Background Obesity among children has become a worldwide epidemic. It is a threat to health and quality of life and imposes an economic burden on society.

Objectives To evaluate trends in obesity and overweight in 6-year-old children during 6 years (2002–7). To correlate children’s body mass index (BMI) percentiles at age 6 years to their BMI percentiles at age 3 years and 10 years.

Methods Height and weight of children at the age of 6 years were measured. Some of the children were also measured at the age of 10 years. Growth measurements at the age of 3 years were collected from the medical records.

Results 974 children were measured at the age of 6 years (52% of the cohorts). The prevalence of obesity and overweight increased constantly from 25.3% in the year 2003 to 31.1% in 2007. Obesity (BMI ⩾95%) was recorded in 14.1% of the children. At the age of 10 years, 38.9% of the children had BMI ⩾85% and 20% had BMI ⩾95%. Eighty-five per cent of the overweight or obese children at the age of 6 years continued to have BMI ⩾85% at the age of 10 years. At the age of 3 years 16.5% of the toddlers had BMI ⩾85% (n  =  176). A BMI ⩾95% was recorded for 13.6% of them. Ninety-four per cent of the toddlers with BMI ⩾95% continued to have BMI ⩾95% at the age of 6 years.

Conclusion Overweight and obesity is highly prevalent from early age and continues for years. Early intervention should therefore start in the first years of life.