Computed tomography (CT) produces thin cross-sectional radiographs that may prove very useful in body composition research. CT images of the abdomen allow computerized measurement of total fat area, and also enable the differentiation of subcutaneous fat from intraabdominal fat. The preset investigation examines whether a single CT scan of the abdomen provides an accurate indication of overall abdominal adiposity. Graphs of measurements from seven sequential scans of the abdomen in eight patients showed that rankings of total abdominal area, total fat area, subcutaneous and intraabdominal fat area are relatively consistent no matter which abdominal level is chosen. Correlations of 0.89 to 0.99 between single scans and the average values for all scans show that a single CT image contains the same information on adiposity as a series of scans. These results suggest that future CT studies of body composition can limit radiation exposure by using single scans at different anatomical sites. If only a single scan at one site can be obtained, the level of the umbilicus may be the most useful, because it contains the largest percentage of fat in the body, and best allows differentiation of intraabdominal from subcutaneous fat.

Computed tomography scans were taken of 21 middle-aged men (M age 46.3 years) and 20 older men (M age 69.4 years) to measure differences in body composition with age. Overall, the older men weighed 8.2 kg less than the middle-aged men, and this difference was primarily the result of their having less lean tissue. Although fat mass was only slightly less in older men, there were clear distributional differences in fat between the age groups. Total abdomen fat area was similar in both groups, although the subcutaneous portion of the abdomen fat was less in the older men, and they had correspondingly greater intra-abdominal fat. Muscle areas of the leg and arm were significantly less in the older men, as were all lean tissues of the abdomen and chest. Analysis of fat accumulation between muscles of the abdomen and leg indicated fat infiltration into lean tissue in the older men. Causes of this apparent fat redistribution and lean body mass decline with age are presently unknown.

Computed tomography (CT) scans were taken of 21 middle-aged men (mean age 46.3 years) and 20 older men (mean age 69.4 years) to measure differences in body composition with age. Overall, the older men weighed 8.2 kg less than the middle-aged men, and this difference was primarily the result of their having less lean tissue. Although fat mass (by whole body potassium counting) was only slightly less in older men, there were distributional differences in fat between the age groups. Total abdomen adipose tissue area (from CT) was similar in both groups, although the subcutaneous portion of the abdomen adipose tissue was less in the older men, and they had correspondingly more adipose tissue within the abdominal cavity. Muscle areas of the leg and arm were significantly less in the older men, as were all lean tissues of the abdomen and chest. When these data were corrected for differences in body weight with age, the results were still significant, suggesting a centripetalization and internalization of fat with age. Causes of this apparent fat redistribution and decrease of lean tissue with age were not revealed by this study and are presently unknown.

Ultrasound (A-scan mode) and skinfold methods were evaluated in the measurement of subcutaneous fat thickness and prediction of total fat weight (by whole body potassium counting). Based on intraobserver correlations on 39 men at 15 body sites, skinfold caliper measurements were more reproducible than ones obtained by ultrasound. Measurements made with the two techniques at the same site typically produced different mean estimates of fat thickness. However, scores were often highly correlated with each other, indicating similar relative rankings of subjects by each technique. Skinfolds were more highly correlated with total fat weight than were ultrasound measurements, but body weight. Anthropometric measurements were highly correlated with fatness because of their association with body weight, and when this relationship was statistically controlled for, they typically lost their predictive effectiveness. Multiple regression analyses revealed that the best predictors of fat weight were body weight along with skinfold and ultrasound measurements. These results suggest that skinfolds are a more effective means of assessing subcutaneous fat than ultrasound, especially when the large difference in cost of equipment is considered.

Computed tomography (CT) scanning was evaluated for its potential application to body-composition research. Three cross-sections (upper leg, abdomen, chest including upper arms) were scanned in 41 healthy men (mean age 57.6 years). Subcutaneous fat thicknesses measured at specific sites on the CT scans were correlated with the total area of fat from the same scans. For the chest and leg cross-sections, correlations were highly significant. Subcutaneous fat thicknesses at the abdomen were relatively poorer correlates of total abdomen fat area, because they were unrelated to intra-abdominal fat. Correlation analyses were performed between fat areas of each cross-section and total fat weight (by 40K counting), and the abdomen yielded the highest correlations. Multiple regression was used to predict abdomen fat area from external anthropometry, and abdomen circumference plus one skinfold provided excellent prediction of total abdomen fat area (R2 = 0.79). Subcutaneous or intra-abdominal fat areas separately were not predicted as well by external measurements. When lean body weight was predicted by multiple regression, leg lean area was the best predictor of any anatomical cross-section.