Cachexia is characterized by severe weight loss, including adipose and muscle wasting, and occurs in a large percentage of cancer patients. Insulin resistance contributes to dysregulated metabolism in cachexia and occurs prior to weight loss in mice with colon-26 tumor-induced cachexia. Therefore, we hypothesized that the insulin sensitizer, rosiglitazone, would attenuate the loss of adipose and muscle to result in improved outcomes for mice with late-stage cachexia. Male CD2F1 mice were inoculated with colon-26 adenocarcinoma cells or vehicle. Treatments included vehicle, rosiglitazone (10 mg/kg body weight/day) or rosiglitazone plus pair-feeding to food intake of vehicle-treated mice with tumors. Rosiglitazone delayed weight loss onset by 2 d over the 16 d duration of this aggressive tumor model. This finding was associated, in part, with increased food intake. In addition, adipose mass, adipocyte cross-sectional area and inflammation were improved with rosiglitazone. However, at the time of necropsy 16 d after tumor inoculation rosiglitazone had no effect on retention of muscle mass, strength or proteolysis in late-stage cachexia. We did not measure stamina or endurance in this study. In early-stage cachexia, rosiglitazone normalized PDK4 and PPAR-delta mRNA in quadriceps muscle and rescued the decrease in insulin-stimulated glucose disappearance in mice with tumors. Rosiglitazone may delay weight loss onset by decreasing tumor-induced markers of metabolic change in early-stage cachexia. These changes predict for modest improvement in adipose, but no improvement in muscle strength in late-stage cachexia.