[Energy expenditure at rest and body composition in obese subjects before and after weight loss].

In 7 obese subjects (3 males and 4 females), before (T0) and after (T60) weight loss, and in 10 nonobese subjects (4 males and 6 females) as controls, resting energy expenditure (REE) and body composition were evaluated. In obese subjects fat-free mass (FFM) and fat mass (FM) were significantly reduced after weight loss. REE, expressed in absolute value, was significantly higher in obese subjects at T0 with respect to controls (1683 +/- 77.3 vs. 1425 +/- 70.5 Kcal/day; p less than 0.05); in obese group REE was significantly lower at T60 (1563 +/- 63.5 Kcal/day) than at T0 (p less than 0.01). The decrease in REE observed in the obese group after weight loss was related only to the loss of FFM (r = 0.88; p less than 0.01). REE, expressed in relation to FFM, was not different between control and obese subjects at T0 (28.64 +/- 0.42 vs 26.40 +/- 1.08 Kcal/Kg-FFM/day; pns); however, this value was significantly lower in the obese group at T60 (25.99 +/- 1.07 Kcal/Kg-FFM/day) with respect to controls (p less than 0.05). It is concluded that a reduction in REE, due at least in part to the loss of FFM, may contribute to the difficulty in the maintenance of body weight often observed in obese subjects after a period on hypocaloric diet.