





●Summary：

‐The average height of Japanese men aged from 20 to 39 year old grew from 1975 to 2016 and the average weight increased for the same period as well. On the other hand, while the height of Japanese women for the same age category increased from 1975 to 2016, the weight did not change like the height did. The reason is the sense of beauty that Japanese women have.

The first figure “Correlation between Height and Weight for Japanese Men (20 to 39 year old)” shows the relation between height and weight for Japanese men aged from 20 to 39 year old. The X axis shows average height and the Y axis shows average weight. The data are average height and weight for Japanese men from 20 to 39 year old from 1975 to 2016.

It’s naturally makes sense that the taller you become, the more weight you gain. The coefficient of determination is 0.85, which is high. There is a clear correlation between height and weight for Japanese young/middle aged men.

In the second figure ”Height and Weight for Japanese Men and Women from 1975 to 2016”, you can see the height and weight for Japanese men increasing from 1975 to 1990 and both lines look flat since 1990.

However, such strong correlation is not seen for Japanese women.

The third figure “Correlation between Height and Weight for Japanese Women (20 to 39 year old)” illustrates the relation between height and weight for Japanese women aged from 20 to 39 year old. Although the R² is 0.85 for Japanese men, the number for Japanese women is only 0.22. The R², coefficient of determination, is basically an indicator of how strong the correlation is between two variables and the higher R² is, the stronger relation the two variables have.

The background of female’s lower coefficient of determination is the sense of beauty that young/middle aged Japanese women have. They have a fear of gaining weight in a way due to their beliefs that gaining weight means losing beauty.

The Japan’s national public broadcasting organization, NHK, did a survey to understand the reason why skinny Japanese women want to lose even more weight. For the reasons, 83% of those women said a better looks and 55% answered a fashion. This obsession to lose weight in young Japanese women has made Japanese women even skinnier and unhealthy. This social background seems to cause the weaker correlation between height and weight for Japanese women.





