Objective To investigate how the relationship of infant weight gain with adolescent body mass index (BMI) differs for individuals born during and before the obesity epidemic era.
Design Data from two British birth cohorts, the 1946 National Survey of Health and Development (NSHD, n=4199) and the 2001 Millennium Cohort Study (MCS, n=9417), were used to estimate and compare associations of infant weight gain between ages 0 and 3 years with adolescent outcomes.
Main outcome measures BMI Z-scores and overweight/obesity at ages 11 and 14 years.
Results Infant weight gain, in Z-scores, was positively associated with adolescent BMI Z-scores in both cohorts. Non-linearity in the MCS meant that associations were only stronger than in the NSHD when infant weight gain was above −1 Z-score. Using decomposition analysis, between-cohort differences in association accounted for 20%–30% of the differences (secular increases) in BMI Z-scores, although the underlying estimates were not precise with 95% CIs crossing 0. Conversely, between-cohort differences in the distribution of infant weight gain accounted for approximately 9% of the differences (secular increases) in BMI Z-scores, and the underlying estimates were precise with 95% CI not crossing 0. Relative to normal weight gain (change of −0.67 to +0.67 Z-scores between ages 0 and 3 years), very rapid infant weight gain (>1.34), but not rapid weight gain (+0.67 to +1.34), was associated with higher BMI Z-scores more strongly in the MCS (β=0.790; 95% CI 0.717 to 0.862 at age 11 years) than in the NSHD (0.573; 0.466 to 0.681) (p<0.001 for between-cohort difference). The relationship of slow infant weight gain (<−0.67) with lower adolescent BMI was also stronger in the MCS. Very rapid or slow infant weight gain was not, however, more strongly associated with increased risk of adolescent overweight/obesity or thinness, respectively, in the more recently born cohort.
Conclusions Greater infant weight gain, at the middle/upper end of the distribution, was more strongly associated with higher adolescent BMI among individuals born during (compared with before) the obesity epidemic. Combined with a secular change towards greater infant weight gain, these results suggest that there are likely to be associated negative consequences for population-level health and well-being in the future, unless effective interventions are developed and implemented.
- adolescent health
- general paediatrics
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Contributors WOJ conceptualised the study, carried out the analyses and drafted the initial manuscript. WOJ, DB and RH made substantial contributions to the interpretation of the data, revised the manuscript critically for important intellectual content, gave final approval of the version to be published and agree to be accountable for all aspects of the work.
Funding WOJ is supported by a UK Medical Research Council (MRC) New Investigator Research Grant (MR/P023347/1), and acknowledges support from the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre, which is a partnership between University Hospitals of Leicester NHS Trust, Loughborough University and the University of Leicester. DB is supported by the Economic and Social Research Council (grant numbers ES/M008584/1 and ES/M001660/1) and the Academy of Medical Sciences/the Wellcome Trust ’Springboard Health of the public in 2040' Award (HOP001\1025). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The UK MRC provides core funding for the MRC National Survey of Health and Development and for RH (MC_UU_12019/1, MC_UU_12019/2).
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement This research uses harmonised data from two cohort studies. The original and harmonised 1946 NSHD data (doi:10.5522/NSHD/Q101) are made available to researchers who submit data requests to firstname.lastname@example.org; see also the full policy documents at http://www.nshd.mrc.ac.uk/data.aspx. The original data for the 2001 MCS are available from the UK Data Archive (http://www.data-archive.ac.uk).