People who maintain high activity levels throughout young adulthood gain significantly less excess weight in middle age than those who do not, research published in the Dec. 15 issue of the Journal of the American Medical Association indicates.

Men who reported high activity levels (one hour per day) gained 5.7 fewer pounds and women (more than 30 minutes per day) gained 13.4 fewer pounds than those with low activity levels, according to findings from a prospective longitudinal study that followed 3,554 men and women for 20 years.

Although the U.S. Department of Health and Human Services recommends at least 30 minutes of moderate-intensity activity, five days a week, few long-term data corroborated the amount of activity necessary to keep weight off until now.

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“Our results reinforce the role of physical activity in minimizing weight gain and highlight the value of incorporating and maintaining at least 30 minutes of activity into daily life throughout young adulthood,” the researchers wrote.

Arlene L. Hankinson, MD, of Feinberg School of Medicine at Northwestern University and colleagues measured physical activity and changes in BMI and waist circumference among men and woman who participated in the Coronary Artery Risk Development in Young Adults (CARDIA) study.

The researchers surveyed study participants to determine how often they engaged in 13 moderate- to vigorous- intensity activities using the CARDIA Physical Activity History questionnaire at six different study time points. Participants who stayed within the same physical activity category for at least two-thirds of the follow-up period were considered habitual exercisers.

Study findings revealed that 36.7% of participants maintained the government recommended 30-minute per day exercising equivalent. Although the effect of moderate exercise was more modest than the changes observed in high activity participants, these individuals still gained less weight and fewer inches. Differences between moderate exercisers and those with low activity levels were as follows:

  • 4 pounds (1.8 kg) total over 20 years for men and 0.03 kg/m2 per year
  • 10.4 pounds (4.7 kg) total over 20 years for women and 0.09 kg/m2 per year
  • 0.31 inches (0.08 cm) of waist circumference per year for men and 0.67 inches (0.17 cm) for women.

Participants who achieved moderate or inconsistent physical activity did not differ from low activity participants in weight gain during the 20-year period, the researchers noted, and added that exercise alone might still not prevent age-related weight gain.

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 wrote.