence decreased with increased levels of income and educational attainment among women, the association was more complex among men. Similar to results based on data from 2005–2008 ( 4 ), during 2011–2014, obesity prevalence was lower in the highest income group among women, but this was not the case among men. In fact, among non-Hispanic black men the prevalence of obesity was higher in the highest income group than in the lowest income group. Both women and men who were college graduates, on the other hand, had lower prevalences of obesity than did persons with less education. In general, prevalence of obesity among women was lowest among college graduates, although among non-Hispanic Asians there was no difference in prevalence by level of education. This relationship was not seen when obesity was examined by income level. For example, obesity prevalence was lower in the highest income group among non-Hispanic white women, but among non-Hispanic black women, prevalence did not differ between the highest and lowest household income groups. In contrast, among both non-Hispanic black women and non-Hispanic white women, the prevalence of obesity was lower among college graduates than among women with some college. This difference in the relationship between obesity and income and obesity and education has been reported in at least one other study ( 7 ) in children. These findings demonstrate that lower levels of income and education are not universally associated with obesity; the association is complex and differs by sex and race/Hispanic origin. This is the first report to describe differences in obesity prevalence by income and education among non-Hispanic Asian adults. There were no significant differences in prevalence by income or education among either non-Hispanic Asian women or men; however, there was a pattern of decreasing prevalence with increasing income among non-Hispanic Asian women. The findings in this report are subject to at least two limitations. First, BMI is a proxy for body fat and BMI ≥30 was applied to persons in all racial/Hispanic origin groups, which might result in underestimating health risks for certain populations. For example, it has been suggested that the BMI cut point (≥30 kg/m2) that typically defines obesity might be too high for Asians and underestimate associated health risks ( 8 , 9 ). Second, the small sample size among some subgroups reduced the ability to detect differences when differences exist. Additional years of data might provide more information about obesity prevalence by income, especially among non-Hispanic Asian women. Trends in obesity prevalence over time show that differences by income and education have existed at least since 1999–2002 among women. Among men, college graduates have consistently had a lower prevalence of obesity, whereas differences by household income have been less consistent. Further study is needed to understand the reasons for the different patterns by sex and race/Hispanic origin in the relationship between obesity and income or education. Summary What is already known about this topic? Studies have suggested that obesity prevalence varies by income or education, although patterns might differ in high and low income countries. What is added by this report? Analysis of data from the 2011–2014 National Health and Nutrition Examination Survey (NHANES) examining the association between obesity and education and obesity and income among U.S. adults demonstrate that obesity prevalence patterns by income vary between women and men and by race/Hispanic origin. The prevalence of obesity decreased with increasing income in women (from 45.2% to 29.7%), but there was no difference in obesity prevalence between the lowest (31.5%) and highest (32.6%) income groups among men. Moreover, obesity prevalence was lower among college graduates than among persons with less education for non-Hispanic white women and men, non-Hispanic black women, and Hispanic women, but not for non-Hispanic Asian women and men or non-Hispanic black or Hispanic men. The association between obesity and income or educational level is complex and differs by sex, and race/non-Hispanic origin. What are the implications for public health practice? NHANES will continue to be an important source of data on disparities in obesity prevalence. These data will help track the Healthy People 2020 objective of reducing obesity disparities and might inform CDC, state, or local obesity prevention programs.
