Reducing childhood obesity is a major global public health challenge. However, interventions designed at changing individual or family behaviours often do not show an impact. It is important therefore to better understand the causes of childhood obesity. Whilst there is some evidence that factors in pregnancy are associated with obesity, it is unclear whether these are causes. It is also unclear whether different factors affect obesity at different ages.

For example, there is evidence that children whose mothers had gestational diabetes may have a greater risk of childhood obesity. Studies in Europe and South Asia have also reported that this effect may not emerge until later on in childhood. There is also evidence that infants born preterm are about two-fold more likely to be obese later in life than those born at term. However few studies have examined the association between preterm birth and BMI in later childhood.

In terms of socioeconomic factors, lower family socioeconomic position (SEP) has been associated with higher BMI from as early as 9 months. However, there is inconsistent evidence on the extent as to whether which the effect of SEP increases, decreases or remains constant over time. There is also evidence that neighbourhood exposures in the post-natal period (such as exposure to green spaces and area-level deprivation) are also associated with childhood BMI; however to our knowledge the effect of these exposures before birth has not been investigated.

The LifeCycle project is an EU initiative to harmonise key data from a number of EU studies, including ALSPAC. To maintain participant anonymity, we will be using innovative software called DataSHIELD to analyse the data. DataSHIELD allows the remote analysis of summaries of this harmonised data, but prevents the access of individual data.

The LifeCycle project provides a unique opportunity to examine how early life factors might relate to childhood BMI. In this ‘proof of principle’ study we will use DataSHIELD to carry out remote analyses of LifeCycle cohorts, selecting variables that have evidence for some effect on childhood BMI (maternal and paternal education, area level deprivation, access to greenspace, gestational diabetes and gestational age at birth). We will conduct analysis on BMI at different points throughout childhood to explore how the effect of these factors emerges over childhood.