Background:Breastfeeding duration has been associated with less low-grade inflammation in healthy adolescents, but there is scarce information regarding obese subjects. This study aimed to evaluate whether exclusive breastfeeding is related to serum concentrations of inflammatory markers in a population of Spanish adolescents.Method:A cross-sectional study was performed on 1,001 adolescents (13.2 ± 1.2 years) randomly recruited from schools in southeast Spain. Data on breastfeeding duration were collected via a parental questionnaire. Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were determined by enzyme-linked immunosorbent assay. C-reactive protein (CRP) was determined by solid-phase chemiluminescent immunometric assay.Results:Nonadjusted and adjusted multivariate correlation analyses confirmed a strong association ( p < .001, 95% confidence interval) between the three markers of inflammation and exclusive breastfeeding duration. No significant differences were observed for IL-6, TNF-α, and CRP serum concentrations among normal weight, overweight, and obese adolescents, except for IL-6 between normal weight and obese subjects. Likewise, no significant association was found between these markers of inflammation and body mass index (BMI) z-score.Conclusions:We found a possible association between inflammatory markers and exclusive breastfeeding duration in adolescents, regardless of their BMI. This finding suggests that increased body weight or obesity might not mediate the association between breastfeeding and inflammation. These results contribute to the understanding of the relationship between breastfeeding and inflammatory markers in adolescents.