Nobuo Kiriike Department of Neuropsychiatry, Osaka City University Medical School, 1-5-7 Asahi-cho, Abeno-Ku, Osaka City, Osaka 545, Japan.
The height, weight and body mass index (BMI) of Japanese males and females aged from 6 to 24 years between 1960 and 1995 were studied. From 1960 to 1995 in males of all ages and in females aged 6–14 years height, weight and BMI increased. In females aged 15–24 years, the height increased and the weight slightly increased, but the BMI gradually decreased from 21.5 in 1960 to 20.5 in 1995. Over the last 35 years adolescent and young adult women have become thinner. Dieting to be slim has become much more prevalent among young women. These findings suggest that young females in Japan have decreased their BMI by dieting in order to become slim. If this tendency persists, with regard to a close relationship between restrained eating or dieting and eating disorders, Japanese young women have a much greater risk of developing eating disorders.
In Japan anorexia nervosa has been increasing in the clinical setting,1–3 while bulimia and bulimia nervosa have been receiving greater attention in both the clinical setting4, 5 and by the non-clinical populations.6 The prevalence of binge eating and bulimia nervosa has been comparable with that reported in Western countries.7, 8 It has been suggested that eating disorders have been associated to sociocultural factors such as unrealistic expectations of thinness as a symbol of beauty and success, the changing female role and social standards, and attitudes toward obesity. Of these sociocultural factors, unrealistic expectations of thinness can lead to extreme dieting despite biological needs. In Japan, during the last 35 years, a slim body has become increasingly desirable for young women as a symbol of beauty and success as well as in Western countries. Advertising, fashion and films are dominated by this feminine ideal. Therefore, dieting to be slim has become much more common among young women in Japan. It is interesting to identify serial changes in body shape. We examined changes in weight, height and body mass index (BMI) of young females and males between 1960 and 1995 in Japan.
SUBJECTS AND METHODS
The mean body height and weight of males and females aged 6–24 years between 1960 and 1995 in Japan were obtained from the Ministry of Health and Welfare in 1962, 1972, 1982, 1992 and 1996 in Japan.9 The BMI was calculated by the body weight (kg) divided by height (m2).
The serial changes in the mean height, weight and BMI of males aged 6–24 years in each 10 year period from 1960 to 1990 and in 1995 are shown in Fig. 1. The mean height, weight and BMI gradually increased in each 10 year period from 1960 to 1990 with a transient decrease in the BMI of males between 1970 and 1980. There were further increases in 1995. Serial changes in the mean height, weight and BMI of females aged from 6 to 24 years in each 10 year period from 1960 to 1990 and in 1995 are shown in Fig. 2. The height and weight of females aged 6–24 years increased in each 10 year period between 1960 and 1990 and in 1995. The weight of females aged 15–24 years increased slightly during this period, but the increase was not as great as that observed in males. Thus, the BMI in females aged 15–24 years had decreased from 21.5 in 1960 to 20.5 in 1995.
In this study, height, weight and BMI increased in males aged from 6 to 24 years and in females aged from 6 to 14 years between 1960 and 1995. In females aged from 15 to 24 years, height increased and weight slightly increased, but BMI gradually decreased from 21.5 in 1960 to 20.5 in 1995. During the last 35 years adolescent and young adult females have become thinner. The main cause of the decreased BMI was that weight did not increase in proportion to the increase of the height (Fig. 2).
Body weight is regulated with the balance between food consumption and energy expenditure. It was reported that the total food energy for civilian consumption per capita per day decreased slightly between 1960 and 1994 (2096 Kcal and 2023 Kcal, respectively). The total intake of carbohydrates for an adult person per day has decreased significantly from 399 g in 1960 to 282 g (71%) in 1994 mainly due to decreased consumption of rice (carbohydrate rich), while the total intake of protein and fat has increased gradually during this period.9 Although there are no available data on food consumption, especially in young females, it is generally believed that young females ate much less rice than adults because of dieting to be slim or Westernized eating habits. During the last 35 years, a slim body has become increasingly desirable for young women as a symbol of beauty and success in Japan. Advertising, fashion and films are dominated by this feminine ideal. Dieting to be slim has therefore become more common among young women in Japan. The results of our study suggest that the BMI of adolescent and young adult females has decreased and that body shape has become thinner as a result of dieting in order to become slim.
In Japan, eating disorders have been increasing mainly among females during adolescence or early adulthood. Suematsu et al.1 assessed the prevalence of anorexia nervosa by sending questionnaires to 1030 representative institutions throughout Japan. The data were collected from 315 (30.6%) of these institutions. In 1981, 940 outpatients and 372 inpatients had been diagnosed to have anorexia nervosa. This number was twice as high as the number reported in 1976. In 1993, Inaba et al.2 estimated the prevalence of anorexia nervosa by surveying 5057 physicians throughout Japan. Responses collected from 1892 (37.4%) physicians indicated that there were 2685 patients with eating disorders (anorexia nervosa, 1289; atypical anorexia nervosa, 397; bulimia nervosa, 667). The estimated incidence was 14.8 per 100 000 for anor- exia nervosa and 6.7 per 100 000 for bulimia nervosa among 10–29 year old females. Since 1980, in Japan, the number of patients with anorexia nervosa, as well as bulimia nervosa, have increased remarkably. Since 1980, many investigators have studied the prevalence of anorexia nervosa in adolescent girls in non-clinical settings using self-report questionnaires in various areas of Japan. Inaba et al.3 summarized approximately 20 epi- demiological studies reported between 1981 and 1985, and found that the prevalence for anorexia nervosa ranged from 4 to 240 per 100 000. These figures are lower than those reported in the United States of America and other Western countries, but are strikingly higher than those reported in other Asian countries.10, 11
Nogami et al.6 assessed the prevalence of binge eating among 1250 female students using a three-factor eating questionnaire.12 Binge eating was noted in 1.3% in female high school students, 4.0% in college, 2.6% in nursing school, 1.8% in the nutritional department, and 14.2% in the physical education studies. Binge eating was most prevalent among gymnasts and there was a close association between severe weight control and binge eating. Kiriike et al.7 surveyed binge-eating and bulimia among 220 women at a nursing school and 236 women at a junior college. The prevalence of binge-eating more than once a week, together with self-induced vomiting or purgative use, was 3.6% in nursing school students, 2.1% in college women, and 2.9% in the total sample. These women appeared to meet both DSM-III criteria for bulimia and Russell’s criteria for bulimia nervosa. In 1993, Takeda et al.8 reported that the prevalence of bulimia nervosa according to DSM-III R criteria was 0.7% in male students and 1.9% in female students. These data suggest that the prevalence of bulimia nervosa among young women in Japan is similar to that reported in Western countries.
Although the causal relationship between dieting and eating disorders has not been fully elucidated, dieting is often observed in the initial stage of anorexia nervosa or bulimia nervosa. It has been reported that individuals with the tendency to control food intake in order to prevent weight gain or to promote weight loss are likely to overeat under a condition that is antagonistic to self-control. This phenomenon is referred to as counterregulation and regarded as an experimental analogue of binge eating.13, 14
It is therefore, considered that dieting in order to be slim is a common cultural factor that increases eating disorders among young women in Japan as well as in Western countries. With respect to the decrease in BMI in young females, we are concerned that there will be a further increase in the prevalence of eating disorders in Japan.