Background: The use of exercise training and supplements is effective in controlling obesity. The present study aimed to assess the effect of eight weeks of exercise training combined with beta‐hydroxy‐beta‐methylbutyrate (HMB) supplementation on insulin resistance and serum lipids in overweight and obese boys.  Materials and Methods: In this randomized clinical trial, 40 overweight or obese boys aged 16-19 years were purposively selected and randomly assigned to four groups of 10, including the combined exercise+ HMB group, the combined exercise+placebo group, the HMB group, and the placebo group. The subjects received 3 grams of HMB daily for eight weeks. The combined exercise was eight weeks and included resistance training (leg press, knee bends, chest press, and rowing machine) and endurance training (running at 70%-75% of maximum heart rate). Before and after the test, blood samples were collected, and Monobind kits were used to evaluate HOMA.IR, HDL, LDL, and TC. Data were analyzed in SPSS software (version 25) using paired t-tests, ANCOVA, and post hoc LSD tests at a significance level of P≤0.05.  Results: The results demonstrated that HOMA.IR, LDL, TC, and HDL values ​​were significantly different between the groups (P=0.001). Moreover, HDL increased significantly in the exercise+HMB and exercise+placebo groups (P=0.001), and HOMA.IR, LDL, and TC decreased significantly (P=0.001).   Conclusion: As evidenced by the obtained results, HMB supplementation combined with exercise resulted in a significant decrease in weight and body mass index. Considering the effect of weight control on HOMA.IR, LDL, TC, and HDL, it seems that exercise combined with HMB supplementation can control these indicators in overweight and obese boys.  Keywords: Combined exercise, HMB supplements, HDL, Insulin resistance, LDL, Overweight and obesity, TC.