Prevalence and
Trends in
Obesity Among US Adults, 1999-2000
JAMA v.288, n.14, 9oct02
Katherine M. Flegal, PhD; Margaret D. Carroll, MS; Cynthia L. Ogden, PhD; Clifford L. Johnson, MSPH
Context The prevalence of obesity and overweight increased in the United States between 1978 and 1991. More recent reports have suggested continued increases but are based on self-reported data.
Objective To examine trends and prevalences of overweight (body mass index [BMI] 25) and obesity (BMI 30), using measured height and weight data.
Design, Setting, and Participants Survey of 4115 adult men and women conducted in 1999 and 2000 as part of the National Health and Nutrition Examination Survey (NHANES), a nationally representative sample of the US population.
Main Outcome Measure Age-adjusted prevalence of overweight, obesity, and extreme obesity compared with prior surveys, and sex-, age-, and race/ethnicity–specific estimates.
Results The age-adjusted prevalence of obesity was 30.5% in 1999-2000 compared with 22.9% in NHANES III (1988-1994; P<.001). The prevalence of overweight also increased during this period from 55.9% to 64.5% (P<.001). Extreme obesity (BMI 40) also increased significantly in the population, from 2.9% to 4.7% (P = .002). Although not all changes were statistically significant, increases occurred for both men and women in all age groups and for non-Hispanic whites, non-Hispanic blacks, and Mexican Americans. Racial/ethnic groups did not differ significantly in the prevalence of obesity or overweight for men. Among women, obesity and overweight prevalences were highest among non-Hispanic black women. More than half of non-Hispanic black women aged 40 years or older were obese and more than 80% were overweight.
Conclusions The increases in the prevalences of obesity and overweight previously observed continued in 1999-2000. The potential health benefits from reduction in overweight and obesity are of considerable public health importance.
JAMA. 2002;288:1723-1727
Data from the Third National Health and Nutrition Examination Survey (NHANES III; 1988-1994) showed that the prevalence of obesity, defined as a body mass index (BMI) of 30 or higher, had increased by approximately 8 percentage points in the United States after being relatively stable from 1960 to 1980.1, 2 Since those data were published, additional reports from other sources have suggested that these trends are continuing.3-6 However, those reports from the Behavioral Risk Factor Surveillance System (BRFSS) and the Harris Poll have limitations because they are based on self-reported weight and height. Obesity prevalence estimates based on self-reported data tend to be lower than those based on measured data.4 For example, the BRFSS showed a prevalence of obesity of 12% to 14.4% during 1991 to 19944; the corresponding NHANES estimate of 22.5% for 1988 to 19942 was more than 50% higher than the BRFSS estimates. National examination survey data based on measured weight and height data provide the best opportunity to track trends in weight in the United States. In this article we report the results from the latest NHANES data from 1999-2000 regarding population trends in obesity and in the frequency distribution of BMI.
METHODS
Surveys
The NHANES program of the National Center for Health Statistics, Centers for Disease Control and Prevention, includes a series of cross-sectional nationally representative health examination surveys beginning in 1960. Each cross-sectional survey provides a national estimate for the US population at the time of the survey, enabling examination of trends over time in the US population. In each survey a nationally representative sample of the US civilian noninstitutionalized population was selected using a complex, stratified, multistage probability cluster sampling design. Previous national surveys include the first National Health Examination Survey (NHES I, 1960-1962) and the first, second, and third NHANES surveys (NHANES I, 1971-1974; NHANES II, 1976-1980; and NHANES III, 1988-1994).7-10
Beginning in 1999, NHANES became a continuous survey without a break between cycles. The procedures followed to select the sample and conduct the interview and examination were similar to those for previous surveys. This report is based on data for 4115 adult men and women from the first 2 years of the continuous NHANES (1999-2000). Two or more years of data are necessary to have adequate sample sizes for subgroup analyses.
BMI and Obesity
Weight and height were measured in a mobile examination center using standardized techniques and equipment. Body mass index was calculated as weight in kilograms divided by the square of height in meters. For adults, overweight was defined as a BMI of 25.0 or higher, obesity as a BMI of 30.0 or higher, and extreme obesity as a BMI of 40 or higher.2 These definitions are consistent with those of the National Heart, Lung, and Blood Institute and the World Health Organization.11, 12
Data Analysis and Statistical Methods
Statistical analyses were carried out using SAS for Windows software (SAS Institute, Cary, NC) and SUDAAN software (RTI, Research Triangle Park, NC). For all surveys, sampling weights had been calculated that took into account unequal probabilities of selection resulting from the sample design, from nonresponse, and from planned oversampling of certain subgroups. All analyses took into account differential probabilities of selection and the complex sample design. Standard errors were calculated with SUDAAN using Taylor series linearization for NHANES III.13 For NHANES 1999-2000, SEs were calculated using the delete 1 jackknife method,13 partitioning the sample into 52 sampling units and forming 52 replicates by deleting one unit at a time. Statistical hypotheses were tested univariately at the .05 level using a t statistic. To adjust for multiple comparisons when 3 racial/ethnic groups were compared, the Bonferroni method was used. For graphical comparison, the frequency distributions of BMI from both surveys were smoothed using a nonparametric smoothing algorithm, based on sequential calculations of running medians for groups of adjacent points.14
RESULTS
The prevalence of obesity (BMI 30) during 1960 to 2000 in the United States by age and sex categories for those aged 20 to 74 years is shown in Table 1. For surveys up through NHANES II, data were available only for respondents younger than 75 years. The prevalence of obesity was relatively constant from 1960 to 1980, then increased as reported by NHANES III in 1988-1994. The most recent data, from NHANES 1999-2000, show further increases for both men and women and in all age groups. The increases from NHANES II to NHANES III were statistically significant in all sex-age groups. Statistically significant increases also occurred from NHANES III to NHANES 1999-2000, except for the increase for men aged 40 to 59 years, which was not statistically significant but showed the same trend. The increases between NHANES III and NHANES 1999-2000 were almost as large as the increases between NHANES II and NHANES III and were not significantly different.
A more detailed examination of trends by age over a broader age range between NHANES III and NHANES 1999-2000 is possible because both surveys had no upper age limit. The prevalence of obesity for both surveys for all adults and by sex and 10-year age groups is shown in Table 2. Increases in the prevalence of obesity occurred for both men and women and in all age groups. Because the SEs are relatively large, particularly for NHANES 1999-2000, the differences are not always statistically significant, but the trends are similar across all subgroups.
The changes in the prevalence of obesity and extreme obesity between NHANES III and NHANES 1999-2000 by sex and racial/ethnic group for 3 groups non-Hispanic whites, non-Hispanic blacks, and Mexican Americans are shown in Table 3. In each subgroup the prevalence of both obesity and extreme obesity increased between NHANES III and NHANES 1999-2000. The increases were generally similar across all groups, although there was a nonsignificant trend for a larger increase in non-Hispanic black women. For obesity, the increases were not statistically significant for Mexican Americans, although trends were in the same direction as for the other racial/ethnic groups. For extreme obesity, the increases were significant for men and women overall and for non-Hispanic black women. In other racial/ethnic groups, the increases were not statistically significant, although the trends were in the same direction.
More detailed information on the prevalence of overweight and obesity by age, sex, and racial/ethnic group from NHANES 1999-2000 is shown in Table 4. The prevalence of overweight, which was 55.9% in NHANES III, increased to 64.5% (P<.001). The prevalences of overweight and obesity among men varied little by racial/ethnic group and there were no significant differences. Among women, non-Hispanic black women had a higher prevalence of both overweight and obesity than did non-Hispanic white women. For Mexican American women, the prevalence was intermediate between the other 2 groups and was not significantly different from either non-Hispanic white women or non-Hispanic black women. Data on extreme obesity are not shown because the estimates within subgroups were statistically unreliable.
The distribution of BMI in the population was also evaluated. For men aged 60 to 79 years, the distribution of BMI between NHANES III and NHANES 1999-2000 has shifted to the right (Figure 1), but the shift is greater at the upper percentiles of the distribution, indicating that the distribution has become more skewed. This pattern was also seen for men and women aged 20 to 39 years and 40 to 59 years (data not shown). For women aged 60 to 79 years the shift is more uniform (Figure 1).
COMMENT
These data indicate that the trends in BMI and the prevalence of obesity previously observed between the 1976-1980 NHANES II survey and the 1988-1994 NHANES III survey appear to be continuing at a similar level in 1999-2000. Although these increases in obesity observed in NHANES III and NHANES 1999-2000 appear dramatic compared with previous surveys, they may also be viewed as part of a longer-term trend for increases in body size in affluent and well-nourished societies. In the United States, mean BMI appears to have been increasing over a long time, with recent increases perhaps less steep than those earlier.15 Other developed countries are experiencing similar increases, and less developed countries also show increases in obesity as they become more affluent.12 As with NHANES III, the increases seen in NHANES 1999-2000 appear to be occurring in both men and women, in all age groups, and in all racial/ethnic groups studied.
The findings also reflect the difference in prevalence estimates based on measured vs self-reported height and weight. The 2000 BRFSS data3 estimate an obesity prevalence of 19.8% among adults compared with the estimated prevalence of 30.5% in our study. Relatively little is known about the precise causes of these trends.16-18 Although they must reflect energy imbalances in the sense that energy intake must exceed energy expenditure for weight to increase, the nature of the imbalances is not clear. Both dietary intake and physical activity are difficult to measure, and trends in these factors are not easy to evaluate. A more fundamental problem is to identify the social, economic, and cultural forces leading to energy imbalance. Advances in technology, changes in work life, the advent of computers, trends in eating out vs food preparation at home, time pressures, fear of crime, decreases in tobacco use, and many other factors have been suggested, but definitive data are lacking that would clearly associate changes in these factors with the increase in obesity on an individual basis.
The increases in overweight and obesity raise questions about the implications of these trends for health outcomes. Obesity is a risk factor for many chronic conditions including diabetes, hypertension, hypercholesterolemia, stroke, heart disease, certain cancers, and arthritis. Of these conditions, diabetes may be most closely linked to obesity, and its prevalence appears to have increased as the prevalence of obesity increased.19 The increasing incidence of diabetes worldwide is of considerable concern.20 Clinical trials have demonstrated that a structured lifestyle intervention including dietary change, weight loss, and increased physical activity can reduce the risk of progressing to diabetes mellitus from impaired glucose tolerance.21, 22
Other conditions, such as hypercholesterolemia and hypertension, declined between NHANES II and NHANES III at the same time that the prevalence of obesity was increasing.23, 24 Total cardiovascular mortality and mortality from coronary heart disease and stroke have also declined over these years.25 Obesity is a risk factor for these conditions; however, not everyone with these conditions is obese, and not all obese people have these conditions.26, 27 There are several risk factors other than obesity for most of these health conditions, and intervening on these other risk factors may be necessary.11, 26, 27 Changes in other risk factors might also affect trends in these health conditions. It is also possible that some of the conditions associated with obesity may respond to interventions such as change in the fat content of the diet or increases in physical activity that are not necessarily accompanied by large changes in body weight.11
Relatively little is known about the prevention and treatment of overweight and obesity on a population-wide basis.28, 29 On an individual level, structured programs that emphasize lifestyle changes, including education, reduced fat and energy intake, regular physical activity, and regular staff contacts with participants, can produce modest long-term weight loss on the order of 5% to 10% of starting weight.30
It likely will be difficult to reverse the increasing prevalence of overweight and obesity in the United States. Even as long ago as 1960, almost 50% of men and more than 40% of women were overweight, and 11% of men and 16% of women were obese. As was shown previously for the shifts between NHANES II and NHANES III,31 the entire distribution of BMI appears to be affected, with a shift to the right occurring in all age-sex groups. Thus, these appear to be population-wide changes, not limited just to the upper portion of the distribution. Although the health implications of the increases in obesity and the costs and the risks and benefits associated with treatments and interventions have not been completely elucidated, the increase in the prevalence of obesity is clear. The potential health benefits from reduction in overweight and obesity are a matter of considerable public health importance.
Author/Article Information
Author Affiliations: National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Md.
Corresponding Author and Reprints: Katherine M. Flegal, PhD, National Center for Health Statistics, 6525 Belcrest Rd, Room 900, Hyattsville, MD 20782 (e-mail: kmf2@cdc.gov). Author Contributions: Study concept and design: Flegal.
Acquisition of data: Johnson.
Analysis and interpretation of data: Flegal, Carroll, Ogden, Johnson.
Drafting of the manuscript: Flegal.
Critical revision of the manuscript for important intellectual content: Flegal, Carroll, Ogden, Johnson.
Statistical expertise: Flegal, Carroll,
Administrative, technical, or material support: Johnson.
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source: http://jama.ama-assn.org/issues/v288n14/rfull/joc21463.html 13oct02
THE HARRIS POLL® #11, March 6, 2002
The Obesity Epidemic Is Getting Even Worse
Americans continue to get fatter, with 80% over recommended weight and 33% who
are now twenty percent or more overweight.
by Humphrey Taylor
In the early 1990s I enjoyed my 15 seconds (if not 15 minutes) of fame when I was widely quoted as writing that "Americans are the fattest people on earth and getting fatter every year." Alas, the trend continues.
Every year since 1983, Harris Interactive has asked a nationwide cross section of adults several questions to determine how many are overweight and underweight, using the Metropolitan Life tables based on weight, height and body frame.
The Harris Poll®, which also measures smoking behavior and seatbelt use, was conducted with a nationwide cross section of 1,011 adults interviewed by telephone between January 16 - 21, 2002, finds that:
Among people over 25 (the population for which the Metropolitan Life tables were developed) 80% of the public are overweight, up from 58% in 1983, 64% in 1990 and 71% in 1995.
Fully 33% are now twenty percent overweight, a reasonable measure of obesity, compared to 15% in 1983, 16% in 1990, and 22% in 1995. In other words, obesity has more than doubled from less than one-sixth of the population eighteen years ago to one-third today.
While the proportion of adults who smoke cigarettes is down to 23% in this survey, this is a decline of only seven points (from 30%) since 1983, and of three points (from 26%) since 1990. Indeed, all the modest changes in the smoking rate, as we have measured it over the last few years, are within the possible sampling error for this survey. So if there has been any reduction in the smoking rate over the last decade, it has been extremely modest.
81% of all adults say that they now wear seatbelts when in the front seat of a car. This is a huge increase over the 19% who said this in 1983, the 65% in 1990 and the 73% in 1995. This is perhaps the biggest single success story on public health over the last twenty years. One reason for this huge change was the laws passed in the 1980s by states to mandate seat belt use. It’s a powerful example that legislation, even when weakly enforced as it is in most states, can change both attitudes and behavior very dramatically. Another reason is that – unlike smoking cessation or weight control – seat belt use requires no self-discipline, no sacrifice of gratification and no need to overcome addiction. There is gain without pain. Success and failure in attempts to lose weight
Obesity continues to increase even though many people are trying to lose weight and a surprisingly large number claim to have been successful.
This survey found that:
Most people (60%) say they would like to lose weight, including 72% of those who are overweight (as well as some of those who are not).
A similar proportion of all adults (58%) say they have made a serious effort to lose weight, including 65% of those who are overweight now (and substantial numbers who are not overweight).
More than half (57%) of those who say they successfully lost weight say they have managed to stay at more or less the same weight. This represents 28% of all adults. So what? The health impact of obesity
A recent issue of Issue Focus published by Grantmakers in Health reports that:
"According to U.S. Surgeon General David Satcher, overweight and obesity may soon cause as much preventable disease and death as cigarette smoking. The conditions are already responsible for as many as 300,000 premature deaths each year and cost the nation $117 billion in 2000 alone.
Excess Pounds, Extra Problems
Obesity is associated with an increased risk for:
Type 2 diabetes Hypertension High blood cholesterol Heart disease Stroke Cancer Gallbladder diseases Asthma Osteoarthritis Depression Complications in pregnancy Sleep apnea While individual body weight has a complex set of causes, most researchers attribute the recent increase in obesity among both adults and children to two simple facts: We are eating more and exercising less. In the 1990s, Americans consumed more food and several hundred more calories per day than they did in the 1970s. Why? Fewer meals were eaten at home, average portion sizes grew, and the availability of convenience foods – foods that are high in fat and sugar – exploded."
Dr. Louis Aronne, clinical associate professor of Medicine at Weill Medical College at Cornell University in New York City and one of the nation’s leading obesity experts, believes that if Americans were to focus on lowering their Body Mass Index just a few points the associated health benefits would be enormous. Body mass index, or BMI, is determined by a measurement based on height and weight. It is the most frequent tool doctors use to determine a person’s degree of obesity and how it correlates with other health risks.
"We’re not talking about unrealistic goals," says Dr. Aronne. "If Americans were to make the effort to manage their weight using a variety of options, including better nutrition, more exercise, approved medications or even surgical approaches, we would be rewarded with significantly better health."
For an easy way to determine BMI, visit www.yourbmi.com.
Humphrey Taylor is the chairman of The Harris Poll®, Harris Interactive.
TABLE 1 SMOKING, OVERWEIGHT AND SEAT BELT USE
TRENDS 1983 – 2002
Base: All adults over 25
Smoke Are 20% or More Always Wear Cigarettes1 Overweight Overweight* Seatbelts** 1983 % 30 58 15 19 1984 % 28 56 N/A 27 1985 % 30 62 15 41 1986 % 27 59 N/A 55 1987 % 28 59 15 57 1988 % 26 64 18 60 1989 % 28 61 17 63 1990 % 26 64 16 65 1991 % 25 63 15 69 1992 % 24 66 N/A 70 1994 % 26 69 N/A 71 1995 % 25 71 22 73 1996 % 24 74 24 75 1997 % 26 72 27 74 1998 % 26 76 28 77 1999 % 24 74 27 77 2000 % 21 79 32 79 2001 % 25 76 32 81 2002 % 23 80 33 81
*Adults over 25 (for weight only).
**When in front seat of car.
N/A=Not available.
NOTES:
Almost all these surveys were conducted in January or February in the years
listed.
1 The 23% of the public who smoke cigarettes does not include others who do not
smoke cigarettes but smoke cigars (2%), a pipe (less than 0.5%) or who chew
tobacco (1%). In all, according to our latest survey, 26% are exposed to tobacco
through smoking or chewing (see Table 2).
TABLE 2 USE OF OTHER TYPES OF TOBACCO
"Do you smoke a pipe or cigars or use chewing tobacco?"
Base: All adults
All Smoke Cigarettes Don’t Smoke Adults Now Cigarettes Now % % % Pipe 1 2 * Cigars 4 11 2 Chewing tobacco 1 1 1
NOTE: Those who use any type of tobacco including cigarettes: 26%.
* Less than 0.5%.
TABLE 3 WOULD LIKE TO LOSE WEIGHT
"Would you like to lose weight, or not?"
Base: All adults
Within Total Underweight Range Overweight % % % % Would like 60 12 24 72 Would not 40 88 76 28
TABLE 4 HOW MANY TIMES HAVE TRIED TO LOSE WEIGHT
"How many times, if ever, in your life have you made a serious effort to lose weight?"
Base: All adults
Within Total Underweight Range Overweight % % % % Have ever tried to 58 27 40 65 lose weight (net) Once or twice 28 15 24 29 3 – 5 times 15 11 7 17 More than 5 times 15 2 10 18 MEAN (if tried) 8 3 8 9 MEDIAN (if tried) 3 2 2 3
TABLE 5 THE LAST TIME YOU TRIED TO LOSE WEIGHT WERE YOU SUCCESSFUL?
"The last time you tried to lose weight were you successful in losing weight, or not?"
Base: Tried to lose weight
Within Total Underweight Range Overweight % % % % Successful 85 87 88 86 Not successful 13 13 11 12 Not sure/Refused 2 - 2 3
NOTE: The 85% of those who tried to lose weight who say they successfully did so represents 50% of all adults.
TABLE 6 IF SUCCEEDED IN LOSING WEIGHT HAVE YOU MANAGED TO KEEP IT OFF?
"Have you managed to stay at more or less the same weight you were then, or have you put most of the weight you lost back on again?"
Base: Was successful in losing weight
Within Total Underweight Range Overweight % % % % Managed to stay 57 93 78 53 at (reduced) weight Put most of 41 7 22 46 weight on again Not sure 1 - - 2
NOTE: The 57% of those who successfully lost weight who have managed to stay at their reduced weight represents 28% of all adults.
Methodology
The Harris Poll® was conducted by telephone within the United States between January 16–21, 2002 among a nationwide cross section of 1,011 adults. Figures for age, sex, race, education, number of adults and number of voice/telephone lines in the household were weighted where necessary to align them with their actual proportions in the population.
In theory, with a probability sample of this size, one can say with 95 percent certainty that the results have a statistical precision of plus or minus 3 percentage points of what they would be if the entire adult population had been polled with complete accuracy. Unfortunately, there are several other possible sources of error in all polls or surveys that are probably more serious than theoretical calculations of sampling error. They include refusals to be interviewed (non-response), question wording and question order, interviewer bias, weighting by demographic control data and screening (e.g., for likely voters). It is impossible to quantify the errors that may result from these factors.
These statements conform to the principles of disclosure of the National Council on Public Polls.
J15652 Q520 – Q545
source: http://www.harrisinteractive.com/harris_poll/index.asp?PID=%20288 13oct02
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