We previously reported that a low versus high glycemic index (GI) diet on a high fat (30% kcal fat) background (LGI and HGI, respectively) significantly retarded adverse health effects in C57BL/6J male mice. The LGI diet enhanced whole body insulin sensitivity and repressed high fat diet-induced body and adipose tissue weight gain, resulting in reduced serum leptin and resistin levels (Faseb J 2009; 23: 1092-1101). How white adipose tissue (WAT) is effected is examined in the present study. We characterized the molecular mechanisms underlying the GI-mediated effects in WAT using whole genome transcriptomics technology. We show that a LGI vs. HGI diet mainly exerts its beneficial effects on substrate metabolism, especially insulin signaling of fatty acid metabolism. In addition, cell adhesion and cytoskeleton remodeling showed reduced expression in line with lower WAT mass, but it might also be due to altered insulin sensitivity. An important transcription factor showing enhanced expression is PPARgamma. Furthermore, serum levels of triglycerides, total cholesterol, HDL- and LDL-cholesterol were significantly reduced by a LGI vs. HGI diet, and muscle insulin sensitivity was significantly increased as analyzed by PKB/Akt phosphorylation. Cumulatively, even though these mice were fed a high fat diet, the low versus high GI induced significantly favorable changes in metabolism in WAT. These effects suggest a partial overlap with pharmacological approaches by thiazolidinediones (TZDs) to treat insulin resistance and statins and plantsterols/stanols for hypercholesterolemia. It is therefore tempting to speculate that such a dietary approach might beneficially support pharmacological treatment of insulin resistance or hypercholesterolemia in humans.