Gender dimorphism in size, shape and body composition of child-onset obese and nonobese adolescents

Abstract Gender dimorphism (percent GD) for stature (S), body size, body mass (BM) distribution and body composition for obese and nonobese male and female adolescents (mean age 12.7 years, range 10.5-14.5) was compared for 22 girths, 13 bony widths, five skin + fat folds (SF), fat mass (FM), fat free mass (FFM), body density (Db), and calculated variables (BMI, BSA, unit-size mass, waist:hip ratio (WHR), and FFM/S). BM distribution was computed with the ponderal mass equivalent somatogram. There was significant (P less than or equal to 0.05) percent GD for FM, FFM, Db, for the nonobese, but not obese. Only the neck, forearm and wrist girths revealed small but significant (P less than or equal to 0.05) percent GD for the obese. There was no girth percent GD for the nonobese. The elbow, wrist and ankle diameters revealed significant (P less than or equal to 0.05) percent GD for the obese; there was no significant percent GD for the nonobese for the same bony widths. Only the subscapula and iliac SF revealed significant (P less than or equal to 0.05) percent GD for the obese. For nonobese, percent GD was significant (P less than or equal to 0.05) for the triceps, subscapula and thigh SF, Comparisons between obese and nonobese indicated significant (P less than or equal to 0.05) differences between obese and nonobese males and females for FM, FFM, all girths and SF, but not S. Surprisingly, the obese and nonobese had nearly identical trunk diameters; the sum of biacromion, chest, biilac, and bitrochanter diameters were different by only 4.6 percent (n.s.) for the obese and nonobese males, and 1.3 percent (n.s.) for the obese and nonobese females. Thus, a large central frame-size cannot be used to justify the acquisition or maintenance of a larger than average BM for the obese. The ponderal equivalent analyses revealed that the obese's abdomen was the size of a person projected to have a BM in excess of 100 kg. The use of surface anthropometry in the study of adolescent obesity was supported.