Plasma levels of interleukin-6 and C-reactive protein are associated with physical inactivity independent of obesity

It is recognized that the path from physical inactivity and obesity to lifestyle‐related diseases involves low‐grade inflammation, indicated by elevated plasma levels of inflammatory markers. Interestingly, contracting skeletal muscle is a major source of circulating interleukin‐6 (IL‐6) in response to acute exercise, but with a markedly lower response in trained subjects. As C‐reactive protein (CRP) is induced by IL‐6, we hypothesized that basal levels of IL‐6 and CRP reflect the degree of regular physical activity when compared with other markers of inflammation associated with lifestyle‐related morbidity. Fasting plasma/serum levels of IL‐6, IL‐18, CRP, tumur necrosis factor‐α (TNF‐α), soluble TNF receptor II (sTNF‐RII), and adiponectin were measured in healthy non‐diabetic men and women (n=84). The amount of leisure‐time physical activity (LTPA) was assessed by interview. Obesity was associated with elevated insulin, C‐peptide, triglycerides, low‐density lipoprotein, IL‐6, CRP, and adiponectin (all P