Giving students access to cool, clear drinking water at lunch may be helpful in reducing obesity among children and teens, according to a study published in the March issue of JAMA Pediatrics.

The study, which was conducted in New York City’s public elementary and middle schools, found that installing large “water jets” (electrically cooled, large clear jugs with a push lever for fast dispensing) in cafeterias was associated with a small but significant average weight loss among students.

“Water jets could be an important part of the toolkit for obesity reduction techniques at the school setting,” the study’s authors conclude.

Obesity in children is a major public health issue in the United States. Nationwide, about 17 percent of children aged 2 through 19 — about 12.7 million children in all — are obese, according to the latest estimates from the Centers for Disease Control and Prevention (CDC). Being obese puts young people at increased risk of having high blood pressure, bone and joint problems, and sleep apnea, as well as psychological problems such as depression and low self-esteem.

Young people who are obese are also more likely to develop heart disease, type 2 diabetes, several types of cancer, osteoarthritis and other chronic health problems when they become adults.

Study details

The researchers decided to conduct this study after they learned that New York’s Department of Health and Mental Hygiene and Department of Education were going to increase access to drinking water at lunchtime by placing “water jets” in school cafeterias.

Water jets dispense a fast stream of water. Health officials and educators hoped the devices, which cost about $1,000 each, would encourage students to drink water rather than sugar-sweetened beverages during lunch. (High-calorie, non-milk beverages had already been banned from school vending machines.)

Between the school years 2008-2009 and 2012-2013 — the period of the current study — about 40 percent of the city’s 1,227 elementary and middle schools received the water jets, and 60 percent did not.

Using student height-and-weight data collected annually as part of the school system’s physical education program, the researchers calculated the body mass index (BMI) of the 1 million students in all 1,227 schools. They then compared the average BMIs of the children in the schools with water jets with the average BMIs of those without the devices.

Key findings

Those average BMIs were not statistically different before the water jets were placed in the cafeterias. Schools that were about to receive water jets had the same proportion of students who were overweight (39 percent) and obese (21 percent) as those that didn’t receive the devices.

But a difference did emerge after the water jets were installed. The average weight of students in the schools with water jets fell by slightly less than 1 percent in boys and by slightly more than half a percent in girls.

That change may seem small, but it is meaningful, say the study’s authors, particularly given the large number of children who are overweight and obese.

Interestingly, the study also found that students significantly decreased their consumption of fat-free chocolate milk during lunch.

A plausible explanation for this finding, the study’s authors write, “is that some children might not like white milk, and when given the option for chocolate choose that instead. When water is then introduced, they switch away from chocolate milk and toward water.”

That’s a healthful switch. For as the researchers point out, a half pint of fat-free chocolate milk contains about 20 grams of sugar, of which half is added sugar. That’s equivalent to about half of the sugar found in a typical can of soda.

The power of a simple change

This study has several limitations. Most notably, it did not observe who actually used the water in the cafeterias, so it can’t state with certainty that the water was a factor in the average weight loss observed in the students.

Still, the correlation is interesting, and underscores the idea that “sometimes, a very simple intervention can have a powerful effect,” as a commentary that accompanies the study points out.

“At the cost of $1,000 per unit … a school-based drinking water access intervention can be remarkably affordable relative to other, more intensive obesity prevention strategies,” the commentary’s authors add.

FMI: The study is behind a paywall, but you’ll find an abstract on the JAMA Pediatrics website.