Various methods to assess lean and fat body masses and abdominal-visceral adipose tissue were compared in 26 obese women on extremely hypocaloric diets. The following anthropometric parameters were measured before and after 15 days of extreme calorie restriction: arm circumference (A), waist circumference (W), hip circumference (H) and thigh circumference (T); W/H, W/T, A/H and A/T ratios; subcutaneous biceps , triceps , subscapular, abdominal and thigh folds; echographic thickness of abdominal muscle-aorta; area of visceral (VAT), total (AT) and subcutaneous adipose tissue measured using computed tomography, lean and fat body masses assessed by impedance measurement. Under standard conditions it was shown that echography, like impedance measurement, was the most useful method for assessing lean and fat body masses in obese subjects, whereas plicometry was not found reliable. On extremely hypocaloric diets, echography is able to assess the variations of lean and fat body masses, whereas impedance measurement overestimated the lean body mass. Localisation indexes of visceral fat based on body circumferences were shown not to be suitable for the evaluation of changes in visceral adipose tissue, at least when these were slight. Echography was also the most useful method to assess slight changes in visceral adipose tissue.