BMC Public Health 2008, 8:171 http://www.biomedcentral.com/1471-2458/8/171 Although some exposures will have preceded the outcome (e.g., birth weight, breastfeeding, preterm delivery), they were measured retrospectively. This might have intro- duced recall bias. Also, exposure information might gen- erally be distorted because it is based on self-reports. Social desirability may be an issue (for instance reported smoking during first three years of the children's life). However, to bias estimates in either direction, the accu- racy of reports would need to be differential, i.e. depend- ent on the weight status of the child. This seems unlikely, as weight for height was not the primary outcome meas- ure of the studies. Conclusion The study represents the largest study on predictive factors for overweight and obesity in German children so far. With regard to overweight and obesity, the study provides further evidence of protective associations of breastfeed- ing (more than three months) and of having a certain size of living space (> 75 m2). Additionally, evidence is seen of an inverse association with educational level while female sex, other than German nationality, smoking in the living place and increasing birth weight category have been shown to be risk factors. Together with the evidence in the published literature, this analysis forms a basis upon which preventive measures could be developed. A British longitudinal cohort study found little evidence of incident cases of overweight/obesity emerging over adolescence, supporting the notion that efforts need to target children at a young age [15]. Health promotion strategies, for instance, to promote breastfeeding should complement wider societal change, particular with regards to the most vulnerable groups, i.e. children of migrants and children from families with low parental education. Competing interests The authors declare that they have no competing interests. Authors' contributions CJA suggested the idea for the article and wrote the man- uscript, supervised by UK and JC. UK was principal inves- tigator of the studies in East and West Germany. HB and JR were principal investigators of the study in Augsburg, Southern Germany. AL assisted in writing and reviewing the manuscript. All authors approved the final version of the manuscript. Acknowledgements We are grateful to Kate Knotts who commented a draft version of the report leading to this paper. 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