Aim: Our objective was to investigate whether overweight at a very young age predicts overweight at 5 years and to identify risk factors for overweight/obesity at 5 years, thereby making it easier for Child Health Services to focus their prevention strategies on risk groups.

Methods: We analysed data from the ABIS study (All Babies In Southeast Sweden), a prospective cohort study. Parents answered questionnaires between childbirth (n = 16,058) and 5 years (n = 7356).

Results: High body mass index (BMI; >95th percentile) at 1 year (adjusted odds ratio [AOR]= 6.57; 95% CI = 4.63–9.33; p < 0.001) and age-adjusted BMI > 25 at 2.5 years (AOR = 14.24; 95% CI = 10.52–19.29; p < 0.001) were associated with increased risk of obesity (age-adjusted BMI > 30) at 5 years. Heredity for type 2 diabetes (p = 0.022), high parental BMI and the child's own BMI at birth and at 1 year predicted higher BMI of the child at 5 years (p < 0.001). High parental education was inversely associated with child overweight (p = 0.054 respective p < 0.005).

Conclusion: Obesity at age 1 and at 2.5 years predicts obesity at 5 years. Obese parents, especially in families with heredity for type 2 diabetes and low education, should be targeted in early obesity prevention strategies by the Child Health Service.