Regional changes in body composition by time of year in healthy postmenopausal women.

We examined regional changes in fat, lean, and bone tissue for greater than 1 y in 125 postmenopausal women. Duplicate whole-body scans were performed at 6-mo intervals. Period 1 was June or July to December or January and period 2 was December or January to the following June or July. Lean and bone tissue mass in the arms, legs, trunk, and whole body increased in period 1 and decreased in period 2 [eg, lean tissue in legs increased 1.84 +/- 0.41% (mean +/- SE) in period 1 and decreased 2.84 +/- 0.39% in period 2, P less than 0.001]. In each region except the arms, fat tissue decreased in period 1 and increased in period 2. Quadriceps muscle strength was correlated with lean tissue mass of the legs [rp (controlled for height) = 0.24, P V 0.02] and physical activity was correlated with quadriceps strength. Overall, body weight did not change significantly (0.17 +/- 0.41% increase, P greater than 0.20); however, there was a net loss of 1.08 +/- 0.39% (P less than 0.01) in lean tissue in the legs and a net increase of 3.43 +/- 1.12% (P less than 0.01) in fat tissue in the trunk.