The present study aims to consider the effects of age on liver enzyme levels of obese men following 15 weeks of moderate-intensity interval training (MIIT). Ten obese middle-aged persons (aged 55.2 ± 4.31 years; height 171.4 ± 3.59 cm; weight 95.7 ± 14.61 kg; and body mass index [BMI] 32.53 ± 4.59 kg/m²) and 10 obese young adults (age 22.7 ± 1.25 years; height 177.4 ± 3.94 cm; weight 100.7 ± 8.04 kg; and BMI 32 ± 2.39 kg/m²) were enrolled in this study. Interval training was followed by 65 to 75% of VO₂max, 1 set, 2 minutes and seven repetitions, 1 minute rest–relief interval with 50% of VO₂max. Blood sampling was carried out in order to measure aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP). All analyses were conducted by Statistical Package for the Social Sciences (SPSS) software (version 16 for windows). A descriptive statistics including mean and standard deviation was obtained for all parameters. Analysis of covariance (ANCOVA) and test of normality (Shapiro–Wilk test) were used. Paired sample t-test was used to compare the pretest and posttest data in each group. Comparison between middle-aged and young adults has shown that MIIT causes significant increase of ALT levels in young adults. There is no significant difference between middle-aged and young adults on other variables. Also paired sample t-test shows that ALP was decreased in both groups.