Gemini is a large population-based study of 2402 families with twins born in England and Wales between March and December 2007. Gemini families have been followed for over a decade, providing information about the twins’ growth, eating behaviours, appetite and the environment at home.

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Gemini aims to advance understanding of the genetic and environmental influences on obesity risk; to identify potentially modifiable determinants of excessive weight gain in early childhood; and to contribute to a longer-term programme of integrated genetic environmental research in preventive health behaviours.