AIM: Our aim is to demonstrate that a healthy diet might reduce the relation between adiposity and inflammation, whereas an unhealthy diet may increase the effect of adiposity on inflammatory biomarkers. METHODS: In 618 adolescents (13-17 years) of the European HELENA study, data were available on body composition, a set of inflammation markers, and food intake determined by a self-administered computerized 24-h recall. A 9-point Mediterranean diet score and an antioxidant-rich diet score were used as dietary parameters and tested as moderator. Total body fat was represented by the sum of six skinfold thicknesses and central adiposity by waist circumference. A set of inflammation-related biomarkers was used as outcome: a pro/anti-inflammatory interleukins ratio, TGFbeta-1, C-reactive protein, TNF-alpha, 3 cell adhesion molecules, and 3 types of immune cells; gamma-glutamyltransferase (GGT) and homocysteine were used as cardiovascular disease risk biomarkers, and alanine transaminase (ALT) as liver dysfunction biomarker. Multiple linear regression analyses tested moderation by diet in the adiposity-inflammation association and were adjusted for age, sex, country, puberty, socioeconomic status. RESULTS: Both the Mediterranean and antioxidant-rich diet, and overall and central adiposity, were important in the moderation. Diet was a significant protective moderator in the effect of adiposity on the pro/anti-inflammatory interleukins ratio, TGFbeta-1, GGT, and ALT. CONCLUSION: In conclusion, in some cases, a diet rich in antioxidants and essential nutrients may attenuate the concentration of inflammatory biomarkers caused by adiposity, whereas a poor diet appears to contribute to the onset of early oxidative stress signs.