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

Scand J Med Sci Sports. 2007 Oct;17(5):580-7. doi: 10.1111/j.1600-0838.2006.00602.x.


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-alpha (TNF-alpha), 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<0.05). Importantly, physical inactivity was associated with elevated C-peptide (P=0.036), IL-6 (P=0.014), and CRP (P=0.007) independent of obesity, age, gender, and smoking. Furthermore, the LTPA score was inversely associated with IL-6 (P=0.017) and CRP (P=0.005), but with neither of the other markers. The results indicate that low levels of IL-6 and CRP - not IL-18, TNF-alpha, sTNF-RII, or adiponectin - reflect regular physical activity.

Publication types

  • Comparative Study

MeSH terms

  • Adiponectin / blood
  • Biomarkers
  • Body Mass Index
  • C-Reactive Protein*
  • Cytokines / blood
  • Female
  • Health Status
  • Humans
  • Interleukin-6 / blood*
  • Interleukins / blood
  • Life Style
  • Male
  • Middle Aged
  • Motor Activity*
  • Muscle Contraction / physiology
  • Obesity*
  • Pilot Projects


  • Adiponectin
  • Biomarkers
  • Cytokines
  • Interleukin-6
  • Interleukins
  • C-Reactive Protein