Background. Improving insulin sensitivity in coronary artery bypass grafting patients may translate into improved glycemic control and postoperative outcomes. Hypothesis. A short-term low glycemic index (LGI) diet will reduce postoperative insulin resistance. Methods. Preoperative consumption of a high glycemic index (HGI) (5) or LGI (6) diet 3-weeks preoperatively. Outcomes, including insulin sensitivity (SITT, HOMA), were measured at baseline, preoperatively and postoperatively. Results. Substitution of HGI or LGI foods resulted in an average 8.6 unit increase, or 11.0 unit decrease, respectively in glycemic index. Insulin sensitivity improved significantly in the LGI group preoperatively compared to the HGI group using the HOMA (P=0.018). Insulin sensitivity was significantly reduced postoperatively in both groups, but no significant difference was found between them. There was a trend in the LGI group towards improved glycemic control and worse outcomes; which requires further investigation. Summary. A preoperative LGI diet presents a non-invasive cardio-protective opportunity warranting clinical trial.