Making drinking water more available to children at school may help reduce their risk of becoming overweight, a new study suggests.

In recent years, many schools have moved to ban or cut down on sugar- sweetened sodas and juices, in a bid to curb growing childhood obesity rates.

In the new study, German researchers looked at whether providing elementary schools with filtered water - and encouraging students to drink it - would affect the children’s odds of becoming overweight.

They found that over 1 year, children in schools that promoted water- drinking were nearly one third less likely to become overweight than those in other, nearby schools.

The findings are published in the journal Pediatrics.

The reasons for the benefits are not completely clear. When the researchers surveyed the students about their drinking habits, they found that while water consumption went up over the study period, the children’s intake of sugar-sweetened drinks did not decrease.

It’s possible that the survey did not capture small changes in the children’s beverage consumption, according to lead researcher Rebecca Muckelbauer, of the Research Institute of Child Nutrition in Dortmund, Germany.

On the other hand, she told Reuters Health, water itself may have weight-control benefits. She noted that some studies have shown that general hydration influences metabolism, and that water has “thermogenic” - and thereby calorie-burning - effects.

The current study involved nearly 3,000 second- and third-graders at

32 schools in lower-income areas of two German cities. Seventeen schools were equipped with fountains that provided filtered water, and the students were given reusable bottles so they could have water in the classroom. Teachers also led four prepared lessons on the importance of drinking water.

The remaining 15 schools served as a comparison group.

After 1 year, the researchers found no difference between the average body mass index, or BMI - the calculated ratio of height to weight - the intervention schools versus the comparison schools.

However, students in the former group were less likely to become overweight - suggesting, the researchers say, that the water program was most beneficial to children who’d been on the verge of becoming overweight at the outset.

It’s likely, according to Muckelbauer, that the education component is important to getting children to drink more water. On the other hand, she said, it’s unlikely that simply encouraging students to drink water would be effective without giving them an easy supply of it.

SOURCE: Pediatrics, April 2009.