BOSTON — New patterns from a study of U.S. students in grades 6 to 10 suggest that public health efforts to improve the obesity-related behaviors of U.S. adolescents may be having some success, according to findings published in the on-line issue of Pediatrics on Sept. 16.

Among the findings were increases in the amount of physical activity, more fruits and vegetables intake, more frequent breakfast consumption and less television watching and fewer sweets and sweetened beverage consumption.

The study, conducted by researchers with the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, Md., examined a nationally representative sample of 35,000 children between the ages of 11 and 16 in 2001, 2005 and 2009.

Physical activity was defined in the study as “any activity that usually increases your heart rate and makes you get out of breath some of the time.” The researchers found that while most adolescents fell short of the recommended 60-plus minutes per day of physical activity, the number of days in which they achieved the 60-minute goal increased over the eight-year study period, to 4.53 days in 2009 from 4.33 days in 2001.

As more time is being given to physical activity, less time is being spent watching television, the study found. In 2009, participants devoted about 2.38 hours per day to television, down from 3.06 hours per day in 2001.

Improvements also were noted in food and beverage consumption trends. Participants were asked how many times a week they usually ate fruits, vegetables, sweets and sweetened soft drinks using a scale of 1 = “never,” 2 = “less than once a week,” 3 = “once a week,” 4 = “2 to 4 days a week,” 5 = “5 to 6 days a week,” 6 = “once a day, every day,” and 7 = “every day, more than once.”

Consumption of fruits increased to an average of 4.91 in 2009 from 4.29 in 2001, while vegetables increased to 4.61 from 4.31 during the same timeframe. Meanwhile, consumption of sweets fell to 4.10 in 2009 from 4.70 in 2001 and consumption of sweetened soft drinks fell to 4.18 from 4.85, the study said.

Positive trends also were noted in breakfast, with participants in 2009 saying they ate breakfast about 3.25 days during the five-day school week, up from 2.98 days in 2001.

“It may be that current public health efforts are succeeding; the trends from 2001 to 2009 are encouraging,” the researchers said. “In contrast with earlier studies, (physical activity) increased and TV, the most prevalent (sedentary behavior), decreased from 2001 to 2009.7. During the same period consumption of fruits and vegetables and frequency of eating breakfast increased, whereas consumption of sweetened beverages and sweets decreased. Yet it appears that the magnitude of these changes in health behaviors were not suf?cient to reverse the trends in weight status; B.M.I. (body mass index) increased from 2001 to 2005. Still, there was no signi?cant increase in B.M.I. from 2005 to 2009, perhaps suggesting that the increase in adolescent obesity observed over previous decades may be beginning to stabilize.”