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Obesity Update

Joyner, Michael J.

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Exercise and Sport Sciences Reviews: January 2003 - Volume 31 - Issue 1 - p 1-2
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Two recent publications highlight a variety of issues related to the ongoing and increasing epidemic of obesity in the United States in specific and the developed world in general. The October 9, 2002, issue of JAMA: The Journal of the American Medical Association has two reports on the prevalence and trends in obesity among U.S. adults and U.S. children and adolescents in 1999–2000 (1,4). There is an additional report on trends in “class 3” (severe) obesity in the United States during the same time period (2). Additionally, in September 2002 the Food and Nutrition Board of the National Academies of Sciences ( released a massive report titled “Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids” (3). This report also focused on the role of physical activity and exercise in preventing obesity and obesity-related health complications. The Food and Nutrition Board has released similar reports at regular intervals in the past, but this is the first report to specifically highlight the role of exercise in conjunction with diet as a key factor in the fight against obesity. Both the JAMA articles and the Food and Nutrition Board report provide a wealth of information related to obesity and physical activity in the United States

“Prevalence and trends in obesity among U.S. adults, 1999–2000” (1). This study reports results from the NHANES study and compares current values obtained beginning in 1999 with values of similar surveys conducted beginning in the 1960s. Changes in the National Health and Nutrition Examination Survey (NHANES) methodology (it is now a continuous survey without a break between cycles) are highlighted and the similarities and differences between the previous discrete samples are discussed. Data in this manuscript come from a survey, conducted in 1999 and 2000, of 4115 adults. Overweight is defined as a body mass index (BMI) of greater than or equal to 25 and obesity as a BMI greater than or equal to 30. The main finding is that the age-adjusted prevalence of obesity increased from 22.9% in NHANES 3 (1988–1994) to 30.5% in 1999–2000. The prevalence of overweight individuals also increased from 55.9% in the 1988–1994 study to 64.5% in the current study. Additionally, “extreme obesity” (BMI > 40) went from 2.9% (1988–1994) to 4.7% in the most recent survey. The prevalence of individuals who are overweight and obese increased in both genders and all ethnic groups. Especially troublesome was the observation that among non-Hispanic African-American women aged 40 yrs or older, more than 80% were overweight. The public health consequences of the increasing obesity epidemic are discussed, and issues related to the “information gap” about how best to address overweight and obesity in a population-wide basis are discussed.

“Prevalence and trends in overweight among U.S. children and adolescents, 1999–2000” (4). This report used information from the 1999–2002 NHANES survey and compared it with previous NHANES surveys. The methodology was generally similar to the report in the adults. Data reported in this paper come from a survey of 4722 children from birth through 19 years of age. The main outcome measures were the prevalence of overweight among young children by gender, age group, and race/ethnicity. Overweight in age groups 2–19 was defined as being at or above the 95th percentile for the gender-specific BMI used in various age growth charts. The prevalence of overweight was 15.5% among those aged 12–19 years, 15.3% among children aged 6–11 years, and 10.4% among children aged 2–5 years. In comparison with 1988–1994 NHANES 3 data, there has been a 40–50% increase in age-specific obesity. Particularly troublesome has been the very large increase reported in the prevalence of overweight among African-American and Mexican-American adolescents. As was the case in the first paper in adults, the public health issues related to these observations and a variety of other issues of relevance to public health are discussed. Especially worrisome has been the appearance of several “adult” disorders like type II diabetes in adolescents and children.

In the third paper on obesity in the October 9 JAMA, Freedman and colleagues (2) discuss data from the Behavior Risk Factor Surveillance System (BRFSS), a multistage survey that uses random-digit dialing to obtain a representative sample of adults in each state. A brief review of the methods and approach in the BRFSS is presented in the article. Class 3 obesity is defined as a BMI greater than or equal to 40. In 1990, the prevalence of class 3 obesity in the BRFSS was less than 1%. In 2000, it had risen to 2.2%. Class 3 obesity was especially high among African-American women (6%) and individuals who had not finished high school (3.4%). It was also high in individuals who are short. The main conclusion is that these extreme BMI levels are associated with the most severe health complications, and as a result of the large increase in people with class 3 obesity, there will be a huge increase in health care expenditures associated with taking care of these patients. In the final line of this article (2), the authors conclude that “because weight loss is difficult to maintain, the prevention of obesity should be emphasized.”

“Dietary reference intakes for energy, carbohydrates, fiber, fat, protein, and amino acids (macronutrients)” (3). This is an exhaustive report prepared by the Institute of Medicine of the National Academy of Sciences and published by the National Academies Press. It is nearly 1000 pages long and includes a variety of chapters of interest to members of American College of Sports Medicine and the exercise-physiology community in general. Extensive tables and appended material are also included. Of note in this report is chapter 12, “Physical Activity” (3). This is the first time that physical activity has been discussed in great detail in a Food and Nutrition Board (FNB) report. In this chapter, the role of physical inactivity in conjunction with increased caloric consumption in the emerging epidemic of obesity is discussed. This rationale for recommending various levels of physical activity is reviewed, and the positive impact of physical activity and exercise on energy expenditure during and after exercise is highlighted. The impact of physical activity and exercise on body composition is also discussed. The interactions of physical activity, body composition, and health are reviewed. It should also be noted that this report recommended that as much as 60 min of moderately vigorous activity·d−1 might be needed for individuals to maintain ideal body weight (here defined as a BMI < 25). The report noted that these levels of physical activity are generally higher than recent Healthy People 2020 recommendations and other ideas emanating from various advisory bodies. The rationale for this increased recommendation appears to be the realization that Americans as a whole are far more sedentary than previously believed and are consuming calories at a quantity far in excess of their daily physical activity levels. This imbalance is resulting in an epidemic of obesity and metabolic diseases noted both in the FNB report and the articles above. Additionally, the FNB report notes the positive effects on physical activity in individuals who are also overweight. As noted previously and in earlier “News Briefs, ” modest levels of physical activity in otherwise overweight individuals can reduce the burden of obesity-related disease in these individuals and limit the impact of obesity-associated diseases such as hypertension and obesity in overweight subjects.

In summary, the FNB report is to be commended for including physical activity in the obesity equation, providing such a comprehensive review of a variety of issues related to nutrition and physical activity and providing even more evidence that our society as a whole needs to make widespread changes in its dietary consumption and physical activity patterns.


The JAMA papers (1,2,4) and FNB report (3) highlighted in this News Briefs section continue to stress the epidemic of obesity and physical inactivity in our society. Weight loss for those who are obese and overweight can be challenging and difficult to maintain, and more research on this topic at multiple levels is required.


1. Flegal, K. M., M. D. Carroll, C. L. Ogden, C. L. Johnson. Prevalence and trends in obesity among U. S. adults, 1999–2000. JAMA. 2002Oct 9; 288: 1723–1727.
2. Freedman, D. S., L. K. Khan, M. K. Serdula, D. A. Galuska, and W. H. Dietz. Trends and correlates of class 3 obesity in the United States from 1990 through 2000. JAMA. 2002Oct 9; 288: 1758–1761.
3. Food and Nutrition Board, the Institute of Medicine of the National Academy of Sciences. Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Protein, and Amino Acids (Macronutrients). Washington DC: National Academies Press, September 5, 2002.
4. Ogden, C. L., K. M. Flegal, M. D. Carroll, and C. L. Johnson. Prevalence and trends in overweight among U.S. children and adolescents, 1999–2000. JAMA. 2002Oct 9; 288: 1728–1732.
©2003 The American College of Sports Medicine