Association between change in body composition and change in inflammatory markers: an 11-year follow-up in the Whitehall II Study.

CONTEXT Obesity is associated with low-grade inflammation, but the long-term effects of weight change on inflammation are unknown. OBJECTIVE The aim was to examine the association of change in weight, body mass index (BMI), and waist circumference with change in C-reactive protein (CRP) and IL-6 and to assess whether this association is modified by baseline obesity status. DESIGN AND SETTING The design was a prospective cohort study among civil servants (the Whitehall II Study, UK). We used data from two clinical screenings carried out in 1991-1993 and 2002-2004 (mean follow-up, 11.3 yr). PARTICIPANTS We studied 2496 men and 1026 women [mean age, 49.4 (sd=6.0) yr at baseline] with measurements on inflammatory markers and anthropometry at both baseline and follow-up. MAIN OUTCOME MEASURES We measured change in serum CRP and IL-6 during follow-up. RESULTS The mean increases in CRP and IL-6 were 0.08 [95% confidence interval (CI), 0.07-0.09] mg/liter and 0.04 (95% CI, 0.03-0.05) pg/ml per 1-kg increase in body weight during follow-up. Study members with a BMI less than 25 kg/m2 at baseline had an average increase in CRP of 0.06 (95% CI, 0.05-0.08) mg/liter per 1-kg increase in body weight, whereas the increase in those who were overweight (25≤BMI<30 kg/m2) and obese (BMI≥30 kg/m2) was greater: 0.08 (95% CI, 0.06-0.09) mg/liter and 0.11 (95% CI, 0.07-0.14) mg/liter, respectively (P value for interaction=0.002). Similar patterns were observed for changes in BMI and waist circumference. CONCLUSIONS Those who were overweight or obese at baseline had a greater absolute increase in CRP per unit increase in weight, BMI, and waist circumference than people who were normal weight.