Obesity Rates Stall, But No Decline

Obesity Rates Stall, But No Decline

After two decades of steady increases, obesity rates in adults and children in the United States have remained largely unchanged during the past 12 years, a finding that suggests national efforts at promoting healthful eating and exercise are having little effect on the overweight.

Over all, 35.7 percent of the adult population and 16.9 percent of children qualify as obese, according to data gathered by the federal Centers for Disease Control and Prevention and published online Tuesday by The Journal of the American Medical Association. While it is good news that the ranks of the obese in America are not growing, the data also point to the intractable nature of weight gain and signal that the country will be dealing with the health consequences of obesity for years to come.

“We’re by no means through the epidemic,’’ said Dr. David Ludwig, director of the childhood obesity program at Children’s Hospital in Boston. “Children will be entering adulthood heavier than they’ve ever been at any time in human history. Even without further increases in prevalence, the impact of the epidemic will continue to mount for many years to come.’’

The data come from thousands of men, women and children who have taken part in the National Health and Nutrition Examination Surveys — compiled by the National Center for Health Statistics at the C.D.C. since the 1960s — and represent some of the most reliable statistics available on the health of the American public. The most recent findings are based on data collected from 2009-10 that have been compared with previous surveys collected in two-year cycles beginning in 1999-2000.

Although from a statistical standpoint, overall obesity rates haven’t changed in more than a decade, the latest analysis did detect some changes in the prevalence of obesity in certain groups. For instance, men and boys have become fatter since 1999, and so have non-Hispanic black and Mexican-American women. Although those trends were only recently detected in the data, there have been no significant increases in obesity prevalence since the 2003-4 survey.

Nobody knows exactly why obesity rates appear to be leveling off. While it’s possible that public education efforts around healthful eating and exercise have had some effect, it may be that the population has reached a biological saturation point in terms of obesity, and that those most vulnerable have already become obese.

“Until we actually see declines in body mass index we can’t confidently say prevention efforts have succeeded,” said Dr. Ludwig.

Although different data collection methods make it difficult to compare obesity rates around the world, a number of studies in other countries have suggested that the prevalence of obesity is growing more slowly or has hit a plateau. Data from England show that for men the prevalence of obesity was 22.2 percent in 2005 and 22.1 percent in 2009; comparable figures for women were 23 percent and 23.9 percent. Studies in Sweden, Switzerland and Spain have also suggested a leveling off of obesity rates.