PURPOSES: This experimental study was designed to verify the effect of inhalation of essential oils on body weight, feed intake, food efficiency rate and serum leptin. METHODS: The subjects of this study were 90 growing SD rats (46 males and 44 females). They were allocated into one of four groups, the Fennel group, Patchouli group, Bergamot group and control group. The experimental treatment was the inhalation of aromatherapy essential oils which was applied two times a day for 10 minutes each during 8 weeks. To evaluate the effects, body weight, feed intake, food efficiency rate and serum leptin were measured before and after the treatment. The collected data was analyzed by repeated measures of Kolmogorov-smirnov test and Normal Q-Q plot for nomality, Kruskal Wallis test and X2-test for experimental effects with the SPSS program. RESULTS: The food efficiency rate was significantly lower in the Patchouli group and Fennel group than in the Bergamot group and control group (P=.000). No significant group effects were found for SD rat's body weight, feeding amount and serum leptin. CONCLUSION: In conclusion, these findings indicate that the inhalation of essential oils could be effective in lowering the food efficiency rate rather than the feed intake.