To do this, they measured changes in obesity from 2013 to 2019 among 3,531 California schools in poorer communities. The researchers used over 3.5 million body mass index (BMI) measurements of students in fifth, seventh and ninth grade that were taken yearly and combined at the school level. BMI is a measure of body fat based on height and weight. The researchers looked at differences between schools that participated in the program and eligible schools that did not. They followed the same schools over time, comparing obesity among students before and after the policy change. The researchers found that schools participating in the CEP program had a 2.4 percent reduction in levels of obesity in students compared with eligible schools that did not participate in the program. Localio and Jones-Smith wrote that even small improvements in obesity levels are notable because effective strategies to reduce obesity at a population level remain elusive.

They added that because obesity affects poor and minority children more than others, this policy could help to reduce health inequalities. The CEP likely reduces the amount of obesity by substituting up to half of a childs weekly diet with healthier food, the research found. Research has shown that school meals can be healthier than meals from other sources, including meals at home. One study found that school meals provide the best diet quality of any major U.S. food source. At the same time, the free meals save about $4.70 a day per child or $850 per year. For low and middle-income families, this could result in savings that can be used for other healthy goods or services. Expanding access to school meals Childhood obesity has been increasing over the past several decades. Obesity often continues into adulthood and is linked to many health conditions and early death.

Growing research shows the benefits of universal free school meals for the health and well-being of children. Along with the study of California schools, other researchers have found an association between universal free school meals and reduced obesity in Chile, South Korea and Britain. Studies have also linked the CEP program to improvements in school performance and reductions in suspensions. Universal free meals policies may slow the rise in childhood obesity rates, "but they alone will not be enough to reverse these trends, Localio and Jones-Smith say. Alongside free meals, identifying other strategies to reduce obesity among children is necessary to address this public health issue, they say.