The main purpose of this study is to test a culturally tailored lifestyle intervention that incorporates motivational interviewing and is designed to prevent, or delay onset of, T2DM in Mexican Americans with prediabetes. Groups of participants will be randomly assigned to: a) an experimental group that receives a lifestyle program (12 2-hour weekly educational group sessions) that emphasizes preparing and eating healthy Mexican-American foods and increasing physical activity, followed by 14 bi-weekly support group sessions to problem solve remaining barriers to adopting recommended behaviors and 3 booster sessions to enhance maintenance of behavioral changes; OR b) an "enhanced" usual care control group that receives lab results with individualized guidance and referrals. A secondary aim of the study is to examine the influence of genetic variation at selected candidate genes for glucose regulation on response to the lifestyle intervention.