3:23 p.m. | Updated The number of obese New York City schoolchildren fell by 5.5 percent over five years, federal and city officials said Thursday, offering a glimmer of optimism about one of the country’s intractable health scourges.
The decline, documented by annual fitness exams given to most of the city’s kindergarten through eighth-grade students, was the biggest reported by any large city. Over all, the rate of obesity dropped in New York City to 207 children per 1,000 in the 2010-11 school year, down from 219 five years earlier, meaning that 20.7 percent were still considered obese.
“This comes after decades of relentless increases,” Dr. Thomas A. Farley, the city’s health commissioner, said Thursday. While the 5.5 percent drop may seem slight, he said, “What’s impressive is the fact that it’s falling at all.”
The results, published Thursday in a report by the federal Centers for Disease Control and Prevention, showed that the declines in obesity were sharply higher among middle-class children than among poor children. They were also higher among white and Asian children compared with black and Hispanic children, and among very young children — those entering kindergarten or first grade — compared with older children.
Still, the drops held up to some extent across all grades, races and economic levels.
“Because of coordinated, sustained action I am happy to say our children are benefiting from our campaign against obesity, which has plagued communities here in New York and across the nation for nearly three decades,” Mayor Michael R. Bloomberg said.
Mr. Bloomberg said the 5.5 percent drop translated into roughly 6,500 fewer obese children in the public schools. He said that an overwhelming majority of parents think their children are fit and at a healthy weight, but that “the facts tell a different story.”
Dr. Farley attributed the progress partly to the city’s aggressive advertising campaign against sugary sodas, which he said may have altered what parents were providing to their children. The city has also tried to add healthier options to school lunch menus, enacted strict rules on the calorie and sugar content of snacks and drinks in school vending machines, and even put limits on bake sales, a move that caused some grumbling.
Buoyed by the results, city officials also announced Thursday that the restrictions on school vending machines were being expanded to machines in all city buildings, and that they were forming a multiagency task force to recommend further initiatives to combat obesity. Dr. Farley also noted that salad bars were now in cafeterias at many schools, including Public School 218, near Yankee Stadium, where the mayor and the commissioner announced the results at a news conference.
Across the country, recent studies have shown childhood obesity rates remaining flat or slightly increasing. Los Angeles County, which has also conducted a campaign against sugary drinks, had a decline of 2.5 percent during the same period, according to a study by the U.C.L.A. Center for Health Policy Research and the California Center for Public Health Advocacy.
The study was cautious in its language, warning, “A causal relationship cannot be inferred between the fitness interventions implemented by New York City in schools and the decrease in prevalence of child obesity described in this report.” But it said the decreases in obesity “might” indicate that changes in the school or home environment were important.
Obesity experts said that given the stubbornness of the problem, even a small reduction in obesity was an affirmation of public health initiatives.
“We’ve seen nothing but bad news for the last 10 years,” said Marlene Schwartz, deputy director of the Rudd Center for Food Policy and Obesity at Yale University. “I feel like that’s finally starting to turn around.” Dr. Schwartz said younger children, who respond better to adult direction, and children in more affluent families, which have the resources to change, were the easiest to reach, so it was not surprising that they improved the most.
Dr. Farley said the fact that obesity had declined more among younger children was not surprising because it is easier to prevent weight gain than to lose weight. The city has trained 4,000 elementary school teachers to provide in-class physical activity breaks, the study said, and has tried to limit video and TV time in child care programs.
The decline in obesity was documented by the city in FitnessGrams, annual physical education tests that are now completed by most of the city’s kindergarten through eighth-grade students.
Adult men and women are considered obese if their body mass index is 30 or higher, but children are calculated differently because of their constant physical changes. A 7-year-old boy, for example, who is 3-foot-9 would be considered obese with a body mass index of 19.4, or a weight of 56 pounds. A 12-year-old girl who is 5-foot-2 is considered obese with an index of 25.2, a weight of 138 pounds.
By age group, the decline was highest among 5- and 6-year-olds, at 9.9 percent. By race, the drop was highest among white children, at 12.5 percent, and Asian children, at 7.6 percent, and lower for Hispanic children, at 3.4 percent, and black children, at 1.9 percent.