New research shows that current nutritional standards are prompting more students to choose healthier lunch items, but are they actually eating better? And what does it all cost?

School lunches aren’t necessarily any tastier, but they are healthier.

That’s the conclusion of a new study published in JAMA Pediatricsthat centered on the Healthy Hunger-Free Kids Act (HHFKA).

In their report, researchers said the HHFKA has helped students make healthier choices, and caused only 1 percent of students to opt out of in school lunch programs.

These assertions, however, were questioned by experts interviewed by Healthline.

The HHFKA updated nutritional standards for the National School Lunch Program and the School Breakfast Program starting in the 2012-2013 school year.

Donna B. Johnson, Ph.D., a researcher at the University of Washington Center for Public Health Nutrition, looked at the nutritional quality of foods students were selecting as well as the meal participation rates in the 16 months before and the 16 months after the HHFKA was enacted.

Her research took place from 2011 to 2014 at three middle and three high schools in an urban school district in Washington State.

Johnson’s team reported that meals served under the new guidelines were higher in nutrients and lower in energy density. The mean adequacy ratio (MAR) went up from an average of 58.7 before the HHFKA began to 75.6 after implementation.

Energy density (those with lower calories per gram) went down an average of 1.65 before the guidelines to 1.44 after implementation.

Meal participation was about the same, going from 47 percent before HHFKA implementation to 46 percent after it was enacted.

Read More: New Healthy School Lunch Rules Stir Controversy »

Does this mean students are actually eating better?

William McCarthy, Ph.D., an adjunct professor at the UCLA Fielding School of Public Health, told Healthline the study was based on food production records and not observations of children eating the meals.

“We therefore don’t know if there was an impact on what students ate, only on what was available for them to select,” he said.

While the results suggest that the HHFKA has improved things, McCarthy said, it would be even better to have evidence that children are consuming the healthier meals.

“I am cautiously optimistic that the HHFKA is having a beneficial effect on students’ nutritional health, but more direct evidence would be nice to have,” McCarthy said.

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The School Nutrition Association (SNA) supports most of the new standards, but the group notes that the rules may have caused some unintended consequences.

Diane Pratt-Heavner, an SNA spokesperson, told Healthline that more than a million fewer students choose school lunches since the new standards went into effect.

Additionally, school meal programs are having a hard time managing higher costs associated with the new standards. Her group is requesting more funding for and flexibility on a few of the guidelines.

Pratt-Heavner said the schools in the study are not representative of national data trends. She said the Washington study is “factually incorrect” in stating the National School Lunch Program reaches more than 31 million students every day.

“That was true before the standards took effect,” Pratt-Heavner said, “but USDA data show that the number began to drop in fiscal year 2012 as schools began to implement the standards.”

The US Government Accountability Office found that participation in the National School Lunch Program went down by 1.4 million children between the 2010-2011 and 2013-2014 school years.

Pratt-Heavner reports U.S. Department of Agriculture (USDA) figures state that schools had to absorb $1.2 billion in costs during 2015 to meet the HHFKA guidelines.

A recent SNA survey showed that meeting HHFKA standards has resulted in financial losses for nearly 70 percent of school meal programs surveyed. According to the survey, fewer than 3 percent found a financial benefit. The survey also found that 58 percent of responding schools saw a decline in school lunch participation.

However, the group isn’t sure what has caused the decline. They just note the decrease has come since HHFKA was instituted.

Read More: Nutritious Food Out of Reach for 20 Percent of U.S. Homes with Children »

Mary Podrabsky, MPH, a co-author of the study, told Healthline that the new standards are working as intended and that students are staying with the school lunch program.

“Schools are serving and students are choosing more nutritious lunches,” she said.

Podrabsky noted that not all schools are implementing the standards in the same way. The Washing district, for example, offered students a salad bar and taste tests to promote new items.

She noted that her report cited two recent studies that found that the HHFKA has resulted in students choosing healthier meals at school and that waste has not increased, which would indicate that they pick healthy items, but don’t eat them.

“Stories about some students throwing away food have been reported for as long as schools have served meals to children — certainly well before the updated standards took effect,” she said.

Podrabsky added that they studied high school students, many of whom can leave campus to purchase other food during their lunch periods.

“If meal participation did not change among older students, we think that’s a powerful statement about acceptance of the healthier foods,” she said.