Described herein are methods for improving engraftment of hematopoietic cells in an individual following hematopoietic progenitor cell transplantation (e.g., via bone marrow or cord blood transplantation). Methods for increasing hematopoietic progenitor cell proliferation in individuals with bone marrow aplasia are also described. The methods involve administering an agent that inhibits adipogenesis, adipocyte growth, adipocyte differentiation and/or adipocyte proliferation