Testing a model of physical activity and obesity tracking from youth to adulthood: the cardiovascular risk in young Finns study.

Objective: To test a potential model of the relationship between physical activity and obesity from youth to adulthood.

Design: Longitudinal study data from the cardiovascular risk in young Finns study.

Subjects: A total of 1319 boys (n=626) and girls (n=693) aged 9, 12, 15 and 18 years were randomly selected from five university towns and their rural surroundings in 1980. They were followed up for 21 years. In 2001 they were 30, 33, 36 and 39 years old.

Measurements: Physical activity was assessed by a short questionnaire at two measurement points. Obesity was measured by body mass index (BMI) and sum of skinfolds in 1980 and BMI and waist circumference in 2001.

Results: Structural equation analysis (LISREL) indicated that the prevalence of abdominal obesity in adulthood was directly affected by adult physical activity (beta (beta)=-0.16, t=-4.02, P< 0.05 for men, beta=-0.12, t=-3.35, P<0.05 for women) and indirectly via youth physical activity (beta=-0.10, t=-4.68, P< 0.05 for men, beta=-0.07, t=-4.54, P<0.05 for women). Obesity tracked significantly from youth to adulthood (beta=0.41, t=11.13, P<0.05 for men, beta=0.34, t=9.39, P<0.05 for women). Youth physical activity might reduce body weight in youth but was not directly associated with adult abdominal obesity in either men or women. The model accounted 19% of abdominal obesity in men and 13% in women. The path from youth physical activity to adult obesity through youth obesity seemed to be stronger than the path through adult physical activity.

Conclusions: This study lends general support to the hypothesized model that abdominal obesity in adulthood is directly related to adult physical activity and youth overall obesity in both sexes. Youth physical activity had an indirect effect on abdominal obesity through the maintenance of physical activity in adulthood. Participation in and maintaining physical activity from youth to adulthood may have an important role in reducing obesity in adulthood.