Abdominal fat depots measured with computed tomography: effects of degree of obesity, sex, and age.

Computed tomography scans at the level of L4/L5 were analysed in 66 men and 34 women who presented for routine tomography, stratified into different age categories. Areas of intra-abdominal fat and subcutaneous abdominal fat were calculated from the scans. In men and in women the proportion of the body surface as intra-abdominal fat increased with age (in men from 12.4 per cent in the age group less than 40 years to 18.0 per cent in the age group greater than 65 years; in women from 10.5 per cent to 14.7 per cent in the respective age categories). Only in men this increase with age was independent of the degree of obesity. In women younger than 40 years the proportion of intra-abdominal fat did not increase with increasing BMI while it did in older women and men. The proportion of intra-abdominal fat in 7 adolescents appeared to be 5.4 per cent, considerably lower compared to adult men and women. Subcutaneous fat areas increased with the degree of obesity but not with age. From simple anthropometric measurements, the intra-abdominal fat area was best correlated with the waist circumference in all ages (except for women younger than 40 years) while it showed weaker associations with abdominal skinfolds and circumference ratios. Age and BMI explained 68 and 74 per cent of the variance in intra-abdominal fat area in men and women respectively. Waist added 8 per cent to the explained variance in men but nothing in women. BMI and waist circumference showed similar correlations to total, intra-abdominal and subcutaneous fat areas in all age categories whereas correlations of skinfolds with intra-abdominal fat areas decreased with age.