Prevalence of Obesity, Diabetes, and Obesity-Related Health Risk Factors, 2001 FREE

Obesity and diabetes are major causes of morbidity and mortality in the United States.^1- 3 Evidence from several studies indicates that obesity and weight gain are associated with an increased risk of diabetes^4- 5 and that intentional weight loss reduces the risk that overweight people will develop diabetes.⁶ Each year, an estimated 300 000 US adults die of causes related to obesity,⁷ and diabetes is the sixth leading cause of death.³ Correspondingly, both obesity and diabetes generate immense health care costs.^8- 9

We recently reported that the prevalence of obesity and diabetes among US adults increased substantially from 1990 to 2000.¹⁰ We used data from the 2001 Behavioral Risk Factor Surveillance System (BRFSS) to examine whether these increases are continuing. In addition, we examined the association between obesity and several other important health risk factors, as well as self-rated general health.

The BRFSS is a cross-sectional telephone survey conducted by the Centers for Disease Control and Prevention and state health departments. The BRFSS questionnaire consists primarily of questions about personal behaviors that increase risk for 1 or more of the 10 leading causes of death in the United States. The BRFSS uses a multistage cluster design based on random-digit dialing to select a representative sample from each state's noninstitutionalized civilian residents aged 18 years or older. Data from each state are pooled to produce nationally representative estimates. A detailed description of the survey methods is available elsewhere.^11- 12

The 2001 BRFSS included questions on health status, health care access, exercise, hypertension awareness, cholesterol awareness, asthma, diabetes, arthritis, immunization, tobacco use, alcohol consumption, firearms, disability, physical activity, prostate cancer screening, colorectal cancer screening, and human immunodeficiency virus or acquired immunodeficiency syndrome (all BRFSS questionnaires from 1991 to 2002 are available at http://www.cdc.gov/brfss).

We used data on self-reported weight and height to calculate body mass index (BMI), calculated as weight in kilograms divided by the square of height in meters. Participants were classified as overweight (class 1) if their BMI ranged from 25 through 29.9. We further divided obesity (BMI ≥30) into 2 levels to analyze the association between BMI groups and medical conditions: BMI of 30 through 39.9, class 2; BMI of 40 or higher, class 3.¹³ Self-reported weight and height were assessed by asking, "About how much do you weigh without shoes?" and "About how tall are you without shoes?" Diagnosed diabetes was assessed by asking, "Have you ever been told by a doctor that you have diabetes?" The answer was coded yes or no to be similar to our previous reports. Those with gestational diabetes were considered to have diabetes. The type of diabetes was not assessed.

High blood pressure was assessed by asking, "Have you ever been told by a doctor, nurse, or other health professional that you have high blood pressure?" High cholesterol was assessed by asking, "Have you ever been told by a doctor, nurse, or other health professional that your blood cholesterol is high?" Asthma was assessed by asking, "Have you ever been told by a doctor, nurse, or other health professional that you had asthma?" Arthritis was assessed by asking, "Have you ever been told by a doctor that you have arthritis?" Health status was assessed by asking, "Would you say that in general your health is: excellent, very good, good, fair, or poor?"

SAS and SUDAAN statistical software programs were used in the analyses and to account for the complex sampling design.^14- 15 We used Proc Logistic in SUDAAN to generate the odds ratios (ORs) and their 95% confidence intervals (CIs) for the association of BMI and medical conditions. Because of the large sample size (195 005 participants), we have not emphasized statistical testing.

The prevalence of obesity among US adults (Table 1) increased to 20.9% in 2001 from 19.8% in 2000, an increase of 5.6%. Since 1991 the percentage of those who were obese increased by 74% (1991 prevalence, 12%). That prevalence rate represents an estimated 21.4 million obese men and 22.9 million obese women, for a total of 44.3 million obese US adults. The percentage of adults with a BMI of 40 or higher was 2.3% (1.7% men, 2.8% women) vs 2.1% in 2000 and 0.9% in 1991. Among racial groups, blacks had the highest rate of obesity (31.1%). Among states, Mississippi had the highest rate of obesity (25.9%) and Colorado the lowest (14.4%; Table 2, Figure 1, A). Since 1991, the percentage of overweight adult participants increased from 45% to 58%. Of those overweight in 2001, 65.9% were men and 49.9% were women.

The prevalence of those diagnosed with diabetes increased to 7.9% in 2001 from 7.3% in 2000, an increase of 8.2% and an increase of 61% since 1990 (1990 prevalence, 4.9%). Thus, in 2001, an estimated 16.7 million US adults could have been diagnosed as having diabetes (6.9 million men; 9.8 million women). In 2001, 3.4% of US adults (2.9% men, 3.8% women) were both obese and had diabetes, an increase of 1.4% in 1991. Blacks had the highest rate of diagnosed diabetes (11.2%) among all race groups, and adults with less than a high school education had the highest rate (13.0%) among the educational levels. Of US adults aged 60 years or older, 15.1% had diagnosed diabetes. Alabama had the highest rate of diagnosed diabetes (10.5%) and Minnesota the lowest (5.0%; Table 2, Figure 1, B).

Both overweight and obesity were significantly associated with diabetes, high blood pressure, high cholesterol levels, asthma, arthritis, and fair or poor health status (Table 3). Compared with adults with normal weight, those with a BMI of 40 or higher had an OR of 7.37 (95% CI, 6.39-8.50) for diagnosed diabetes, 6.38 (95% CI, 5.67-7.17) for high blood pressure, 1.88 (95% CI, 1.67-2.13) for high cholesterol levels, 2.72 (95% CI, 2.38-3.12) for asthma, 4.41 (95% CI, 3.91-4.97) for arthritis, and 4.19 (95% CI, 3.68-4.76) for fair or poor health.

Our study, the largest telephone survey of adults in the United States, shows a continuing increase of obesity and diabetes in both sexes, all ages, all races, all educational levels, and all smoking levels. Because of the strong association between overweight and obesity and several well-established risk factors for morbidity and mortality, reversing the obesity epidemic is an urgent priority.

However, these rates are no doubt substantial underestimates. First, individuals without telephones are not included in BRFSS, and such persons are likely to be of low socioeconomic status, a factor associated with both obesity and diabetes.^16- 17 Second, in validation studies of self-reported weight and height, overweight participants tend to underestimate their weight, and all participants tend to overestimate their height.^18- 20 Recent estimates of obesity among US adults is about 30% based on measured weight and height.²¹ Third, undiagnosed diabetes was not counted; recent estimates indicate that about 35% of all persons with diabetes have not been diagnosed.³

Both obesity and type 2 diabetes are preventable. Previous studies have demonstrated that changes in lifestyle are effective in preventing both diabetes and obesity in high-risk adults with impaired glucose tolerance.^22- 23 Increasing physical activity, improving diet, then sustaining these lifestyle changes can reduce both body weight and risk of diabetes. We found that in 2001, 25.5% of US adults did not engage in any leisure-time physical activity. This is a modest decrease from a 27.0% rate in 2000, but it shows that current physical activity levels are still far below what they need to be.

We previously reported that less than 20% of US adults who were trying to lose or maintain weight were following recommendations to eat fewer calories and increase physical activity to at least 150 minutes per week.¹⁰ Health professionals must continue to stress the importance of a balanced diet and physical activity for healthy weight loss. In US society, men and women must overcome many obstacles to make the best choices for optimal health.

Although clinical preventive services to identify and control hypertension, elevated cholesterol levels, asthma, arthritis, and diabetes remain important medical priorities nationally, development and implementation of national programs to promote a balanced diet, increase physical activity, and maintain weight control must be national priorities as well.