Obese and lean Zucker rats were studied to compare the effects of a 6-week
weight loss regimen (period 1) and a subsequent 4-week weight maintenance period (period 2) on
high density lipoprotein (HDL2, d = 1.063-1.125 g/ml)
cholesterol, plasma, adipose tissue, liver, and total body
cholesterol. The effects of
weight loss were compared with animals not subjected to
weight reduction (control, period O).
Weight loss was achieved by reducing food intake below maintenance levels. Plasma
cholesterol did not change significantly among the three periods in obese and lean rats.
HDL2 cholesterol was higher (P less than 0.05) in obese and lean rats at period 2 compared with the other periods. Adipose tissue
cholesterol (per cell) did not differ among the three periods in obese and lean rats. Liver
cholesterol (milligrams/gram liver) decreased significantly (P less than 0.05) at period 1 and sustained this level at period 2 in lean rats, whereas liver
cholesterol was unchanged among the three periods in obese rats. Carcass
cholesterol (milligrams/gram carcass) in obese rats increased significantly (P less than 0.05) after period 1 and sustained this level after period 2. Carcass
cholesterol concentration was unchanged in lean rats. These data suggest that consideration must be given to homeostatic mechanisms of carcass and liver
cholesterol concentrations in studies examining changes in plasma
HDL2 cholesterol levels.