Hint of Hope as Child Obesity Rate Hits Plateau
By TARA PARKER-POPE
Published: May 28, 2008
Childhood obesity, rising for more than two decades, appears to have hit a plateau, a potentially significant milestone in the battle against excessive weight gain among children.
But the finding, based on survey data gathered from 1999 to 2006 by the federal Centers for Disease Control and Prevention and published in Wednesday’s issue of The Journal of the American Medical Association, was greeted with guarded optimism.
It is not clear if the lull in childhood weight gain is permanent or even if it is the result of public anti-obesity efforts to limit junk food and increase physical activity in schools. Doctors noted that even if the trend held up, 32 percent of American schoolchildren remained overweight or obese, representing an entire generation that will be saddled with weight-related health problems as it ages.
“After 25 years of extraordinarily bad news about childhood obesity, this study provides a glimmer of hope,” said Dr. David Ludwig, director of the childhood obesity program at Children’s Hospital in Boston. “But it’s much too soon to know whether this is a true plateau in prevalence or just a temporary lull.”
The data come from thousands of 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 American children.
The most recent data is based on two surveys ― one in 2003 to 2004 and one in 2005 to 2006 ― that included 8,165 children ages 2 to 19. In that group, about 16 percent of children and teenagers were obese, which is defined as having a body mass index at or above the 95th percentile on United States growth charts. For example, a 10-year-old girl who is 4-foot-7 would be considered obese if her weight reached 100 pounds. By comparison, about 5 percent of children and teenagers in the United States were obese in the 1960s and 1970s. As startling as those numbers are, the good news is that from a statistical standpoint, obesity rates have not increased since 1999. Estimates for the number of children who fall into the overweight or obese category also have remained stable at about 32 percent since 1999. Overweight is defined as at or above the 85th percentile.
In fact, the number of children who fall into the obese category decreased from 17.1 percent to 15.5 percent between the 2003 and 2006 surveys, but the decline was not statistically significant. So the researchers combined data from both surveys to enhance the statistical strength of the numbers.
The plateau follows years of excessive weight gain among American schoolchildren. For instance, in 1980, 6.5 percent of children age 6 to 11 were obese, but by 1994 that number had climbed to 11.3 percent. By 2002, the number had jumped to 16.3 percent, but it has now appeared to stabilize around 17 percent.
“It doesn’t mean we’ve solved it, but maybe there is some opportunity for some optimism here,” said Cynthia Ogden, the lead author of the journal report and an epidemiologist for the National Center for Health Statistics.
The researchers did not give reasons for the leveling off of childhood obesity rates. One concern is that the lull could represent a natural plateau that would have occurred regardless of public health efforts.
“It may be that we’ve reached some sort of saturation in terms of the proportion of the population who are genetically susceptible to obesity in this environment,” Dr. Ogden said. “A more optimistic view is that some things are working. We don’t really know.”
Data collected from a handful of obesity programs around the country suggest that the trends may be real.
In Somerville, Mass., a communitywide intervention led by nutrition researchers at Tufts University included doubling the amount of fruit served for school lunch, painting crosswalks to encourage walks to school and increasing physical activity in after-school programs.
Last year, the medical journal Obesity reported that during the 2003-2004 school year, Somerville schoolchildren gained less weight than children in nearby communities. The researchers are trying to replicate the program in rural areas in other parts of the country.
In Arkansas, a statewide obesity effort has eliminated vending machines in elementary schools, added a half-hour of daily physical activity to the school curriculum and sent home annual childhood health reports alerting parents about obesity risks. As part of the program, school officials in the past four years have tracked the weight and height of 475,000 children, and those numbers show that average body mass index rates in Arkansas have held steady.
“If the national data are now showing that as well, then probably we’re seeing the early effects of increased awareness and focus,” said Dr. Joe Thompson, a pediatrician and director of the Arkansas Center for Health Improvement, which collects the state’s student body mass index data. “But to achieve a long-term reversal is going to require a comprehensive and coordinated effort to make sure we’re reaching all kids across the U.S.”
One trend that has not changed in the new data are differences in obesity risk based on age and race. Children 2 to 5 were significantly less likely to be overweight compared with adolescents ages 12 to 19. While about 14.5 percent of white adolescent girls were obese, the numbers jumped to 20 percent for Mexican-American teenage girls and 28 percent for black teenage girls.
Among boys, Mexican-Americans were also more likely to have a high body mass index compared with white boys. Despite the differences, obesity rates have also appeared to stabilize among minority children.
One worry is that as obesity rates stabilize, financing for childhood health efforts will wane. In Arkansas, the program was a success but a financial crunch prompted the state legislature recently to cut physical activity programs in seventh through 12th grade.
While the latest data suggest the obesity epidemic may have been contained, researchers say the real question is whether it is possible to reverse the obesity trend among American schoolchildren.
“We still lack anything resembling a national strategy to take this problem seriously,” said Dr. Ludwig, co-author of an editorial accompanying the obesity report. “The rates of obesity in children are so hugely high that without any further increases, the impact of this epidemic will be felt with increasing severity for many years to come.”
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