Sexual Dimorphism in Body Composition in Brazilian School Children from 1979/80 to 1993/94

Abstract

Nutritional stress can be seen in several catastrophic events like wars and when socio-economic differences are very important. Nutritional stress can affect growth and development, changing body composition and minimizing sexual dimorphism. Background: The purpose of this study was to evaluate sexual dimorphism in BMI, upper arm circumference (UAC), upper arm fat area (UAFA), and upper arm muscle area (UAMA) in school children from Paulnnia, Sγo Paulo, Brazil between 1979/80 and 1993/94, periods in which the city had good development, low under nutrition rate and positive growth secular trends. Material and methods: BMI, UAC, UAFA and UAMA were calculated for 2098 children (age range 6.5 – 10.5 yr; 540 (310M:230F) in 1979/80 and 1558 (865M:693F) in 1993/94. Sexual dimorphism was measured by relative differences between means with the formula: DS = (50*(x1-x2)) / (x1+ x2) (SD1+ SD2), where: x1= mean for males, x2= mean for females, SD1= standard deviation for males and SD2= standard deviation for females. Results: Sexual dimorphism showed similar BMI, but UAC and UAFA that were higher in boys in the first study became lower in the second one. These changes were more significant in UAFA. UAMA data were similar in both sexes in the first study and became higher in males in the second one. Conclusions: These trends showed a recovery in sexual dimorphism. Girls recovered fat mass and boys got muscle mass in a lower degree.