The effect of residual rice bran (HDRB), obtained by compression, on the onset of diabetes was evaluated in KK-Ay/Ta mice. The HDRB contained approximately 10% oil. However, the inclusion of HDRB in the diet, at a level corresponding to an ingestable amount of brown rice per day, did not increase the body weight. In mice fed an HDRB diet, the postprandial blood glucose levels reduced significantly, whereas insulin secretion decreased slightly. HDRB also contributed to a decrease in the levels of urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), which is an oxidative stress marker. Thus, the results of our short-term experiment suggest that the intake of HDRB produced by compression, at a level equivalent to the amount of brown rice consumed per day, is effective in controlling the onset of diabetes.