Change in height, weight and body mass index: Longitudinal data from the HUNT Study in Norway

Objective: The aim of this study was to analyse changes in body weight and height, and the changes in the prevalence of overweight and obesity. Design: Prospective population based study with 11-year follow-up. Subjects: Norwegian men (n = 21565) and women (n = 24337) aged 20 years or more who participated in two health surveys, the first in 1984-1986 and the other in 1995-1997. Measurements: Height and weight were measured by using standardised procedures at both surveys, and we computed body mass index (BMI) as weight in kilo divided by the squared value of height in meters. Results: Participants who were younger than 50 years at the first survey showed a large increase in body weight, and men and women aged 20-29 years increased their weight with an average of 7.9 kg and 7.3 kg, respectively. Contradictory, participants who were 70 years or older had on average a weight loss. The prevalence of overweight (BMI 25.0-29.9 kg/m(2)) and obesity (BMI >= 30 kg/m(2)) increased between the surveys, especially in the youngest age groups. Overall, the proportion classified as obese increased from 6.7 to 15.5% among men and from 11.0 to 21.0% among women. Some of this increase was due to a reduction in height, which was most pronounced in the oldest age groups. Conclusion: During approximately 10 years, body weight increased in all age groups below 70 years, and the prevalence of overweight and obese persons was approximately 20% higher at the second survey compared with the first survey.