A Statistic Study of Criteria for Judgement of Obesity in School Children by Skinf old Thickness

Abstract

The author studied the skinfold thickness considering the relationship between body heights and the skinfold thickness that is growth, in relation to the method of judging obesity in school children, using the samples consisting of 12, 774 school boys and 12, 032 school girls whose body heights and skinfold thickness (dorsal region of the upper arm +inferior region of the scapular bone) were measured ; and the following conclusions were drawn : 1. The skinfold thickness by the age and the sex increases with advancement of age. However, the skinfold thickness of 12-year-old school boys was smaller than that of 11- year-old boys. 2. The frequency distribution of skinfold thickness by the sex and the age gave a curve with of peaked-topped distribution for the boys, and a curve of plat-topped distributton for the girls, presenting marked distortions. Analysis of the normal distribution of samples from which obesity was excluded by the test of goodness of fit showed no normal distribution of the samples. 3. An attempt was made to, judge obesity in terms of percentiles of the skinfold thickness by the sex and the age, and it was disclosed that the 90 percentile value was applicable for such purposes. 4. Analysis of the mean skinfold thickness by 1-cm intervals of body height gave the following results a : Consideration of the correlation diagrams of the mean skinfold thickness by body heights in the samples aged 6-9 and those aged 10-12 gave the following regression equations: Boys : group aged 6-9: y= +0. 212x - 11. 388 group aged 10-12: y= +0. 150x - 3. 970 Girls : group aged 6-9: y= +0. 209x - 8. 286 group aged 10-12: y = +0. 268x - 17. 491 b : The regression equations for the mean skinfold thickness by body heights in all age groups were as follows : Boys : body heights, 107-145 cm : y = + 0. 1328x - 1. 6523 body heights, 107-155 cm : y=+15. 939 + 0. 135x - 0.014x2 Girls : body heights, 107-145 cm : y= +0. 2056x - 7. 8602 body heights, 107-155 cm : y= +18. 649 + 0. 208x - 0. 0022x2 The correlation coefficient by the primary regression line was not smaller than + 0.9. 6. The standard line for the judgement in screening of obesity was given by the following regression equation: Boys : y= + 0. 3388x - 21. 9429 (M+SD) Girls : y=25, 7150 + 0.3103x - 0.0012x2 (M+SD) This method of judging obesity was called Screening I for Judgement of Obesity. 6. From Brozek's equation for body density and fat amount and from Nagamine's equation for body density and subcutaneous fat was obtained the skinfold thickness corresponding to the body fat amount according to the criteria for judgement of obesity : and utilizing the aforementioned stand regression equation for the skinfold thickness by body heights, the standard line for the judgement of obesity was prepared. This was called Screening II for Judgement of Obesity. 7. The adequacy of the aforementioned two methods for judging obesity was studied, using the values of the skinfold thickness of school children in Warabi-city, which the author measured.