Introduction : The obesity can be a serious problem that frequently induces a great deal of complications. Numerous methods have been applied to control obesity and one of them is aromatherapy. This study is a first attempt to verify the effect of the inhalation of essential oils on the obesity. This study was designed as the animal study, because the human study has many socio-psycho compounding variables. Methods : This study was designed to verify the effect of inhalation of essential oils on the body weight, feeding amount, food efficiency rate and serum leptin of SD rats. The research design is repeated measures over time, equivalent control group pretest-posttest experimental design. The subjects of this experiment were obese SD rats. They were allocated to one of four groups, the Fennel G., the Patchouli G., the Bergamot G. and control G. The experimental treatment was the inhalation of aromatherapy essential oils (Fennel, Patchouli, Bergamot). The experimental treatment was applied two times a day for 10 minutes each during 8 weeks. To evaluate the effect of inhalation of essential oils, the body weight, feeding amount and food efficiency rate was measured every week and serum leptin was measured before and after the experiment. The collected data was analyzed by repeated measures of ANOVA, Greenhouse-Geisser, ANOVA, Tukey, Kruskal Wallis test and χ²- test with SPSS program. Results : The results were as follows. The subjects of this study was 84 obese SD rats(40 males and 44 females). The means of age and body weight in obese SD rats were 30 weeks and 344.6g. The food efficiency rate was significantly lower in the Patchouli group and Fennel group than in Bergamot group and control group(P=.000). No significant group effects were found, but significant time effects were found for SD rat's body weight, feeding amount and serum leptin. Conclusions : In conclusion, these findings indicate that the inhalation of essential oils could be effective in lowering the food efficiency rate. 2)