The purpose of this study is to determine whether changing the microbial composition in the colon can improve metabolism of sugar in people who are on the verge of developing diabetes (pre-diabetics). Study participants will undergo a fecal microbiota transplantation (FMT) using material from lean donors, as well as a series of tests prior to and after the transplant. The investigators will examine any changes in fecal bacterial composition associated with FMT and determine if any observed changes have an influence on blood sugar metabolism.