At All Ages, Exercisers Weigh Less

Most people get heavier as they age, but those who regularly do moderate to vigourous exercise have a lower body mass index and waist circumference than those who do less, according to the first in-depth study of how we age, exercise, and change weight through a lifetime.

Published in Medicine & Science in Sports & Exercise, the new research surveyed a racially and ethnically diverse group of 5,000 U.S. men and women. Their ages spanned from 20 to older than 70. The subjects were fitted with an accelerometre to measure their daily movements.

The key result: “With great consistency,” the researchers wrote, “higher levels of physical activity were associated with lower BMI and lower waist circumference.”

The average male weighed 184 in his 20s, 195 in his 30s, 202 in his 40s, 195 in his 50s, and 200 in his 60s. For women, the averages were 153 (20s), 167 (30s), 171 (40s), 170 (50s), and 168 (60s).

Physical activity decreased with each new 10-year age group. Among males, minutes of daily moderate to vigourous physical activity peaked at 41.4 minutes for those in their 20. After that, it dropped to 38.8 (30s), 35.8 (40s), 26.5 (50s), and 17.6 (60s). Women showed a similar trend, moving from 24.9 minutes in their 20s to 12 minutes in their 60s.

The researchers also looked at the quality of the study participants’ diets. Although those who scored high on diet quality tended to have lower BMI and waist circumference, the relationship proved only about half as strong as the connection between BMI/waist circumference and physical activity. Diet quality was highest in the oldest subjects (who were also the heaviest).

In an email to Runner’s World, lead author Russ Pate, Ph.D., said he “was struck by the dramatic trends across the age groups. With increasing age, physical activity declined dramatically, but diet quality tended to improve. This points strongly to the important impact of age-related decline in activity as an influence on weight status.”

This position is far from unanimously held by weight and exercise experts. The New York Times recently published an opinion piece by Indiana University School of Medicine professor Aaron E. Carroll, M.D., arguing that kilojoule reduction, not increased exercise, is the superior path to weight loss.

Pate disagrees. “Our paper shows clearly that in every age/gender group, leaner people are more physically active,” he notes. “This finding contributes to the growing body of evidence that reducing population levels of overweight and obesity will require increased physical activity.”

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