Maintaining a high level of physical activity throughout young adulthood curbed both the weight gain and the expanding waistline characteristic of middle age, according to a report in JAMA.
That finding, from a longitudinal study that tracked men and women during the 20-year transition from young adulthood to middle age, “highlights the value of incorporating and maintaining at least 30 minutes of activity into daily life,” said Dr. Arlene L. Hankinson of the department of preventive medicine at Northwestern University, Chicago, and her associates (JAMA 2010;304:2603-10).
The investigators undertook their study because public health guidelines recommending regular exercise have been “largely based on cross-sectional observational and short-term clinical evidence that cannot account for the changing risk of weight gain with increasing age,” the study investigators noted.
Moreover, it had never been shown that federal guidelines advocating 30 minutes of moderate to vigorous daily activity are sufficient to prevent weight gain during the transition to middle age, “when the highest risk of weight gain occurs,” they said.
Dr. Hankinson and her colleagues examined the issue using data from CARDIA (Coronary Artery Risk Development in Young Adults), a multicenter, longitudinal, cohort study of the development of coronary risk factors in young adults.
They assessed data collected for 3,554 subjects who were 18-30 years of age at baseline in 1985-1986 regarding self-reported participation in 13 specific sports, exercise, home maintenance, and occupational activities.
At all activity levels, men and women alike showed gains in weight, body mass index, and waist circumference during the study's 20 years of follow-up.
“Some age-related weight gain may be unavoidable in our society, as it has been observed even among a population of vigorously active runners through middle age,” the researchers noted.
However, habitual daily vigorous physical activity was associated with smaller increases in mean weight, BMI, and waist circumference, compared with moderate, inconsistent, or low activity, the investigators added.
Men with high activity levels gained 2.6 fewer kilograms, and women with high activity levels gained 6.1 fewer kilograms per year than did men and women with low activity levels.
Similarly, men with high activity levels gained 3.1 fewer centimeters and women with high activity levels gained 3.8 fewer centimeters in waist circumference per year.
However, only a small proportion of the study subjects (11% of men and 12% of women) maintained that high level of vigorous activity over 20 years.
Approximately 37% of the study cohort participated in regular activity equivalent to the levels recommended by the U. S. Department of Health and Human Services.
At that level of activity, men gained 1.8 fewer kilograms and women gained 4.7 fewer kilograms during follow-up than did study subjects who had lower levels of activity.
The National Heart, Lung, and Blood Institute supported the study. No financial conflicts of interest were reported.