BMJ  2005;331:453-454 (20 August), doi:10.1136/bmj.331.7514.453-b

Letter

Early life risk factors for obesity in childhood

Early feeding is crucial target for preventing obesity in children

EDITOR—Reilly et al present their findings on some early life risk factors for obesity at age 7 in a cohort of 7758 children born in the early 1990s.¹ We believe that their conclusions about breast feeding and time of weaning are flawed.

The investigators infer that these early feeding factors are unimportant because they are not independently associated with the obesity outcome in a statistical model that includes more proximal, parental, and prenatal factors. If early feeding factors exert their influence on childhood obesity largely through a causal pathway that includes other factors in the investigators' statistical models then it is not surprising that the early feeding factors do not emerge as independent predictors: it is a mistake to infer that these factors are therefore unimportant. The central public health issue is to identify the modifiable risk factors that can reasonably be assumed to be causal for obesity in children.

We believe that there is sufficient bio-behavioural and epidemiological evidence to support the idea that infant feeding practice directly affects early weight gain, and that trials of early feeding interventions to prevent later obesity in children are justified.^2-5 The investigators' univariate findings that early feeding factors predict later obesity add to this evidence, and their multivariate results should not be used to weaken the evidence on grounds of specious confounding. These data could be reanalysed with more attention paid to plausibly causal pathways.

buchan{at}manchester.ac.uk
Medical School, University of Manchester, Manchester M13 9PT

Medical School, University of Manchester, Manchester M13 9PT

Department of Primary Care, University of Liverpool, Liverpool L69 3GB

Institute of Child Health, University College London, London WC1N 1EH

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Competing interests: None declared.

References

1. Reilly JJ, Armstrong J, Dorosty AR, Emmett PM, Ness A, Rogers I, et al. Early life risk factors for obesity in childhood: cohort study. BMJ 2005;330: 1357. (11 June.)[Abstract/Free Full Text]
2. Stettler N, Stallings VA, Troxel AB, Zhao J, Schinnar R, Nelson SE, et al. Weight gain in the first week of life and overweight in adulthood: a cohort study of European American subjects fed infant formula. Circulation 2005;111: 1897-903.[Abstract/Free Full Text]
3. Owen CG, Martin RM, Whincup PH, Smith GD, Cook DG. Effect of infant feeding on the risk of obesity across the life course: a quantitative review of published evidence. Pediatrics 2005;115: 1367-77.[Abstract/Free Full Text]
4. Baker JL, Michaelsen KF, Rasmussen KM, Sorensen TI. Maternal prepregnant body mass index, duration of breastfeeding, and timing of complementary food introduction are associated with infant weight gain. Am J Clin Nutr 2004;80: 1579-88.[Abstract/Free Full Text]
5. Blyth R, Creedy DK, Dennis CL, Moyle W, Pratt J, De Vries SM. Effect of maternal confidence on breastfeeding duration: an application of breastfeeding self-efficacy theory. Birth 2002;29: 278-84.[CrossRef][ISI][Medline]

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Relevant Article

Early life risk factors for obesity in childhood: cohort study

John J Reilly, Julie Armstrong, Ahmad R Dorosty, Pauline M Emmett, A Ness, I Rogers, Colin Steer, Andrea Sherriff for the Avon Longitudinal Study of Parents and Children Study Team
BMJ 2005 330: 1357. [Abstract] [Full Text] [PDF]