Low-grade systemic inflammation is suggested to play a role in the development of several chronic diseases including cancer. Higher levels of physical activity and lower adiposity have been associated with reduced levels of markers of systemic inflammation, such as C-reactive protein (CRP); however, reductions in CRP have not been consistently observed in randomized controlled trials of exercise. Purpose: To examine the effect of a 12-month aerobic exercise intervention on CRP levels in men and women. Methods: One hundred two men and 100 women, sedentary and of ages 40 to 75 years, with mean body mass index (BMI) of 29.9 and 28.7 kg/m2, respectively, were randomly assigned to a 12-month moderate-to-vigorous aerobic exercise intervention (6 d/wk, 60 min/d, 60-85% maximum heart rate) or control group. Fasting blood samples were collected at baseline and at 12 months. CRP levels were measured by high-sensitivity latex-enhanced nephelometry. Results: At baseline, CRP was 1.16 and 2.11 mg/L for men and women, respectively, and CRP was correlated with percent body fat (r = 0.48, P ≤0.001), BMI (r = 0.37, P ≤ 0.001), and aerobic fitness (r = -0.49, P ≤ 0.001). No intervention effects were observed for CRP in men or women, or when stratified by baseline BMI (≤30 versus ≥30 kg/m2), baseline CRP (<3 versus ≥3 mg/L), or change in body weight, body composition, or aerobic fitness. Conclusion: A 12-month moderate-to-vigorous aerobic exercise intervention did not affect CRP levels in previously sedentary men or women with average-risk CRP values at baseline.
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