We examined the effect of dietary niacin supplementation on fat mass, glucose control, insulin sensitivity, lipid profile, and adiponectin level in diet-induced obese rats. Twenty-one male Sprague-Dawley rats (n=21) were initially divided into two (2) groups of seven and fourteen rats; the group of 14 rats was fed with a high-fat-diet (HFD) and the other group of 7 rats consumed the control diet. Eight weeks after the diet regimen started, half of the rats from the HFD group were shifted to the niacin-supplemented diet (HFND; 1mg niacin/kg diet) while the remaining rats continued on the HFD for another 6 weeks. Throughout the experimental period, the food intake and body weights were measured and recorded. Thereafter, OGTT and ITT were conducted. Fat pads were excised and weighed immediately. Blood samples were also collected before killing to measure the levels of cholesterol, triglycerides, HDL and LDL. HFD-induced obese rats showed significant increase (P< 0.05) in body weight gain, reduced glucose tolerance, insulin sensitivity and increase adiposity as well as altered lipid profile after 8-week of feeding, compared with the controls. However, niacin-supplemented rats had reduced (P< 0.05) weight gain and/or body weight compared with HFD-induced obese rats even in the absence of a significant difference in the food intake among the groups in the experiment. In addition, the rats showed an improved time-course glucose control, insulin sensitivity as demonstrated by a significantly lower AUC values for the glucose curves. The plasma levels of cholesterol, triglycerides and LDL returned towards control values in rats supplemented with niacin compared with obese rats. The findings suggest that niacin exerts beneficial effect on adiposity, glucose tolerance and insulin sensitivity, plasma lipids, and that it specifically modulates the level of serum adiponectin under obese condition.