Obesity in Ethnic and Social Class Groups: US, 1976-2008
Abstract and Introduction
This study examined trends in US obesity and overweight prevalence and body mass index (BMI) among 30 immigrant groups, stratified by race/ethnicity and length of immigration, and among detailed education, occupation, and income/poverty groups from 1976 to 2008. Using 1976–2008 National Health Interview Surveys, differentials in obesity, overweight, and BMI, based on self-reported height and weight, were analyzed by using disparity indices, logistic, and linear regression. The obesity prevalence for the US population aged ≥18 tripled from 8.7% in 1976 to 27.4% in 2008. Overweight prevalence increased from 36.9% in 1976 to 62.0% in 2008. During 1991–2008, obesity prevalence for US-born adults increased from 13.9 to 28.7%, while prevalence for immigrants increased from 9.5 to 20.7%. While immigrants in each ethnic group and time period had lower obesity and overweight prevalence and BMI than the US-born, immigrants' risk of obesity and overweight increased with increasing duration of residence. In 2003–2008, obesity prevalence ranged from 2.3% for recent Chinese immigrants to 31–39% for American Indians, US-born blacks, Mexicans, and Puerto Ricans, and long-term Mexican and Puerto Rican immigrants. Between 1976 and 2008, the obesity prevalence more than quadrupled for those with a college education or sales occupation. Although higher prevalence was observed for lower education, income, and occupation levels in each period, socioeconomic gradients in obesity and overweight decreased over time because of more rapid increases in prevalence among higher socioeconomic groups. Continued immigrant and socioeconomic disparities in prevalence will likely have substantial impacts on future obesity trends in the US.
The prevalence of obesity has risen dramatically in the United States. The rates for adults have more than doubled during the past 3 decades. Increases in obesity prevalence have been marked across all gender, race, and socioeconomic groups. Because of a relatively high prevalence, a rapidly increasing trend, and large social-group disparities, adult obesity is recognized as a major public health problem in the US.
While obesity data for US adults are routinely available by age, gender, and race/ethnicity, prevalence estimates for various immigrant and socioeconomic groups are less well known, particularly temporal obesity patterns among them. The immigrant population in the US has increased four-fold in the last four decades. In 2008, there were 38 million immigrants, an increase of 28.4 million since 1970. Immigrants currently account for 12.5% of the total US population.
Given such a rapid population increase, analysis of obesity patterns among immigrants of various ethnicities assumes a special importance. In addition to ethnic and immigrant disparities, monitoring socioeconomic inequalities in health has long represented an important research and policy focus. Socioeconomic inequalities as well as immigrant differentials in health, life expectancy, and mortality from major causes of death have not only remained substantial in the US but have also increased over time. Inequalities in chronic disease risk factors such as obesity, smoking, physical inactivity, and poor diet have contributed greatly to the persistence and/or widening of the health gradients. The purpose of this study was to describe national trends in immigrant and social class inequalities in the prevalence of obesity and overweight and to identify immigrant and social class groups who are at high risk of obesity and who have experienced substantial increases in their obesity rates. Specifically, we (1) estimate over time changes in obesity and overweight prevalence among 30 major immigrant groups stratified by race/ethnicity and length of immigration and among detailed education, occupation, and income groups, using large, nationally representative samples of US adults and (2) compare the magnitude of ethnic-immigrant and socioeconomic disparities in obesity and overweight prevalence among adults aged ≥18 over time.