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doi:10.1016/j.orcp.2010.09.171

nvited Speakers

esistance and vascular changes. Epigenetic mech-nisms underpin much of this biology and theseathways coexist within populations in transition.considerable portion of childhood adiposity can

e explained by epigenetic variation at birth. Sug-esting the importance of the prenatal environmento later obesogenic sensitivity. The mechanismsnderpinning the effects of maternal obesity, onffspring obesity may also involve epigenetic pro-esses. The rise in gestational diabetes is a furtherathway of growing importance particularly in Asia.

oi:10.1016/j.orcp.2010.09.169

vidence-based obesity prevention in children

ohn J. Reilly

Royal Hospital for Sick Children and University oflasgow, Scotland

Prevention of childhood obesity has proved muchore challenging than might have been expected,

nd the aetiology of childhood obesity is more com-lex than it might seem. In addition, in the UK thereas been a marked gulf between the research evi-ence on aetiology and prevention and the policyction on prevention. The presentation will start byonsidering the knowledge of UK policymakers onargets for childhood obesity prevention, and theendency of UK policy to be generally unresponsiveo research evidence, yet sometimes overly sensi-ive to findings of individual studies. It will considerbriefly-the most well established behavioural tar-

ets for obesity prevention interventions, recentystematic reviews, and the most promising schoolnd community based interventions aimed at child-ood obesity prevention. Finally, the presentationill consider some emerging evidence, and thehallenges this evidence might present for child-ood obesity prevention in future: the size of thenergy imbalance experienced by contemporaryhildren and adolescents and the consequences thisas for the magnitude of lifestyle changes requiredo prevent obesity; heterogeneity in the aetiologyf obesity; heterogeneity in the prevention of obe-ity (such as differences between groups definedy age, socio-economic status, initial weight sta-us, or ethnicity); the ‘natural history’ of excesseight gain as well as obesity in contemporary chil-ren and adolescents, using an example from theLSPAC cohort study in England; the importance ofvidence on incidence and persistence of obesity, in

ddition to the more commonly studied prevalence,sing an example from the ALSPAC cohort.

oi:10.1016/j.orcp.2010.09.170

S87

ow do we measure sedentary behaviours inoung people?

ohn J. Reilly

Royal Hospital for Sick Children and University oflasgow, Scotland

Sedentary behaviour is now well establisheds being important to current and future healthf children and adolescents, particularly in theetiology, prevention, and treatment of child anddolescent obesity. Sedentary behaviour can noonger be seen as simply a lack of physical activity.ne major challenge in measurement is the emerg-

ng complexity of the construct, and it is unlikelyhat any single measurement method will cap-ure all the aspects of sedentary behaviour whichre likely to be of interest. Sedentary behavioursay be defined as lack of trunk movement, or

s activities with low energy expenditure, andeasured using ‘traditional’ accelerometry cali-rated against direct observation and/or energyxpenditure. Alternatively, accelerometers withnclinometers might provide more accurate mea-urement of sedentary behaviour, and can providenformation on posture (e.g. sitting vs. standingime) and posture transitions (e.g. bouts of sittingime, breaks in sitting) which may also be valu-ble. Other aspects of sedentary behaviour maye important, such as fidgeting, and these maye measured adequately using existing technol-gy. Screen time is arguably the most importantimension of sedentary behaviour for child healthnd development, but quantitative measurements challenging. Further research will be requiredn order to identify the most important aspects ofedentary behaviour to measure, and the choice ofhich aspect to measure should depend on the par-

icular application. Quantitative measurement ofedentary behaviour requires objective measure-ent, but some aspects of sedentary behaviour

re more amenable to objective measurement thanthers. At the very least, researchers should belear about which aspects of sedentary behaviourhey are measuring and why, should describe theeasurement methods used clearly, should useethods validated and calibrated in the paediatric