Effect of Six Months of Aerobic Exercise on Serum Levels of Insulin, Growth Hormone and Insulin-Like Growth Hormone 1 in Sedentary Obese Women

Background and Objectives: Inactivity, obesity and hormone disorders can lead to various diseases in obese and non-athletic individuals. The objective of this study was to investigate effects of six months of aerobic exercise on serum levels of insulin, growth hormone (GH) and insulin-like growth hormone 1 (IGF-1) in sedentary obese women. Methods: In this quasi-experimental study, 15 inactive, obese (body mass index 30) women aged 37-47 years were selected from employees of the Ferdowsi University in Mashhad (Iran), via purposive and available sampling. The participants were randomly divided into an experimental group (n=10) and a control (n=5) group. The experimental group performed 60 minutes of aerobic exercise at 55-65% of heart rate reserve, three sessions a week, for six months. Serum GH, IGF-1 and insulin levels were measured in both groups before the first training session and after the last training session. The Shapiro–Wilk test and the Levene s test were used to assess normal distribution of data and homogeneity of variance, respectively. Independent and dependent t-tests were used to compare betweengroup and within-group differences at significance of 0.05. All statistical analyses were performed using the SPSS software (version 18). Results: Serum concentrations of IGF-1 and insulin reduced significantly following the six-month aerobic exercise program. In addition, the exercise training caused an insignificant increase in GH levels. Conclusion: Our proposed aerobic exercise protocol significantly reduces IGF-1 level, which is closely related to the incidence of atherosclerosis, breast cancer, and colon cancer. The significant decline in insulin secretion following the six-month aerobic exercise program may provide more amounts of nutrients for muscle glucose metabolism.