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

ABSTRACT            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 between-group 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.            Keywords: Growth hormone, Insulin, Insulin-like growth factor 1, Exercise.