Very-low-calorie diets (VLCDs) provide a rapid decrease in total body weight, but limited data are available regarding the extent of fat loss and whether body fat distribution is altered. The purpose of this study was to investigate body composition, body fat distribution, and resting metabolic rate in obese men and women and to compare bioelectrical impedance analysis (BIA) with hydrodensitometry before and after 12 weeks of treatment in a VLCD program. Body composition was assessed by hydrodensitometry and BIA. Circumference measures were used to determine waist:hip and waist:thigh ratios. Seventeen subjects lost a mean of 24.2 kg. A mean of 75.5% of the weight loss was adipose tissue as measured by hydrodensitometry. BIA underestimated body fat percentage compared with hydrodensitometry in this obese population. Waist:hip and waist:thigh ratios showed a small but significant decrease, implying a decreased risk for diabetes and cardiovascular disease after weight loss. Resting metabolic rate, as measured by oxygen consumption, dropped 23.8% during the 12 weeks of the VLCD. The findings indicate that a VLCD can provide a rapid weight loss of more than 75% fat and a concomitant decrease in waist:hip and waist:thigh ratios. The findings also indicate that BIA may not be a useful tool in assessing fat loss in obese subjects. Finally, it appears that the decrease in resting metabolic rate that occurs during treatment with VLCD does not correlate with changes in lean body mass.