The impact of intensified exercise training on insulin resistance and fitness in overweight and obese women with and without polycystic ovary syndrome

Objective To evaluate mechanisms of insulin resistance (IR) in overweight and obese women with and without polycystic ovary syndrome (PCOS) and explore relationships between IR, fitness and body mass index (BMI) at baseline and following exercise intervention. Design Prospective controlled intensified exercise intervention study. Patients A total of 20 overweight (BMI > 25 kg/m(2)) and obese (> 30 kg/m(2)), reproductive-aged PCOS women and 13 non-PCOS overweight, healthy controls of comparable BMI and age were studied at baseline. Measures were repeated in 13 PCOS and eight control women following three 1-h exercise sessions per week over 12 weeks. Measurements Insulin resistance was measured by glucose infusion rate on euglycaemic hyperinsulinaemic clamp, and fitness was assessed by VO2max. Results At baseline, PCOS women were 46% more insulin resistant than controls (175 6 vs 257 2 mg/m(2) /min, P < 0 05) with IR independently associated with VO2max and BMI in the PCOS group only (P < 0 01). Postexercise IR improved across both groups (P < 0 01). In PCOS women, IR improved by 16% (P < 0 05) but was not restored to the same level as controls (P < 0 05). Improvement in IR and in VO2max was related to the PCOS group (r 2 = 0 85, P < 0 05), yet change in IR and in fitness was not related. No associations were found in controls. Conclusions While intensified exercise improves IR in PCOS women, a higher IR persisted following exercise in PCOS women, and a clear relationship between improved IR and improved fitness was not found. Therefore, other mechanisms of, and therapies for, IR must be explored in PCOS as IR remains higher than observed in non-PCOS controls.