Sex differences in the distribution of subcutaneous and internal fat.

One-hundred twenty-one male and 93 female subjects, aged 18-23 years, were selected for an investigation of the proportion of subcutaneous to total fat in the whole body. Body fat mass was calculated from body density using the Siri equation. Subcutaneous fat mass was calculated by measuring skinfold thickness at 15 sites and using a modification of the equation derived by Skerjl, Brozek, and Hunt. The main modification to this equation was the introduction of a midlayer area of subcutaneous tissue that is multiplied by fat thickness to give fat volume. The outermost body surface area, which has been utilized in previous research, results in an overestimation of the true subcutaneous fat mass. The average percentages of fat situated subcutaneously (PFSSs) were calculated as 53.7% for males and 62.6% for females. This sex difference is also seen in correlation-regression analysis of PFSS and percentage of fat. In females PFSS decreases with increasing total percentage of fat, whereas in males there is no significant relationship between PFSS and total percentage of fat. This suggests that the proportion of subcutaneous to total fat distribution is negatively related to fatness in females.