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The aim of this study was to establish reference values for waist circumference among Japanese youths using the 1978-1981 nationally representative data.Growth charts were derived using Cole's LMS method, which adjusts the waist circumference distribution for skewness and allows waist circumference to be expressed as centile or standard deviation score. The sample population consisted of 19 233 children aged 6-18 years. Waist circumference was measured at the level of maximum waist narrowing in girls and at the level of the top of the iliac crest in boys.Comparison was made between the 1978-1981 and 1992-1994 waist circumference charts, showing a large increase in waist circumference over time; the mean difference was 1.1 and 0.5 SD score units in boys and girls, respectively. Defining cut-offs for central fatness as the 90th and 95th centiles of the 1978-1981 reference, the prevalences in 1992-1994 were, respectively, 42.3% and 25.2% in boys and 19.1% and 10.9% in girls. The corresponding prevalences in 1978-1981 were 10% and 5% by definition.This study showed increasing trends in waist circumference, particularly in boys during the period of the two surveys and that the 1978-1981 charts serve as better baseline references for waist circumference among Japanese youth.

A large incremental increase in BMI indicates excess fat deposition in most children, but the reference values for identifying those at risk for developing obesity have not been defined.To determine the mean and SD of annual incremental change (ΔSDS) in BMI for Japanese school children.A cohort of 669 Japanese children in one private school in Tokyo in whom height and weight were measured annually between 6-17 years of age. Each child's BMI was converted to SDS as based on the 1978-1981 Japanese references for the 12 annual measurements to derive the correlation coefficient, r, between two successive measurements. Using the formula, SD of ΔSDS = √2(1-r), the mean and SD of ΔSDS were obtained.Excess BMI gain was defined in terms of ΔSDS in Japanese children. Annual incremental increase greater than 2 SD of ΔSDS, equivalent to 1-2 BMI units/year for younger children and 2-3 BMI units/year for older children, respectively, indicates rapid increase in body fat in Japanese children.Based on analysis of incremental change in BMI in this cohort, a cut-off has been identified that can be used to identify children at risk for developing obesity.

The obesity epidemic in Japan continues to increase. However, the prevalence and trends of obesity have not explicitly been determined in Japanese children.The study estimated the trend and prevalence of overweight in Japanese school children, 1980-2001.The 2001 cross-sectional national survey on 334,939 boys and 335,204 girls, 5-18 years of age was studied, using the 1978-1981 references. Main outcome measures were proportion of children with BMIor =95th centile and those withor = + 20% excess body weight.The prevalence of overweight increased 2.6 times (5.0% to 12.9%) in Japanese boys and 2.5 times (5.0% to 12.5%) in Japanese girls during the last two decades as assessed by using BMI, whereas the Japanese Ministry of Education, Culture, Sports and Science and Technology reported a much smaller increment in prevalence (5.8% to 9.2% in boys, 5.6% to 8.0% in girls, respectively) using the same data but based on a cut-off value ofor = + 20% excess body weight.Official governmental reports significantly underestimate the current epidemic of obesity in Japan.

The prevalence of overweight among Japanese children and adolescents has steadily increased during the last 20 years. Thus, we utilized the 1978-1981 data collected by the Japanese Ministry of International Trade and Industry to construct reference curves of body mass index (BMI) for contemporary Japanese children and adolescents.BMI reference values were derived using the LMS method as based on height and weight data from the cross-sectional national survey of Japanese children and adolescents conducted in 1978-1981 (14,012 boys and 13 781 girls, aged 1.5-18.5 years).The Japanese BMI reference curves were constructed for clinical use. The centile values at the upper end of the spectrum apparently differed in British, Dutch, Japanese, and US children and adolescents. In contrast, the centile values at the lower end of the spectrum nearly overlapped with each other in the four populations.Overweight is concentrated in a subgroup of children and does not occur across the entire population of British, Dutch, Japanese, and US children, indicating a subgroup of genetically and/or environmentally more susceptible children in each country.

The past decades have witnessed a steady increase in thin body stature associated with unhealthy dieting among Japanese female adolescents. The most recent trends in thinness, however, have not been reported.To describe changes in the distribution of body mass index (BMI) of Japanese female adolescents, from 2003-2012.This study examined BMI distribution changes in 2541 relatively affluent Japanese girls, aged 12.5-17.5 years, during 2003-2012. The 2003 and 2004 data were combined and compared to the combined 2011 and 2012 data. Tukey mean-difference plots were used to study the direction and magnitude of shifts in BMI distributions.Prevalence of thinness (BMI5th percentile of the 1978-1981 references) has progressively increased from 2.0-5.7% in 2003-2004 to 3.5-7.8% in 2011-2012 in Japanese girls. The downward shift in BMI was larger in 12.5-14.5 year olds than in 15.5-17.5 year olds and more prominent in the lower BMI spectrum.The trend towards thinness has continued in Japanese girls during the past decade. The distribution of BMI suggests thinner and younger sub-groups of girls are more susceptible to this trend.

The desire for thin body stature and unhealthy eating behaviours have spread among Japanese boys. The prevalence of thinness in boys is expected to increase; however, recent trends have not been reported.To describe changes in the distribution of body mass index (BMI) of Japanese boys, from 2003 to 2012.BMI distribution changes were studied in 2599 relatively affluent Japanese children and adolescents, aged 12.5-17.5 years, during 2003-2012. The 2003 and 2004 data were combined and compared to the combined 2011 and 2012 data. Tukey mean-difference plots were used to study the direction and magnitude of shifts in BMI distributions.Prevalence of thinness has progressively increased from 2.8-4.7% in 2003-2004 to 5.1-7.6% in 2011-2012 in Japanese boys. Tukey plots showed that the increases in the prevalence of thinness are related to shifts in the entire distribution of BMI in the sample.Thin body stature was documented in increasing proportion of Japanese male adolescents. BMI z-scores decreased across the entire BMI centile spectrums, indicating that the whole school population may be at risk of thinness.

BMI or BMI% adjusted for age has been identified as the optimal measure of short-term adiposity change in kindergarten children aged 29-68 months. The optimal measure of annual adiposity change in older age children, however, has not been determined.To identify the optimal measure of annual adiposity change for Japanese children aged 6-12 years.A cohort of 669 Japanese children in one private school in Tokyo in whom height and weight were measured annually between 6 and 12 years. Each child's annual variability in adiposity was summarized by the standard deviation (SD) of BMI and BMI% adjusted for age, BMI z-score and BMI centile. The SDs were compared in overweight and non-overweight children and correlated with each child's baseline BMI z-score.The within-child BMI, BMI% and BMI centile SDs were significantly different in overweight and non-overweight children, while the BMI z-score SDs were similar in the two groups. Furthermore, the within-child BMI, BMI% and BMI centile SDs were inversely correlated with baseline BMI z-score, whereas BMI z-score SDs were not, with the exception of measurements for grade 1-2 children.The BMI z-score is the optimal measure of annual adiposity change for elementary school children.

Excessive thinness has been glamorized among Japanese adolescent girls, and unhealthy dieting to lose weight has become a popular practice among them. The prevalence of underweight in contemporary Japanese girls in comparison with that of boys, however, remains to be studied.The purpose of this study was to determine the prevalence and trends of underweight in contemporary Japanese teenagers of both sexes using nationally representative cross-sectional data.Underweight was defined as BMI3rd percentile by age and sex of the 1978-1981 reference population as previously reported. These reference values were compared with BMIs of the contemporary population based on the 2001 Cross-sectional National Survey data of Japanese teenagers (215 972 boys and 216 496 girls).The prevalence of underweight was approximately 2-3% in junior high school students of both sexes, 12.5-14.5 years of age, approximately 3% in senior high school students of both sexes, 15.5-16.5 years of age, and approximately 4% in senior high school students of both sexes, 17.5 years of age.The prevalence of underweight decreased among Japanese teenage students of both sexes during the past decades. Female preponderance in the prevalence of underweight was not confirmed.