Improving fitness and reducing obesity in preschool children

BMJ 2011; 343 doi: https://doi.org/10.1136/bmj.d6538 (Published 02 November 2011) Cite this as: BMJ 2011;343:d6538
  1. Scott Duncan, associate director
  1. 1Centre for Physical Activity and Nutrition, Auckland University of Technology, Auckland, New Zealand
  1. scott.duncan{at}aut.ac.nz

Multidimensional interventions can be effective in migrant populations

We are now in the midst of a global obesity epidemic that extends into early childhood; the World Health Organization estimated in 2010 that more than 42 million children under the age of 5 were overweight.1 Excess fat gain during this crucial developmental period can lay the groundwork for adverse psychological, social, and health outcomes.2 During the preschool years children approach an “adiposity rebound”—a rise in body mass index that occurs between 3-7 years—the timing of which determines the probability of developing obesity later in life.3 Of particular concern is the comparatively high prevalence of overweight and obesity among children from migrant communities and socially disadvantaged backgrounds.4 5 Finding ways to reduce the burden of obesity in these high risk populations is a key priority in many counties. In the linked randomised trial (doi:10.1136/bmj.d6195), Puder and colleagues assess the effect of a multidimensional lifestyle intervention on aerobic fitness and adiposity in predominantly migrant preschool children.6

Poor aerobic fitness has been suggested as an important contributor to obesity in early childhood. Although several cross sectional and longitudinal studies have noted inverse associations between cardiorespiratory fitness and total adiposity in older children and adolescents,7 data about these associations in preschool children are scarce. Furthermore, randomised controlled trials from which a cause and effect association between fitness and obesity in this age group can be determined are lacking. An increase in fitness probably has a protective effect on obesity, but children with excess adiposity may also reduce their physical fitness through a mediating factor, such as a decrease in overall physical activity.

Puder and colleagues show positive effects of a multidimensional lifestyle intervention on aerobic fitness and adiposity in more than 600 predominantly migrant preschool children living in Switzerland.6 The study, which targeted teachers, children, and parents over one school year, focused on physical activity, nutrition, media use, and sleep duration.8 A key element of the intervention was the consideration of multiple environmental and individual influences within the social ecological model.9 Compared with the control group children receiving the intervention had a significant increase in aerobic fitness (11%) and significant decreases in per cent body fat (5%), sum of four skinfolds (10%), and waist circumference (2%).

These findings offer hope for future public health campaigns that aim to tackle lifestyle disease in young migrant populations. The size of the improvements seen here would have considerable implications not only for overweight and obesity, but also for the many metabolic and psychosocial risk factors related to poor aerobic fitness, including high cholesterol, hypertension, insulin resistance, depression, and anxiety.7

The study builds on recent research that targeted low socioeconomic preschool children, parents, and nursery school teachers in a comprehensive 12 month nutrition and physical activity intervention.10 The cluster randomised controlled trial, which investigated 725 children, showed a significant improvement in fitness (per cent improvement not stated) and a 32% reduction in the number of overweight children. A common thread between these two successful interventions is that the focus extended beyond the individual child to encompass multiple dimensions of the preschool and home environments. Another similarity is that both interventions were maintained for a full school year. Taken together, these studies indicate that a considerable investment of time and resources is needed to achieve meaningful health improvements in high risk preschool children. Whether or not such improvements are sustained into the school years remains to be seen.

Puder and colleagues’ study also provides insight into the cause and effect association between fitness and obesity in preschool children. Despite the significant increase in fitness, the authors found no changes in objectively measured physical activity. This indicates that the beneficial effect of fitness on adiposity was not mediated by an increase in overall physical activity, and it justifies a specific focus on aerobic capacity as an obesity prevention strategy. It is also a reminder that young children should be regularly supported to engage in vigorous activities in addition to light or moderate play.

The findings of Puder and colleagues’ study are promising, and there is ample scope for future research in this area. The number of interventions focusing on fitness or obesity (or both) in older children greatly exceeds that in preschool children,11 and it is difficult to generalise the results from successful school based interventions, given the marked differences in cognitive and physical development and environmental influences on behaviour between these age groups. Little is known about how aerobic fitness and reduced adiposity in early childhood are related to other health indicators during growth and maturation. In addition, the short term and long term cost effectiveness of preschool interventions is largely unexplored. Although it can be assumed that any sustainable improvements in fitness or obesity will yield health benefits as children progress into adulthood, the likelihood that individuals will maintain these changes and the public health savings associated with a reduction in disease risk requires further research.


Cite this as: BMJ 2011;343:d6538


  • Research, doi:10.1136/bmj.d6195
  • Competing interests: The author has completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declares: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Provenance and peer review: Commissioned; not externally peer reviewed.


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