[The development of BMI in 4-year-olds in Tromsø 1980 to 2005].

BACKGROUND: Studies indicate that the number of overweight adults and children in Norway is increasing. The aim of this study was to find out whether the epidemic of obesity has reached 4-year olds in Tromsø.

MATERIAL AND METHOD: The study is retrospective and compares cross-sectional surveys to find trends. Age in months, height and weight of 4-year olds were collected from child health care centre records in Tromsø, Norway. Data from 1645 children born in 1976, 1981, 1986, 1991 and 2001 were collected. The body mass index (BMI) was calculated and adjusted for age with standard deviation scores. The children were classified as normal or overweight based on the recommendations from the International Obesity Task Force.

RESULTS: Mean BMI was 15.9 kg/m2 for boys and 15.8 kg/m2 for girls born in 2001. BMI had not changed significantly from that for children born in 1976. The prevalence of overweight in girls has increased significantly from 7.2 % to 16.8 % in the same period (p = 0.02). The prevalence of overweight in boys born in 2001 was 8.8 %; this is not significantly different from those born in 1976. At the two most recent measurements the prevalence of overweight in girls was significantly higher than the prevalence of overweight in boys.

INTERPRETATION: The increasing prevalence of overweight in girls may indicate that the epidemic of obesity is starting to affect 4-year-old girls in Tromsø. The development is worrying and should be further monitored and followed up.