Age changes in body composition revealed by computed tomography.

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.