Conscripts born in 1980 were only 0.2 cm higher but weighed on average 3.3 kg more than those born in 1967. This weight gain corresponds to an average increase of body mass index (BMI) of 0.92 kg/m2. A description of geographical differences in changes of BMI is given.
All men born in Norway 1967-80, with Norwegian citizenship and known county of residence at the age of 18 are included, a total of 399,512 men. BMI was calculated for each birth cohort on the basis of data from the medical examinations for military service obtained from the Central Service Administration.
Significant geographical differences in changes of BMI were found. Conscripts from Northern Norway had the largest increase of BMI, 2.0 kg/m2. The percentage of conscripts from Northern Norway with a BMI > or = 30 kg/m2 (obesity) increased from 1.5 for those born in 1967 to 6.5 for those born 13 years later. The smallest weight gain was observed among conscripts from the central counties of southeastern Norway; their average BMI increased only 0.5 kg/m2. The geographical differences became evident in the 1973-76 birth cohorts and are present also among the more recent birth cohorts.
To disclose the causes of these differences would be important in the prevention of overweight in young men.