WASHINGTON, D.C. -- Blacks are among the most likely in the United States to be very obese, with about 9% falling into obese class II and 6% obese class III -- the highest Body Mass Index (BMI) categories. Asians are by far the least likely to fall into these two classes of obesity. Hispanics are on par with whites for each obesity class.
Relationships by race and the others presented in this article hold true even when controlling for age, ethnicity, race, marital status, gender, employment, income, education, and region.
The findings are based on data collected as part of the Gallup-Healthways Well-Being Index from Jan. 1, 2010 through May 31, 2012, and include interviews with more than 800,000 American adults aged 18 and older. Gallup calculates respondents' BMIs using the standard formula based on their self-reported height and weight.
An average of 26.3% of all respondents surveyed reported a height and weight that led to a BMI calculation high enough to be categorized as obese. Gallup and Healthways have been tracking Americans' BMI levels daily since January 2008 and find obesity is slightly higher now than it was in 2008.
The World Health Organization defines a normal BMI range as being 18.50 to 24.99. It labels BMIs of 25.00 to less than 30.00 as overweight/pre-obese. BMIs of 30.00 or higher fall into one of three classes of obesity:
Obese class I = 30.00 to 34.99
Obese class II = 35.00 to 39.99
Obese class III = 40.00 or higher
Those with BMIs of 40 or higher -- obese class III -- are also frequently considered "morbidly obese." Based on their self-reports of height and weight, nearly 4% of American adults overall are this obese, with a total of about one in 10 with BMIs high enough to place them in the two highest obesity classes. However, all groups are more likely to fall on the lower end of the obesity scale than the higher end.
While men are more likely than women in general to be obese, including obese class I, women and men are equally likely to fall into obese class II -- and women are, in fact, more likely than men to have a BMI high enough to put them in obese class III. The U.S. Centers for Disease Control and Prevention also previously found that women are more likely than men to fall into obese class III, based on data from the 2007-2008 National Health and Nutrition Examination Survey, which measured respondents' actual height and weight.
As with obesity in general, each of the three classes of obesity rise precipitously as Americans age -- peaking in late middle-age -- but then drop off as Americans enter their 70s. Part of the drop-off as age increases may be related to the shorter life expectancy among those who are obese.
Income and education level are also related to Americans' obesity levels. Those Americans with the lowest income levels and who are the least educated are the most likely to be very obese.
About 5% of low-income Americans have BMIs high enough to put them in obese class III, but that falls to 2.9% among those with annual incomes of $36,000 to less than $90,000, and 1.8% among high-income Americans ($90,000 or more per year).
Similarly, 4.4% of Americans with a high school education or less are categorized as class III obese. That falls as education rises -- to 3.6% among Americans with some college or vocational education, then to 2.3% among college graduates, and further to 1.8% among postgraduates.
Unemployed Americans are more likely than those who are employed to have high enough BMIs to be in obese classes II and III. But, the unemployed are only slightly more likely than the employed to be in obese class I.
This finding expands on a recent Gallup analysis showing that the unemployed are more likely than the employed to be obese in general. It may reveal that a lower level of obesity isn't as prohibitive to working as the more severe classes of obesity can be.
Obesity of all types is related to higher levels of chronic conditions such as high blood pressure and diabetes as well as a lower quality of life -- including worse emotional health, more daily pain, and more missed work. It is also tied to shorter life expectancy. The more obese an individual is, the more likely he or she is to experience these types of problems. And, those who are morbidly obese -- with BMIs of 40 or higher -- are the most at risk.
Gallup-Healthways Well-Being Index data reveal that black, low-income, middle-aged, less-educated, and unemployed Americans are the most likely to be very obese, including morbidly obese. As government, business, and healthcare leaders continue to try to develop policies and programs to reduce obesity in the United States, they may need to target specific efforts toward these high-risk groups. On the other hand, the study of those groups that are less likely to be obese -- including Asians, very young and very old Americans, and those with higher socioeconomic status -- may provide insights into behaviors and practices associated with a more normal weight.
The U.S. government is already taking steps to further address the nation's obesity problem, with the U.S. Preventative Services Task Force putting out in June new guidelines for obesity screenings. The task force is recommending that all adults get screened for obesity and that doctors should refer patients with a BMI of 30 or higher to "intensive, multicomponent behavioral interventions."
As more Americans gain access to doctors through the 2010 Affordable Care Act, it is possible that guidelines such as these will have an even greater impact on reducing obesity in the United States.
Gallup will be publishing an in-depth series further exploring why certain groups -- such as blacks and middle-aged Americans -- are more likely to be obese than others -- such as Asians. The forthcoming analysis will reveal the key predictors of obesity and will shed light on what else can be done to reduce it.
Results are based on telephone interviews conducted as part of the Gallup-Healthways Well-Being Index survey Jan. 1 2010-May 31, 2012, with a random sample of 808,660 adults, aged 18 or older, living in all 50 U.S. states and the District of Columbia.
For results based on the total sample of national adults, one can say with 95% confidence that the maximum margin of sampling error is ±1 percentage point.
Interviews are conducted with respondents on landline telephones and cellular phones, with interviews conducted in Spanish for respondents who are primarily Spanish-speaking. Each sample includes a minimum quota of 400 cell phone respondents and 600 landline respondents per 1,000 national adults, with additional minimum quotas among landline respondents by region. Landline telephone numbers are chosen at random among listed telephone numbers. Cell phones numbers are selected using random digit dial methods. Landline respondents are chosen at random within each household on the basis of which member had the most recent birthday.
Samples are weighted by gender, age, race, Hispanic ethnicity, education, region, adults in the household, and phone status (cell phone-only/landline only/both, cell phone mostly, and having an unlisted landline number). Demographic weighting targets are based on the March 2011 Current Population Survey figures for the aged 18 and older non-institutionalized population living in U.S. telephone households. All reported margins of sampling error include the computed design effects for weighting and sample design.
In addition to sampling error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.
For more details on Gallup's polling methodology, visit http://www.gallup.com/.