Background and purpose: Plasma levels of lipid profile is one of the main factors in assessing the risk of cardiovascular diseases. The aim of this study was to evaluate the effect of 8 weeks aerobic training on lipid profile, body fat percentage, body mass index, and maximal oxygen uptake in sedentary overweight females in the morning or evening.

Materials and methods: In this semi experimental study, 36 overweight women (mean age 29.71±3.05 years and body mass index 27.25±1.26 kg) were selected using purposive sampling. They were divided in two exercise (n= 10) and control groups (n= 8). Training program included aerobic exercises at 8 am and 6 pm, three days a week. The target heart rate was 60% maximum heart rate (MHR) for 25 minutes in first week which reached 85% MHR for 45 minutes in last week. To determine the lipid profile, a 12 h fasting blood sample was taken before and after the intervention.

Results: The results showed that following training in both morning and afternoon, HDL-c levels increased significantly (P=0.001) but LDL-c levels decreased significantly (P=0.002). Triglycerides and total cholesterol levels did not change significantly after the intervention (P=0.27, P=0.38, respectively). Maximum oxygen consumption increased significantly in evening exercises (P= 0.013). Body fat percentage and body mass index decreased significantly in both the morning and evening (P= 0.001).

Conclusion: Our findings revealed that aerobic exercises in the morning and evening had similar influence on lipid profile while the increase in aerobic capacity in the evening was more than that in the morning.