The role of IL-6 in exercise-induced anorexia in normal-weight boys

Our previous study showed that interleukin-6 (IL-6) is associated with suppression of appetite after high-intensity exercise (HIEX), but an independent role in food intake (FI) was not defined. We hypothesized that IL-6 suppresses appetite and FI, independently of appetite hormones, after HIEX in normal-weight (NW) boys. We investigated the effect of HIEX, with and without the inflammation inhibitor ibuprofen (IBU), on IL-6, other biomarkers of inflammation and appetite, FI, and ratings of appetite in NW boys. Fifteen NW boys (aged 13-18 years) were randomly assigned in a crossover design to 4 sessions: (i) water and rest, (ii) IBU and rest, (iii) water and HIEX, and (iv) IBU and HIEX. HIEX consisted of three 10-min bouts of exercise at 75% of maximal oxygen uptake with 90 s of active rest between bouts. IBU (300 mg) was given as a liquid suspension. FI, ratings of appetite, and plasma biomarkers of appetite, inflammation, stress, and glucose control were measured. FI was not affected by HIEX or IBU. Appetite increased over time (p = 0.002) but was lower after HIEX (p < 0.001) and not affected by IBU. HIEX, but not IBU, resulted in higher levels of IL-6 (p < 0.001) and cortisol (p < 0.001) and lower active ghrelin (p < 0.001). IL-6 correlated with active ghrelin (r = 0.37; p = 0.036) and cortisol (r = 0.26; p = 0.049). An independent role for IL-6 in appetite suppression was not supported. However, IL-6 was correlated with active ghrelin and cortisol, thus potentially mediating appetite via these interactions.