Study tips: A healthier school lunch can reduce obesity

A 2010 federal law that raised dietary standards for school meals may help slow the rise in obesity among American children — even teens who can buy their own snacks, a new study showed.

The national study found a small but significant drop in the average body mass index of more than 14,000 schoolchildren ages 5 to 18 whose height and weight were tracked before and after implementation of the Healthy, Hunger-Free Kids Act of 2010 .

The study is new evidence that improving the quality of school meals through legislation could be one way to help change the trajectory of childhood obesity, which has been on the rise for decades and now affects about 1 in 5 American children. Whether the program will begin to turn the tide for the entire country, and not just for the groups of children studied, is still unclear. About 30 million children in the US receive school lunches every day.

“You have the potential to really influence their excess weight gain throughout their childhood,” says Dr. Aruna Chandran, a social epidemiologist at the Johns Hopkins Bloomberg School of Public Health. She led the study, which was published Monday in the journal JAMA Pediatrics.

The Healthy, Hunger-Free Kids Act of 2010, championed by former first lady Michelle Obama, was the first state legislation to improve school meals in more than 20 years. It increased the amount of fruits, vegetables and whole grains needed in school meals.

The new study analyzed nationwide data from 50 cohorts of schoolchildren from January 2005 to August 2016, before the law went into effect, and data from September 2016 to March 2020, after it was fully implemented. Researchers calculated children’s body-mass index, a ratio of weight to height.

It found that body mass index for children, adjusted for age and sex, fell by 0.041 units per year compared to before the law came into effect. That equates to about a quarter of one BMI unit per year, Chandran said. There was also a slight decrease in overweight or obese children, the study showed.

One way to think of the change is that for a 10-year-old boy with an elevated body-mass index, the decline would amount to a 1-pound weight loss, Dr. Lauren Fiechtner, director of nutrition at MassGeneral Hospital for Children in Boston, who wrote an editorial accompanying the study.

“This is important because even BMI smoothing over time is likely important,” she said. Keeping children’s weight stable as they grow can help control excess weight.

Previous studies have shown weight-related effects of the federal law in children from low-income families. The new study is the first to find lower BMI in children across all income levels.

At the same time, significant decreases in BMI measurements were observed not only in children aged 5 to 11 years, but also in children aged 12 to 18 years.

“That’s an incredible shift,” Chandran said. “These are children who may have their own autonomy to buy their own snacks.”

The new results come within days of the release of updated school meal standards, including the first limits on added sugars, reduced sodium and increased flexibility for whole grains. Agriculture Secretary Tom Vilsack said the study shows that healthy school meals are “critical to addressing diet-related conditions such as obesity”.

But some researchers cautioned against interpreting the study’s findings too broadly. Some of the children who participated in the study may not have been enrolled in school meal programs, or their district may not have fully implemented nutritional requirements, said Kendrin Sonneville, an associate professor of nutritional sciences at the University of Michigan School of Public Health.

Significantly, measures such as BMI, even when adjusted for children, “should not be used as a measure of health,” she added.

A slight reduction in those measures, she said, “does not tell us whether the health, well-being and food security concerns of children participating in the school breakfast or lunch program have improved.”


The Associated Press Health and Science division is supported by the Science and Educational Media Group of the Howard Hughes Medical Institute. The AP is solely responsible for all content.

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