To the Editor: Dr Hankinson and colleagues1 reported on the relationship of activity and body mass index (BMI) over 20 years in a large, ethnically diverse cohort of young to middle-aged adults participating in the CARDIA study. Weight gain is a major underlying risk factor for mortality secondary to the development of diabetes, heart disease, and cancer.2 In their analysis, being in the highest tertile of activity was associated with a reduction in the rate of increase in both BMI and waist circumference. However, individuals in this highest activity tertile still experienced significant increases in both BMI and waist circumference over time.
Jolley S, Porter B, Amory J. Physical Activity and Weight Gain Over 20 Years. JAMA. 2011;305(13):1297-1298. doi:10.1001/jama.2011.397