This study aimed to identify early life risk factors for obesity in children up to 3 years of age in the United Kingdom. The Avon Longitudinal Study of Parents and Children (ALSPAC) was used, with 8234 children aged 7 years and a subsample of 909 children with additional data on early growth-related risk factors. Obesity at age 7 was defined as a body mass index (BMI) ≥95th centile relative to UK reference data in 1990. Eight out of 25 putative risk factors were significantly associated with obesity: parental obesity, very early BMI or adiposity rebound, more than eight hours of television watching per week at age 3, catch-up growth, standard deviation score for weight at 8 and 18 months, weight gain in the first year, birth weight, and short sleep duration at age 3. The study highlights the importance of early life environmental factors in programming obesity risk and suggests these as potential targets for future prevention interventions.This study aimed to identify early life risk factors for obesity in children up to 3 years of age in the United Kingdom. The Avon Longitudinal Study of Parents and Children (ALSPAC) was used, with 8234 children aged 7 years and a subsample of 909 children with additional data on early growth-related risk factors. Obesity at age 7 was defined as a body mass index (BMI) ≥95th centile relative to UK reference data in 1990. Eight out of 25 putative risk factors were significantly associated with obesity: parental obesity, very early BMI or adiposity rebound, more than eight hours of television watching per week at age 3, catch-up growth, standard deviation score for weight at 8 and 18 months, weight gain in the first year, birth weight, and short sleep duration at age 3. The study highlights the importance of early life environmental factors in programming obesity risk and suggests these as potential targets for future prevention interventions.