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.

Change in body mass index and its impact on blood pressure: a prospective population study.

BACKGROUND: Overweight and obesity increase the risk of elevated blood pressure, but the knowledge of the effect of weight change on blood pressure is sparse. OBJECTIVE: To investigate the association between change in body mass index (BMI) and change in diastolic blood pressure (DBP), systolic blood pressure (SBP), and hypertension status. DESIGN: Two population-based cross-sectional studies, one in 1984-86 and the other in 1995-97. SETTING: The Nord-Trondelag Health Study (HUNT). PARTICIPANTS: We included 15,971 women and 13,846 men who were 20 y or older at the first survey, without blood pressure medication at both surveys and without diabetes, cardiovascular disease or dysfunction in daily life at baseline. MEASUREMENTS: Weight, height and blood pressure were measured standardised. Change in BMI was categorised as stable (initial BMI+/-0.1 kg/m2 each follow-up year), increased or decreased, and BMI was categorised by using World Health Organisation's categorisation (underweight BMI: <18.5 kg/m2, normal weight BMI: 18.5-24.9 kg/m2, overweight BMI: 25.0-29.9 kg/m2, obesity BMI> or =30 kg/m2). RESULTS: An increase in BMI and a decrease in BMI were significantly associated with increased and decreased SBP and DBP, respectively, compared to a stable BMI in both genders and all age groups, although the strongest effect was found among those who were 50 y and older. The adjusted odds ratio for having hypertension at HUNT 2 was 1.8 (95% confidence interval (CI): 1.5, 2.2) among women and 1.6 (95% CI: 1.4,1.8) among men aged 20-49 y who increased their BMI compared to those who had stable BMI. A similar, but weaker association was found among women and men aged 50 y or more. The mean change in both SBP and DBP was higher for those who changed BMI category from first to the second survey than for those who were in the same BMI class at both surveys. CONCLUSIONS: Our result supports an independent effect of change in BMI on change in SBP and DBP in both women and men, and that people who increase their BMI are at increased risk for hypertension.

Weight change and mortality: the Nord-Trøndelag Health Study.

OBJECTIVES: The prevalence of obesity is increasing. Overweight and obese people have increased mortality compared with normal weight people. We investigated the effect of weight change on mortality. DESIGN: Prospective population study. SETTING: We utilized data from two large population-based health studies conducted in 1984-86 and 1995-97 respectively. Cox proportional hazards models were used to calculate mortality rate ratios (RRs) with 95% confidence intervals (CIs) between people with a stable weight and people who lost or gained weight. Subjects. Totally 20,542 men and 23,712 women aged 20 years or more, without cardiovascular disease or diabetes at the first survey and without a history of cancer at the second survey were followed up on all-cause mortality for 5 years after the second survey. RESULTS: We found no association between weight gain and mortality. People who lost weight had a higher total mortality rate compared with those who were weight stable [RR was 1.6 (95% CI: 1.4-1.8) in men and 1.7 (95% CI: 1.5-2.0) in women]. Similar associations were found for cardiovascular and noncardiovascular mortality. Additional analysis showed a linear increase in mortality rates across categories of weight loss for both men and women (P < 0.001). There was a statistically significant interaction between weight change and initial BMI, but only amongst men (P = 0.001). CONCLUSIONS: Weight loss, but not weight gain, was associated with increased mortality amongst men and women. Although underlying undiagnosed disease is the most plausible explanation for this finding, the similar associations found for total mortality, cardiovascular mortality, and noncardiovascular mortality makes the causal pathway somewhat enigmatic.

BMI change and leisure time physical activity (LTPA): an 11-y follow-up study in apparently healthy men aged 20-69 y with normal weight at baseline.

OBJECTIVE: To study the association between self-reported leisure time physical activity (LTPA) at baseline and change in body mass index (BMI). DESIGN: Prospective observational study with a 11-y follow-up period. SETTING: A total population-based health survey in one county was performed in 1984-1986 (HUNT 1) and repeated in 1995-1997 (HUNT 2). PARTICIPANTS: In total, 21 685 men participated in both surveys. In the present study, we included only apparently healthy 20-69-y-old men participating in both surveys and who had a normal body weight (BMI 18.5-24.9 kg/m(2)) at baseline-leaving 8305 men for the analyses. In all, 6945 men answered all questions about LTPA and 6749 men had complete data in the multiple analyses. MEASUREMENTS AND MAIN RESULTS: At HUNT 1, the participants answered questions (self-reported) about the intensity, frequency and duration of LTPA. The association between change in BMI and LTPA was investigated in multiple linear regression analyses. Adjusted for smoking, education, age and BMI at baseline, the physical active cohort gained less weight than the inactive cohort. Low, moderate and high levels of LTPA showed a U-shaped effect adjusted for smoking, education, age and BMI at baseline. Adjusted for BMI and age at baseline, the high-intensity part of the physically active cohort gained less weight than the low-intensity group. CONCLUSION: This study has demonstrated a moderate BMI effect of LTPA at the population level; however, even a high level of LTPA did not prevent weight gain during the 11-y follow-up period.