Tracking of obesity and physical activity from childhood to adulthood: the Physical Activity Longitudinal Study.

OBJECTIVE

Body mass index (BMI) has shown moderate to strong stability through childhood into adulthood, while physical activity (PA) tracks less well. Tracking studies have often had limited follow-up lengths. The aim was to investigate BMI and PA tracking over 22 years from youth to adulthood.

METHODS

Subjects included 374 participants aged 7 to 18 years in the 1981 Canada Fitness Survey, who were re-evaluated in 2002-04. The stability of BMI and leisure-time PA energy expenditure (AEE) was assessed by inter-age correlations, maintenance of extreme quintiles and BMI status, and the prediction of adult overweight from youth BMI.

RESULTS

BMI tracking was moderate to strong (r=0.42-0.65) in females, and moderate (r=0.29-0.53) in males. Approximately 38% and 42% of youth in the highest and lowest BMI quintiles, respectively, remained in these quintiles as adults. About 83% of overweight youth remained overweight as adults, while 85% of overweight adults were not overweight youth. Almost all healthy weight adults had been healthy weight youth. The odds of being overweight in adulthood was 6.2 times greater (95% CI: 2.2-17.2) in overweight compared with healthy weight youth. PA tracking over 22 years was low and non-significant, but moderate over the final 15 years. Only 16% and 18% of youth in the highest and lowest PA quintiles, respectively, remained in these quintiles as adults.

CONCLUSIONS

BMI, but not PA, tracked well over 22 years in this sample. The majority of overweight youth remained overweight as adults; however, the majority of overweight adults were not overweight youth.