Most Americans Overweight, and One-Third Are Obese: NHANES

January 13, 2010

January 13, 2010 (Hyattsville, Maryland) — Two new studies this week draw attention to the alarming number of individuals in the US considered overweight or obese [1,2]. Based on the latest surveys, more than two-thirds of US adults are overweight or obese, one-third are considered obese, and more than 10% of children and adolescents are also considered too heavy for their age.

The good news, however, is that the increasing obesity trends observed over the past decade appear to be leveling off, according to investigators.

"The levels are still very high, and obesity is a significant health concern," Dr Cynthia Ogden (Centers for Disease Control, Hyattsville, MD), an investigator on both studies, told heartwire . "On the other hand, we've seen a slowing down, if you will, in the rate of increase compared with what it was in the 1980s and 1990s, so that's a positive thing. But the prevalence remains very high, and significant disparities remain, and we did see an increase within this 10-year period. It's not as if there were no increase."

The data, from analyses of the National Health and Nutrition Examination Survey (NHANES), are published online January 13, 2010 in the Journal of the American Medical Association. In an editorial accompanying the studies [3], Dr J Michael Gaziano (Brigham and Women's Hospital, Boston, MA) argues that the despite the leveling off, the magnitude of the obesity problem threatens to undo gains made in recent years.

"Despite the many advances in preventive medicine and treatment that reduced cardiovascular disease, the new stage of the epidemiologic transition, the age of obesity and inactivity, emerged to threaten the progress made in postponing illness and death to later in adult life spans," he writes. "The steady gains made in both quality of life and longevity by addressing risk factors such as smoking, hypertension, and dyslipidemia are threatened by the obesity epidemic."

Two-Thirds of US Adults Obese or Overweight

Speaking with heartwire , Ogden, the first author of the study investigating trends in the prevalence of high body-mass index (BMI) in children and adolescents and an author, along with lead investigator Dr Katherine Flegal (Centers for Disease Control, Hyattsville, MD) of the study in adults, said NHANES provides enough data every two years to examine the natural prevalence of obesity in the US population. The purpose of these studies was to document trends over two-year periods for the past 10 years.

In the first study, they analyzed the prevalence of obesity and overweight in 5555 adult men and women based on height and weight measurements used to calculate BMI. Overweight was defined as a BMI of 25.0 to 29.9 kg/m2 and obesity defined as a BMI >30.0 kg/m2.

In 2007–2008, the overall prevalence of obesity was 33.8%, with more women than men, 35.5% vs 32.2%, considered obese. Combining obesity and overweight, the overall prevalence was 68.0%, this time with more men than women, 72.3% vs 64.1%, considered overweight and/or obese. The prevalence of obesity varied by age group and by racial and ethnic groups.

Prevalence of Obesity and Overweight (%) for Adults >20 Years

Category All (n=5555) Non-Hispanic white (n=2618) Non-Hispanic black (n=1114) All Hispanic (n=1566) Mexican-American (n=945)
BMI >30 33.8 32.4 44.1 38.7 40.4
All men 32.2 31.9 37.3 34.3 35.9
All women 35.5 33.0 49.6 43.0 45.1
BMI >25 68.0 66.7 73.8 77.9 78.8
All men 72.3 72.6 68.5 79.3 80.0
All women 64.1 61.2 78.2 76.1 76.9

Over the 10-year period, however, the prevalence of obesity did not significantly increase for women. There was a significant linear trend for men in the prevalence in 2007–2008 compared with the prevalence in 1999–2000, but the most recent figures were not statistically different when compared with data in 2003–2004 and 2005–2006.

In the second NHANES analysis, 11.9% of children and adolescents aged two to 19 years were considered obese, in this case defined as being at or above the 97th percentile of the BMI-for-age growth charts. Using less stringent definitions, 16.9% and 31.7% of the kids were at or above the 95th and 85th percentile of the BMI-for-age growth charts. Like adults, disparities existed by age and by race and ethnic groups.

"In children, we saw no change over the 10-year period except for in boys six to 19 years of age," noted Ogden. "Here we saw an increase among the heaviest boys, among a cut point that is usually heavier than what we use to determine obesity. For those kids, the prevalence did increase, so there is a suggestion that the heaviest kids are getting even heavier. There is definitely still a concern."

Statistics Are Still Staggering

In his editorial, Gaziano writes that while a slowing of the steady upward trend in overweight and obesity is good news, "the statistics are still staggering," given that most Americans are overweight and one-third are obese.

The results of the survey are sobering, "given the wide variety of deleterious health effects strongly linked to excess weight," such as coronary heart disease, ischemic stroke, hypertension, dyslipidemia, type 2 diabetes, joint disease, cancer, sleep apnea, asthma, and other chronic conditions. Early obesity, he notes, strongly predicts later cardiovascular disease, and excess weight might help explain the dramatic increase in type 2 diabetes, a major risk factor for cardiovascular disease.

"If left unchecked, overweight and obesity have the potential to rival smoking as a public-health problem, potentially reversing the net benefit that declining smoking rates have had on the US population over the last 50 years," writes Gaziano.

Unlike smoking, high blood pressure, and dyslipidemia, however, the best approach to treating overweight and obese individuals is still unknown. The current approach involves changes in lifestyle, but as most clinicians are aware, promoting lifestyle changes to encourage weight reduction has been disappointing, according to the editorial. Still, given the risk of obesity-related health concerns, a massive public-health campaign to raise awareness about the dangers is needed, and the longer the delay in doing so increases the likelihood of negating the significant progress achieved in decreasing chronic disease in the past four decades, writes Gaziano.

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