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Prospective associations between objective measures of physical activity and fat mass in 12-14 year old children: the Avon Longitudinal Study of Parents and Children (ALSPAC)

BMJ 2009; 339 doi: (Published 26 November 2009) Cite this as: BMJ 2009;339:b4544
  1. Chris J Riddoch, professor of sport and exercise science1,
  2. Sam D Leary, lecturer in statistics23,
  3. Andy R Ness, professor of epidemiology and codirector of the Avon longitudinal study of parents and children23,
  4. Steven N Blair, professor of epidemiology4,
  5. Kevin Deere, research assistant3,
  6. Calum Mattocks, research fellow1,
  7. Alex Griffiths, research assistant in statistics2,
  8. George Davey Smith, professor of clinical epidemiology5,
  9. Kate Tilling, senior lecturer in medical statistics3
  1. 1School for Health, Norwood House, University of Bath, Bath BA2 7AY
  2. 2Department of Oral and Dental Science, University of Bristol, Bristol
  3. 3Department of Social Medicine, University of Bristol
  4. 4Departments of Exercise Science and Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, USA
  5. 5MRC Centre for Causal Analysis in Translational Epidemiology, Department of Social Medicine, University of Bristol
  1. Correspondence to: C J Riddoch C.J.Riddoch{at}
  • Accepted 28 July 2009


Objective To investigate associations between physical activity at age 12 and subsequent adiposity at age 14.

Design Prospective birth cohort study with data collected between 2003 and 2007.

Setting Original recruitment in 1991-2 of 14 541 pregnant women living in the former County of Avon (United Kingdom).

Participants At age 12, 11 952 children were invited to attend the research clinic. Of these, 7159 attended, and 4150 (1964 boys, 2186 girls) provided sufficient data on exposure, outcome, and confounding variables.

Main outcome measure Fat mass at age 14, measured by dual emission x ray absorptiometry, associated with physical activity at age 12, measured by accelerometry.

Results Prospective associations of fat mass at age 14 (outcome) with physical activity at age 12 (exposure) were strong for both total activity (accelerometer counts/min) and for daily amount of moderate-vigorous physical activity (min/day). An extra 15 minutes of moderate-vigorous physical activity per day at age 12 was associated with lower fat mass at age 14 in boys (by 11.9% (95% confidence interval 9.5% to 14.3%)) and girls (by 9.8% (6.7% to 12.8%)). The proportion of physical activity due to moderate-vigorous physical activity was between 20% and 30% in boys and girls at the two ages.

Conclusions Higher levels of physical activity, in particular activity of moderate to higher intensities, are prospectively associated with lower levels of fat mass in early adolescence. Interventions to raise levels of physical activity in children are likely to be important in the fight against obesity.


  • We thank all the families who took part in this study, the midwives who helped in recruiting them, and the whole ALSPAC team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists, and nurses. We also thank Chris Bain for his insightful comments on an earlier draft of this paper.

  • Contributors: CJR was principal investigator, led the team that obtained funding from the National Heart, Lung and Blood Institute, wrote all drafts of the paper, and is guarantor for the study. SDL performed statistical analyses and helped write all drafts of the paper. ARN was deputy director of ALSPAC and led the team that obtained funding from the Wellcome Trust. SNB advised at all stages of the study. KD organised day to day aspects of data collection and liaison with parents and children. CM led the fieldwork team and participated in the statistical analysis. AG performed statistical analyses and helped write all drafts of the paper. GDS was director of ALSPAC and advised at all stages of the study. KT performed analyses and helped write all drafts of the paper. All authors contributed to all drafts of the paper and approved the final version.

  • Funding: ALSPAC is supported by the Medical Research Council, Wellcome Trust, UK Department of Health, Department of the Environment, Department of Education and the Environment, National Institutes of Health, and a variety of medical research charities and commercial companies. This research was specifically funded by grants from the US National Heart, Lung and Blood Institute (R01HL071248-01A1) and the Wellcome Trust (GR068049MA).

  • All researchers are independent of the main funding body. The funding sources had no input to the study design, apart from changes required by external peer reviewers.

  • Competing interests: None declared.

  • Ethical approval: Ethical approval for the study was obtained from the ALSPAC Law and Ethics Committee (approved as an institutional review board) and local research ethics committees.

  • Data sharing: ALSPAC is run as a supported access resource. Full details of the collaboration policy can be found at

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