Background & objectives: Conjugated linoleic acid (CLA) reduces fat deposition in the body, but the mechanism of action is not clear. The present study was conducted to investigate the effects of CLA on body fat metabolism. Since milk fat is the best natural source of dietary CLA, intervention of non-fat milk constituents on CLA treatment was also investigated. Methods: Diets containing CLA (1%) with or without skim milk powder (SMP) was fed to male Swiss albino mice for 60 days. Adipose depots weight, faecal fat and the activities of selected enzymes of lipid metabolism were determined. Results: The mice on CLA and CLA+SMP diets gained weight similar to those on control diet, despite higher feed intake in the former two groups. Total fat pad mass was significantly (P<0.05) less in CLA group than in control group, and inclusion of SMP in the diet enhanced the fat reducing effect of CLA. Adiposity index was also less on CLA and CLA+SMP diets than on control diet, and CLA+SMP was more efficacious in reducing adiposity index. The weight of liver and spleen was increased by CLA, and this effect was eliminated by inclusion of SMP in the diet. The fatty acid synthase (FAS) activity in liver and retroperitoneal adipose tissue decreased substantially on CLA and CLA+SMP diets compared to that on control diet. Interpretation & conclusions: Our preliminary data show that dietary CLA reduces body fat mass by decreasing fatty acid biosynthesis, and the effect is enhanced by inclusion of SMP in the diet.