Cytokine responses to repeated, prolonged walking in lean versus overweight/obese individuals

Objectives. Obesity is characterized by a pro-inflammatory state, which plays a role in the pathogenesis of metabolic and cardiovascular disease. An exercise bout causes a transient increase in pro-inflammatory cytokines, whilst training has anti-inflammatory effects. No previous study examined whether the exercise-induced increase in pro-inflammatory cytokines is altered with repeated prolonged exercise bouts and whether this response differs between lean and overweight/obese individuals. Design. Lean (n = 25, BMI 22.9 ± 1.5 kg/m2) and age-/sex-matched overweight/obese (n = 25; BMI 27.9 ± 2.4 kg/m2) individuals performed walking exercise for 30, 40 or 50 km per day on four consecutive days (distances similar between groups). Methods. Circulating cytokines (IL-6, IL-10, TNF-α, IL-1β and IL-8) were examined at baseline and <30 min after the finish of each exercise day. Results. At baseline, no differences in circulating cytokines were present between groups. In response to prolonged exercise, all cytokines increased on day 1 (IL-1β: P = 0.02; other cytokines: P < 0.001). IL-6 remained significantly elevated during the 4 exercise days, when compared to baseline. IL-10, TNF-α, IL-1β and IL-8 returned to baseline values from exercise day 2 (IL-10, IL-1β, IL-8) or exercise day 3 (TNF-α) onward. No significant differences were found between groups for all cytokines, except IL-8 (Time*Group Interaction P = 0.02). Conclusions. These data suggest the presence of early adaptive mechanisms in response to repeated prolonged walking, demonstrated by attenuated exercise-induced elevations in cytokines on consecutive days that occur similar in lean and overweight/obese individuals.