In Japan, where the population is aging rapidly, research related to health issues faced by the elderly is gaining attention. In contrast, there appears to be less focus on research about children’s health—such as the impact of women’s employment on the diets and health of children. Awareness of this issue serves as the starting point of my research.

Recently, I published a working paper about the impact of a Japanese school lunch program on the weight of junior high school students. Using the National Health and Nutrition Survey conducted by the Ministry of Health, Labour and Welfare, I used data analysis to verify how the school lunch programs affected the weight of students.

The results showed that school lunch programs significantly reduce obesity in children from households with financial struggles, and that this effect continues for several years after graduating. Besides directly reducing obesity through healthy meals, school lunch programs contribute toward reducing obesity in the long term by encouraging healthy diets.

Aiding international policy discussions regarding improvement in quality of school lunch programs

Research about the impact of school lunch programs on body weight is also being conducted in Europe and the United States. However, in the United States and the United Kingdom, participation in school lunch programs is optional, and subsidies for school lunch programs are limited to children from low-income households. Therefore, it is difficult to examine the impact of school lunch programs on children without bias, and research findings are also mixed.

In principle, the Japanese school lunch program mandates all students at schools participating in the program to eat the provided lunch. This makes it easier to discern the impact of the program on children’s health.

Our findings do not simply back the excellent food education effects of Japanese school lunch programs. As evidence of the positive impact that high quality school lunch programs have on children’s health, the results also have meaning in encouraging international policy discussions.

I also used data—such as from the Ministry of Health, Labour and Welfare’s National Health and Nutrition Survey—to conduct research on the changes in body mass index (BMI). Since the mid-1950s, the BMI of Japanese men across all generations has steadily increased. Conversely, the BMI of women across has steadily decreased.

Outside Japan, in the vast majority of countries BMI keeps increasing for both men and women. Why is it that, in Japan, only the BMI of women continues to decrease? This is a theme that had been neglected in the past.

We find that the gap in BMI trend between men and women in Japan was due to a larger decrease in physical activity level in men than in women. Our findings suggest that this is driven by the decrease in men’s physical labor due to economic development and the weakening occupational gender gap.

Using public data to make clear the issues faced by Japan

In conducting empirical research, it is necessary to have many ordinary people participate in studies without any selection bias. However, this incurs huge costs, and there is also the issue of personal information protection. The standard approach is to use existing data, but in Japan, it is difficult to use public administrative records, and often, survey data—collected by having subjects answer questions—is used.

The use of survey data comes with issues, such as people refusing to participate or answer specific questions, inaccurate responses, and difficulties in conducting follow-up surveys for the same persons. Because some countries allow researchers to use administrative records and others provide better survey data, some Japanese researchers use overseas data. However, this does not divulge the issues faced by Japan.

Economics emphasizes positive analysis that throws light on facts. To thoroughly unravel what is happening now, it is necessary to plan out research methods in detail. Furthermore, presenting previously unknown information as proper research results will lead to more constructive policy discussions. This is the significance of empirical research and its real charm.

The book I recommend

“The Testaments”
by Margaret Atwood, Japanese translation by Yukiko Konosu, Hayakawa Publishing Corporation

This is the sequel to “The Handmaid’s Tale,” a book that depicts women robbed of their rights in a totalitarian state ruled by a cultist group. To escape from control, women collected and analyzed information and sought to convey it to people. Their stance is also applicable to my thoughts about empirical research.

Interviewed: October 2023