Objective: To examine risk factors for rapid weight gain between 3 and 5 years of age.
Design: Nationally representative prospective cohort study.
Participants: A total of 11 653 preschool children participating in the UK Millennium Cohort Study, with anthropometry at 3 and 5 years.
Measurements: Weight gain z-scores were calculated from 3 to 5 years. Children in the top quarter of this distribution were classified as gaining weight rapidly. A total of 26 biological and early life, social, psychological, behavioural and environmental risk factors were examined.
Results: Among the participants, 13% of normal weight, 63% of overweight and 88% of obese 5-year olds had experienced rapid weight gain since 3 years of age. Six biological and early life factors and two social factors were found to be significantly associated with this growth pattern. In a mutually adjusted model, children were more likely to gain weight rapidly if they had a higher body mass index at age 3 (adjusted odds ratio: 1.27, 95% confidence interval: 1.23-1.32), if they were of Bangladeshi (adjusted odds ratio: 1.88, 95% confidence interval: 1.27-2.79) or black (adjusted odds ratio: 1.47, 95% confidence interval: 1.07-2.02) ethnicity, if their mother was overweight (adjusted odds ratio: 1.32, 95% confidence interval: 1.15-1.51) or had been overweight before pregnancy (adjusted odds ratio: 1.56, 95% confidence interval: 1.36-1.79), if their father was overweight (adjusted odds ratio: 1.56, 95% confidence interval: 1.34-1.81) or if their mother smoked during pregnancy (adjusted odds ratio:1.23, 95% confidence interval: 1.09-1.38). Children were also more likely to gain weight rapidly if others smoked in the same room (adjusted odds ratio: 1.31, 95% confidence interval: 1.16-1.49) or if they were a lone child in the household (adjusted odds ratio: 1.14, 95% confidence interval: 1.01-1.30).
Conclusions: Factors operating during pregnancy and early life increase the risk of rapid weight gain in young children; thus, signalling the importance of obesity prevention programmes before and during pregnancy and for children at an early age. In particular, these programmes should address parental weight status and smoking habits, both modifiable risk factors.