Impact of physical activity on insulin levels in breast cancer survivors

Abstract

555 Background: Accumulating data suggest that body weight and physical activity may affect breast cancer risk and outcomes. Biological mechanisms underlying these relationships are not clear. Studies have demonstrated that high levels of insulin, often seen in obese and sedentary individuals, are also associated with an increased risk of breast cancer recurrence and breast cancer-related death. We sought to analyze whether exercise lowers insulin levels in a population of breast cancer survivors. Methods: Inactive women with early stage breast cancer who had completed adjuvant treatment were randomized to a 16 week, mixed cardiovascular and strength training exercise intervention, or to a normal care control group. Target exercise goals included 2 supervised strength training sessions and 90 minutes of unsupervised cardiovascular exercise each week. Fasting insulin and glucose levels, as well as measurement of weight, body composition, and circumference at the waist and hip, were collected at baseline and after 16 weeks in both groups, and changes in these measures were assessed. Results: One hundred and one women were randomized. Comparison of changes in anthropometric measures are presented in Table 1 . Baseline insulin levels were similar in the 2 groups. After the 16-week exercise or control period, insulin levels decreased by 2.86 μIU/ml in the exercise group (p=0.03), and by 0.27 μIU/ml in the control group (p=0.65). A comparison of the change in insulin levels across time in the 2 groups approached statistical significance (p=0.07). There was also a trend toward improvements in insulin sensitivity in the exercise group (p=0.09), with no change seen in fasting glucose levels. Conclusions: Physical activity was associated with a decrease in insulin levels and in hip circumference in breast cancer survivors. The relationship between physical activity and breast cancer prognosis may be mediated, at least partially, through changes in insulin levels and/or changes in fat mass or deposition. [Table: see text] No significant financial relationships to disclose.