Overweight and obesity, which have a substantial impact on health in the general population, have similar prevalence in solid organ transplant recipients but carry even more serious ramifications. As this group's use of immunosuppressive medication increases the risk for comorbidities, e.g. metabolic syndrome and cardiovascular disease, the prevention of additional risk factors is vital. This systematic review will be the first to summarize the issue of weight gain, overweight and obesity concurrently within and across solid organ transplantation. The three research questions relating to solid organ transplantation are the following: (1) What are the prevalence and evolution of overweight and obesity from pre- to post-transplant?; (2) Which pre- and post-transplant risk factors are associated with post-transplant weight gain, overweight or obesity? and (3) Which post-transplant patient outcomes and comorbidities are associated with pre- and post-transplant weight gain, overweight and obesity?