Background: Several studies have suggested an association between the increasing prevalence of allergicdiseases and dietary factors.

Objective: To prospectively explore the association between changes in body mass index (BMI) andsymptoms of asthma, rhinitis, rhinoconjunctivitis, and atopic dermatitis to find out whether an increase inBMI increases the risk of developing atopic diseases in adolescence.

Methods: Comprehensive questionnaires and anthropometric measurements were applied in a randomsubsample of the International Study of Asthma and Allergies in Childhood phase II (1995e1996, 9 to 11years of age) in Germany. Of these participants, 1,794 could be followed up in 2002 to 2003 in the Study onOccupational Allergy Risks (16 to 18 years of age). The associations between changes of BMI from baseline tofollow-up and incident and persistent respiratory diseases and atopic dermatitis were assessed.

Results: In logistic regression analyses, weight change in either direction was not statistically significantlyassociated with the incidence or persistence of any of the diseases of interest except for rhinitis. An increasein BMI was linked to an increased risk of incident rhinitis (odds ratio 1.9, 95% confidence interval 1.2e2.9).

Conclusion: These results indicate a nonsignificant trend between increased body weight and risk of atopicdiseases. Aside from limitations owing to a small subgroup of obese participants and questionnaire-basedasthma diagnosis, reasons might be related to an interaction between BMI and hormonal influences, age,and duration and severity of overweight. The results underline that BMI does not necessarily play a decisiverole in the course of atopic diseases in all populations.