The legend doesn't give stats for the non-diabetics, but there was no difference between the three diets for FBG, there does not appear to be much difference for HOMA-IR (measure of insulin resistance), but a fasting insulin does appear to have been significantly reduced by LC. I'll leave that result for another post.
Many people believe carbohydrate restriction is superior for treatment of T2 diabetes. Remember, the purple triangles are LC and the orange squares are MDTN. At the 2 year mark the MDTN diet beats LC for all three markers. What MAY be going on is that with improved insulin sensitivity, the MDTN's produced less basal insulin, and the insulin they do produce is "seen" by the liver suppressing gluconeogenesis resulting in lower fasting blood glucose levels. I wish they assessed NEFA's!