Exercise and liver fat reduction in pre-diabetes: moving beyond weight loss

Our proposed research will use innovative and valid, non-invasive techniques, including proton magnetic resonance spectroscopy (MRS), to measure the effect of 8 weeks of: i) low-intensity/low energy expenditure aerobic exercise training (LO-LO); ii) low-intensity/high energy expenditure aerobic exercise (LO-HI) iii) high-intensity/low energy expenditure aerobic exercise training (HI-LO) iv) progressive resistance (PRT) and v) placebo control on liver fat content, abdominal triglyceride partitioning (subcutaneous and visceral fat), serum aminotransferases, blood lipids/hormones, insulin sensitivity and aerobic fitness (VO2max/peak) in overweight and obese individuals with pre-diabetes. Specifically, subjects allocated to LO-LO will receive a supervised progressive cycling exercise program involving 2 days of exercise per week with one additional session at home each week, 45 minutes per session at 50% of maximal aerobic power (VO2max) (135 min per week). Subjects allocated to LO-HI will undertake 3 days of supervised exercise per week with one additional session at home each week, 60 minutes per session at 50% of VO2max (240 min per week); those in HI-LO will receive 2 days of supervised exercise per week with one additional session at home each week, 45 minutes per session at 70% of VO2max (135 min per week). Subjects allocated to PRT will receive a supervised progressive resistance training program involving 3 days of exercise per week, 8-10 exercises per session, 1-3 sets per exercise at 60-80% of 1-repetition maximum (1-RM) with sessions lasting 45- 60 minutes including warm up and cool down on a cycle ergometer. For the LO-LO, the LO-HI and HI-LO groups all supervised exercise sessions will be performed on a stationary cycle ergometer and supervised on a one-on-one basis by an exercise physiologist. The additional home-based session will involve brisk walking at the prescribed intensity. The PRT sessions will also be supervised by an exercise physiologist on a one-on-one basis. All exercise interventions will be progressed. The LO-LO group will begin cycling for 30 minutes at 50% V02 peak and this will progress to 45 minutes by week 3 of the intervention. The HI-LO group will begin cycling at 50% intensity for 30 minutes and this will progress to 45 minutes at 70% V02 peak by week 3 of the intervention. The LO-HI group will begin cycling for 45 minutes at 50% intensity and this will progress to 60 minutes by week 3 of the intervention. Heart rates and ratings of perceived exertion will be continuously monitored and the power output (Watts) increased in accordance with training adaptations over the 8 weeks to keep the same relative exercise intensity. Supervised sessions will be logged by the exercise physiology with heart rates, ratings of perceived exertion and blood pressure recorded. Adherence to home based sessions will be monitored using a home log book and record heart rates and ratings of perceived exertion.