School lunch program can reduce obesity among teenagers, especially those from lower socioeconomic backgrounds

A new study led by Professor Sayaka Nakamura from Sophia University in Japan and Professor Shiko Maruyama from Jinan University in China published in the journal Health Economics reveals the significant positive impact of the Japanese school lunch program on the weight of early teenagers.

The research, titled “Wholesome Lunch to the Whole Classroom: Short- and Longer-Term Effects on Early Teenagers’ Weight,” found that the program effectively reduces body mass index (BMI), percent overweight (POW), and obesity rates, particularly among students from lower socioeconomic backgrounds.

Child obesity is a growing public health crisis worldwide. In response, many countries have implemented school nutrition reforms. This study offers a unique opportunity to evaluate the direct effect of a universal school lunch program by examining data from Japan, where all children attending schools providing lunch are required to participate. This differs from programs in countries like the UK and the US, which often have eligibility criteria.

The researchers employed a rigorous difference-in-differences (DID) analysis using data from the National Nutrition Survey (NNS) spanning from 1975 to 1994. This method compared changes in weight among students in municipalities with and without universal junior-high school lunch programs. The study also utilized propensity score weighting and various falsification tests to ensure the reliability of its findings.

Key findings of the study include:

• Significant reduction in BMI, POW, and obesity: The study provides robust evidence that the provision of school lunch leads to a decrease in BMI, percent overweight, and overall obesity among early teenagers.
• Stronger effects for lower-SES children: The positive impacts of the school lunch program were found to be more pronounced for children from lower socioeconomic backgrounds, including those with non-white-collar fathers and those from households with low expenditure. This highlights the program’s potential to mitigate health disparities.
• No significant impact on underweight students: The research found little evidence suggesting that school lunch reduces underweight among students.
• Cost-efficiency: Despite some criticisms regarding costs, the study’s calculations indicate the cost-efficiency of the Japanese school lunch program in preventing obesity.

While the direct weight reduction effect appears to wane after students graduate from junior high school, the study’s findings underscore the significant short-term benefits of universal school lunch programs in addressing child obesity, especially for vulnerable populations.

These results have important implications for policymakers considering strategies to improve child health and reduce socioeconomic inequalities.