HARTFORD, CONN. — Middle school students in an urban, low-income school district chose more fruit and threw less food away after policies in the Healthy Hunger-Free Kids Act went into effect, according to a study in Childhood Obesity.

Researchers for the Rudd Center for Food Policy & Obesity in Hartford examined choice and consumption in school meals in the spring of 2012, 2013 and 2014. The percentage of students choosing fruit significantly increased to 66% in 2014 from 54% in 2012. Researchers used consumption to determine food waste. Among students choosing fruit, the mean percentage of fruit consumed rose to 74% in 2014 from 72% in 2012.

The proportion of students who chose a vegetable dropped to 52% in 2014 from 68% in 2012. Among students who chose vegetables, the mean percentage of vegetables consumed rose to 65% in 2014 from 46% in 2012.

The U.S. Department of Agriculture implemented new policies of the Healthy, Hunger-Free Kids Act in the 2012-13 school year, or before researchers collected data in the spring of 2012. The U.S.D.A.’s National School Lunch Program provides subsidized meals to more than 30 million children every day.

“Updated healthy school meal standards were developed based on doctors' recommendations to help ensure our children would be able to get healthy food at school,” said Secretary of Agriculture Tom Vilsack in a March 4 statement. “This new study adds to a growing body of scientific research that shows these standards are working. It is clear that kids are now eating healthier food and throwing less food away. This is good news for parents and teachers, who overwhelmingly support healthier meals because they know kids learn better when they have proper nutrition. For Congress to meddle with doctors' recommendations and go back to less healthy meals now would not be in the best interest of our children.”

Senator John Hoeven of North Dakota on March 2 said he plans to introduce a Health School Meals Flexibility Act that would provide permanent flexibility to school districts in complying with the U.S.D.A.’s school nutrition requirements. The legislation specifically would address sodium and whole grain requirements for lunch and breakfast programs.

The National Institute of Child and Human Development and the Robert Wood Johnson Foundation funded the Rudd Center study, which involved 12 schools in an urban, low-income school district. More than 70% of students in the district qualify for free lunch and 13% qualify for reduced-price lunch.

“It is possible that the new school lunches have been accepted more readily in districts where the majority of the students are eligible for free/reduced lunch because the lunch program is viewed as an integral part of the school,” the researchers said. “It is also possible that low-income students are used to eating the school lunch each day and feel comfortable with the food service in their schools, making them more willing to trust them and try new options.”

Researchers took a photo of the students’ trays with the students’ permission before they began eating. At the end of the meal, researchers collected lunch trays and weighed and recorded each remaining meal component. They photographed the trays at the end of the meal to identify any items that were consumed entirely and left no waste.

Student selection of fruit increased by 9% for each additional type of fruit offered with the meal.

“We found that students enjoy variety and are more likely to choose fruit with each additional option,” the researchers said. “Interestingly, the fruit cup (which includes different types of fruit, such as pineapple, peaches and grapes in water, 100% juice or light syrup) was among the most consumed items.”

Besides fruit and vegetables, researchers also noticed how many entrees and how much milk students consumed. The percentage of students choosing entrees rose to 98% in 2014 from 91% in 2012. Among students who chose entrees, the mean percentage of entrees consumed increased to 84% in 2014 from 71% in 2012.

“Despite concerns that students do not like the new entrees that meet the whole grain and meat/meat alternate regulations, our data show that more students are selecting the entree and they are wasting significantly less because consumption is up to 84%,” researchers said.