Malnutrition occurs frequently prior to lung transplantation (LTR), but patients gain weight after LTR. The study aimed to determine the ratio changes of fat-free mass (deltaFFM): changes of body weight (deltaBW) during refeeding. A total of 37 LTR patients were measured for weight and FFM and body fat by bioimpedance analysis at 1 month post-LTR, then annually for 3 years. Linear regressions determined the ratio deltaFFM:deltaBW during refeeding. DeltaFFM was: year- 1=1.822+0.389* deltaBW, r(2)=0.397; yr-2=0.611+0.246* deltaBW, r(2)=0.441; yr-3=-0.17+0.208 * deltaBW, r(2)=0.319. Refeeding during year-1 in thin subjects resulted in a ratio deltaFFM:deltaBW of 0.389, whereas the change in ratio deltaFFM:deltaBW during year- 2 and 3 was 0.246 and 0.208, respectively. Refeeding resulted in a larger ratio deltaFFM:deltaBW in thin subjects versus normal and overweight subjects. Thus, refeeding in underweight LTR patients is geared to normalizing depleted FFM, whereas later FFM gains were similar to FFM gains in normal and overweight subjects.