More than 84 million - or 1 out of every 3 U.S. adults - have prediabetes, a condition that if not treated often leads to type 2 diabetes within five years. Average medical expenditures among diabetics are about 2.3 times higher than expenditures for people without diabetes. Physical inactivity and elevated body mass index (BMI) are major risk factors for the disease. Sedentary behavior is becoming increasingly prevalent with the growth of a 'work from home' culture, most recently driven by the COVID-19 pandemic. Cross-sectional epidemiologic data report significant associations between high amounts of sedentary (sitting) time and prevalent cardiovascular disease and diabetes. In our pilot study of 15 subjects with sedentary office jobs, 6 months of sit-stand desk use resulted in a 23% improvement in insulin resistance, most substantial in those who decreased daily sitting by over 90 minutes/day. Additional improvements in vascular endothelial function and triglyceride levels were seen without any change in exercise activity, step counts, or body weight. These findings not only corroborate epidemiologic findings on this topic but suggest causality and warrant a randomized control trial. The investigators hypothesize that adult subjects at-risk for diabetes will improve insulin sensitivity, metabolic and vascular (endothelial) health with a sit-stand desk intervention at work (whether in the office or at home), in the context of a randomized, controlled trial. The investigators will randomize 198 sedentary office workers with a BMI≥25 at risk for type 2 diabetes mellitus in a 1:1:1 ratio of three groups: (a) sit-stand desk intervention targeting 2 hours standing per day; (b) sit-stand desk intervention targeting 3 hours standing per day; or (c) control arm over 6 months. The block randomization design will allow for important dose-response analyses. The investigators will objectively quantify standing time, sedentary time, sedentary bouts, daily steps, and exercise activity times using a compact and re-usable accelerometer that adheres to the subject's thigh. This will provide objective assessments of activity levels and sedentary times for 7 full days each at baseline, 3 and 6 months. The device is equipped with an inclinometer to classify posture (sitting verses standing).