Summary:Patients with hematological malignancies are well nourished prior to allogeneic hematopoietic stem cell transplantation (HSCT). HSCT and associated complications can affect body composition. The study evaluated crosssectionally the prevalence and longitudinally the changes in lean body mass index (LBMI) in HSCT patients. Patients (n ¼ 82) were classified as normal or low LBMI. Logistic regression analyses were used to estimate odds ratios (OR) for low vs normal LBMI, between healthy volunteers and patients; for limited or extensive vs no chronic graft-versus-host-disease (GVHD); and for decreased (Karnofsky o80) vs normal functional status (480). Patients were significantly more likely to have low LBMI at 6, 12 months, 2-3, 4-6 and 46 years than volunteers. In all, 38% of patients were below pre-HSCT LBMI at 4-6 years post-HSCT. Low LBMI was significantly associated with steroid treatment (OR 2.6, confidence intervals (CI) 1.3-5.2, P ¼ 0.008); limited (OR 5.5, CI 1.7-18.5, P ¼ 0.005) or extensive chronic GVHD (OR 20.3,, Po0.001); and decreased performance status (Karnofsky scores of p80) (OR 2.7, CI 1.3-5.9, P ¼ 0.01). Patients were more likely to have low LBMI than volunteers. Chronic GVHD and low performance status were associated with low LBMI; thus, complications and/or treatment increase the likelihood of low LBMI. Patients with hematological malignancies are usually well nourished at the time of allogeneic hematopoietic stem cell transplantation (HSCT). 1,2 However, nutritional consequences after HSCT have not been well studied. Underweight patients are at increased risk of death in the early post-HSCT period, and nonrelapse mortality is greater for extremely underweight or overweight patients. 3,4 High body mass index (BMI), weight normalized for height, may also affect treatment-related toxicity and mortality. 5 Furthermore, low lean body mass (LBM) has been associated with poor outcome and increased length of hospital stay. 6 Allogeneic HSCT and associated complications, including infections and graft-versus-host-disease (GVHD), can affect body weight and body composition. Immunosuppressive therapy after transplantation has been shown to alter skeletal muscle metabolism. 7 Corticosteroids promote muscle atrophy by increasing the rate of protein catabolism, amino-acid efflux, while simultaneously decreasing the rate of protein synthesis. 8 Thus, treatment and complications following HSCT exert profound negative effects on LBM.As low LBM is associated with poor outcome, the evaluation of LBM and body fat changes in pre-and post-HSCT patients can aid in adapting nutrition policy, for example, nutrition support in malnutrition and food restriction in obesity. 9 Just as BMI is useful in evaluating the excess or deficit in body weight in individuals of different heights, the lean body mass index (LBMI, kg/m 2 ) and body fat mass index (BFMI, kg/m 2 ) are potentially useful in evaluating body composition parameters by effectively eliminating differences in LBM and body fat with height. 10 Height-indepe...