Author	S.G. Schrempft
Author	J. Wardle
Author	C.H.M. van Jaarsveld
Author	A. Fisher
Abstract	Dramatic increases in the prevalence of overweight and obesity have prompted a focus on prevention. Weight is known to have a strong genetic basis, but the speed of change in rates of overweight and obesity against a relatively stable gene pool suggests that exposure to an 'obesogenic' environment is important. The home environment is thought to play a key role in early weight trajectories, providing an avenue for long-term obesity prevention. There is evidence for associations between various aspects of the home environment and energy-balance behaviours; however, evidence for associations with weight is limited, particularly in early childhood. Few studies have used comprehensive, psychometrically-tested measures of the home environment, and no studies have tested for gene-environment interaction in the home context. This thesis uses data from the Gemini twin cohort to further examine the role of the home environment. Study one describes the development of a comprehensive measure of the home environment in early childhood, including the quantification of the extent that the home is likely to be obesogenic. Study two explores the utility of a novel tool called SenseCam to examine and validate aspects of the home environment measure. Study three identifies a number of maternal characteristics associated with the obesogenic quality of the home environment. Study four shows associations between the obesogenic quality of the home environment and energy-balance behaviours; while study five finds no association with weight. Findings from study six highlight the role of gene-environment interaction, showing that the heritability of weight is higher among children living in home environments with greater obesogenic potential. Overall, the findings of this thesis further understanding on how the home environment contributes to the development of overweight and obesity. Implications, limitations, and avenues for future research are discussed.