Obesity is a common health problem. Obesity can start early in life, and it is thought that genetic factors may be important in people who become obese at a young age. Little is known about these genetic factors in children compared to adults. An international effort co-ordinated by the Early Growth Genetics consortium (EGG) is currently underway which aims to test for genetic effects on different measures of overweight and obesity in childhood. This proposal plans to carry out analysis of different measures of overweight and obesity in children in the ALSPAC cohort, and plans to share summary results of this analysis with EGG.