Increased extracellular water compartment, relative to intracellular watercompartment, after weight reduction

Increased extracellular water compartment, relative to the intracellular wa ter compartment, after weight reduction. J. Appl. Physiol. 87(1): 294-298, 1999. -The hydration of fat free mass (FFM) and extracellular (ECW) and int racellular water (ICW) compartments were studied in 30 obese premenopausal women before and after a 3-mo weight;reduction program and again after a 9- mo weight-maintenance program. Body fat was determined by a four-compartmen t model. Total body water and ECW were determined by deuterium dilution and bromide dilution, respectively. After the weight-reduction period, mean we ight loss was 12.8 kg, and body fat was reduced on average by 10.9 kg. Duri ng weight maintenance, changes in body mass and body fat were not significa nt. Before weight reduction, mean ECW/ICW ratio was relatively high (0.78 /- 0.10). During the the study, total body water and ICW did not change sig nificantly. ECW did not change significantly after weight reduction, but 12 mo after the start ECW was significantly increased by 1 liter. The ECW/ICW ratio increased to 0.87 +/- 0.12 (month 12). The hydration of the FFM incr eased from 74 +/- 1 to 77 +/- 2%; during the weight reduction and remained elevated during weight maintenance. In conclusion, the ECW/ICW ratio and th e hydration of the FFM, did not normalize during weight reduction and weigh t maintenance.