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Team sports may fight weight problems better than other forms of exercise among high schoolers, researchers found.

Playing in three or more sports per year cut risk of overweight or obesity by 27% compared with no participation (95% CI 0.61 to 0.87), according to results from a longitudinal survey-based study by Keith Drake, BA, of Dartmouth College in Lebanon, N.H., and colleagues.

Walking or biking to school cut risk of obesity but not overweight, while gym class had no impact on weight status, the group reported in the August issue of Pediatrics.

"High school sports participation typically involves regular practices and competitions, leading to consistent moderate to strenuous activity, which may explain the strength of its relationship with weight status compared with other forms of physical activity," they wrote.

At a time when many schools are cutting back on sports over budget concerns, focusing in on what works best is key, Drake's group suggested.

"Increasing opportunities for all adolescents, regardless of athletic ability, to participate in sports should be prioritized for obesity prevention," they argued.

The researchers analyzed data from telephone surveys with 1,718 high school students and their parents as part of a larger 7-year longitudinal study at 26 randomly selected New Hampshire and Vermont public schools.

Among the mostly ninth and 10th graders, 29% were overweight or obese and 13% were obese.

Participation in school sports teams was common:

• 17.4% played on one team over the course of the prior year
• 18.6% played on two teams over the past year
• 35.3% played on three or more sports teams per year

One team sport seemed to help a little, but the impact of sports on overweight or obesity reached significance only with more intensive participation.

Teens in two or more sports in the prior 12 months were 22% less likely to be overweight or obese and 39% less likely to be obese than those who didn't participate (adjusted P<0.05 and P<0.01, respectively).

Those on three or more teams over the same period were 27% less likely to be overweight or obese and 39% less likely to be obese than those not on any sports teams (both adjusted P<0.001).

Active commuting to school by foot or bike also tended to help against obesity, but only reached statistical significance for the 10% of kids who did so on more than 3.5 days a week (adjusted risk ratio 0.67, P<0.05). Active commuting had no impact on combined risk of overweight or obesity.

More frequent walking or cycling other places, playing sports or other physical activity for fun, or having had physical education class in the prior week didn't have an impact on either weight category.

Gym has been shown to help for younger children in prior studies, but "PE classes may not involve a substantial enough duration or intensity level of physical activity to affect overall energy balance in high school students," the researchers suggested.

An attributable risk analysis controlling for all other factors suggested that if all high school students were to play on two sports a year:

• Rates of overweight or obesity would fall by a relative 10%, from 29% to 26%
• Obesity prevalence would drop by 26%, from 13% to 10%

If all adolescents walked or rode their bike to school, the obesity prevalence was projected to decline 22%.

The researchers cautioned that those estimates assumed a causal link between physical activity and weight status. A bigger limitation was the study's reliance on self-reported height, weight, and physical activity.

National rates of sports participation are lower and obesity rates higher than in the cohort studied, the group noted.

"Our estimates of the potential benefit of increasing sports participation would be even higher in areas with lower rates of sports participation and higher rates of overweight/obesity, as in most of the country," they concluded.

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