Thinness among young Japanese women

Objectives. We described changes in body mass index (BMI) and the prevalence of thinness among young Japanese women (aged 15-29 years) from 1976 to 2000 by reanalyzing the nationwide data in the National Nutrition Survey, Japan. Methods. We used height and weight data sets for 30903 nonpregnant, non-lactating women during the 25-year period. We calculated the mean values of BMI and the prevalence of thinness for 3 age groups (15-19, 20-24, and 25-29 years of age). Results. Changes in BMI per 10 years were -0.17 kg/m(2), -0.22 kg/m(2), and -0.34 kg/M-2 for each age group, respectively. Extreme thinness (BMI < 17 kg/m(2)) increased from 2.4% in 1976-1980 to 4.2% in 1996-2000. Conclusions. Further studies regarding topics such as increased smoking prevalence are needed to identify the underlying causes of increasing thinness.