Water availability associated with decreased student weight in New York schools

The availability of relatively low-cost 'water jet' machines, which chill and oxygenate the water, was associated with decreased student weight and fewer half-pints of milk purchased per student, according to an article published online by JAMA Pediatrics.

In 2009, the New York City's Department of Health and Mental Hygiene and the Department of Education launched an intervention to increase lunchtime access to drinking water by putting "water jets" in school cafeterias. Water jets are electrically cooled, large, clear jugs that dispense water quickly and cost about $1,000 per machine.

Brian Elbel, Ph.D., M.P.H., of the New York University School of Medicine, and coauthors examined the effect of the water jet initiative on student body mass index (BMI), overweight and obesity. Milk purchases were examined as a potential mechanism for the weight outcomes.

The study included 1,227 New York public elementary and middle schools and their more than 1 million students. Among the 1,227 schools, 483 received a water jet (39.3 percent) and 744 (60.7 percent) did not.

Water jets were associated with a decrease in standardized BMI (0.025 reduction) and a decrease in the likelihood of being overweight (0.9 percentage point reduction) and the likelihood of obesity for boys (0.5 percentage point reduction). For girls, water jets were associated with a decrease in standardized BMI (0.022 reduction) and a decrease in the likelihood of being overweight for girls (0.6 percentage point reduction).

Water jets also were associated with a decrease in the amount of half-pints of milk purchased by students (a decrease of 12.3 per student per year), according to the results.

The study has limitations, including the use of administrative data on water jet delivery so use in the cafeteria was not observed and a lack of data on milk consumption.

"Results from this study show an association between a relatively low-cost water availability intervention and decreased student weight. Additional research is needed to examine potential mechanisms for decreased student weight, including reduced milk taking, as well as assessing impacts on longer-term outcomes. Water jets could be an important part of the toolkit for obesity reduction techniques at the school setting," the study concludes.