Total body water content in normal and grossly obese women

Total body water content was estimated for 27 normal and 27 obese women by an isotope dilution technique using tritiated water. The mean total body water content expressed in absolute amounts was significantly raised in the obese group (P less than 0-001), but was significantly lower (P less than 0-001) when the values were expressed as a percentage of body weight. Significant correlations were found between weight and total body water content (P less than 0-001 and P less than 0-05) for the normal and obese subjects respectively. Separate regression equations based on height and weight were calculated for the normal and obese subjects, and good agreement was found in most instances between the measured and calculated total body water contents. The overweight women, with two exceptions, had total body water values in the expected range, which indicated that they were accumulating fat, not water. Although excess water was found in 2 women, this contributed only about 50% to their overweight.