Staying Active Lessens Age-Related Weight Gain, Especially in Women

December 15, 2010

December 14, 2010 (Chicago, Illinois) — Staying active in young adulthood appears to help individuals lessen the fattening effects of time, with results of a new study showing that physically active young adults do not put on as much weight as their less active counterparts [1]. While some weight gain appears inevitable--even the most active individuals had increases in weight and waist circumference over a 20-year period--maintaining high activity levels lessens the weight gain as people move into middle age, report investigators.

"Preventing weight gain can be something that is appropriate for people who are overweight, normal weight, or obese, so it crosses weight classes," lead investigator Dr Arlene Hankinson (Northwestern University, Chicago, IL) told heartwire . "And like many prevention strategies, it's usually easier to prevent something from happening than to treat it after you've already developed the problem."

The study is published in the December 15, 2010 issue of the Journal of the American Medical Association.

Analysis From the CARDIA Trial

To heartwire , Hankinson said there has been a lot of work looking at the association between physical activity and weight loss, with clinical trials testing different types of physical activity and their effects on helping obese individuals lose weight. Less is known, however, about what is required to prevent weight gain in the future.

Currently, public-health guidelines recommend regular physical exercise to prevent age-related weight gain. While this implies that higher physical-activity levels can prevent weight gain, said Hankinson, the data supporting the recommendation are based largely on cross-sectional observational and short-term clinical trials. Short-term studies, she noted, can't account for the changing risk of gaining weight with age. The purpose of this study was to evaluate the relationship between habitual physical-activity levels and changes in body-mass index (BMI) and waist circumference over a 20-year period.

In this analysis, the researchers analyzed data from the Coronary Artery Risk Development in Young Adults (CARDIA) trial, a prospective, longitudinal study with 20 years of follow-up. The group used an algorithm to compute a total activity score that factored in the intensity, frequency, and duration of the physical activity over the previous 12 months. As a reference, a score of 300 exercise units corresponded to at least 150 minutes of moderate to vigorous intensity exercise per week, the approximate amount recommended by the US Department of Health and Human Services (HHS).

Men and women who had high physical-activity levels in young adulthood (ages 18 to 30 years) gained less weight than individuals with low measures of physical activity. Based on BMI, men who maintained high physical-activity levels in young adulthood gained 2.6 kg less than their less active peers over the 20 years of the study, while women who were most active gained 6.1 fewer kg than those with low physical-activity scores.

Similarly, over the 20 years, the most active men and women gained 3.1 and 3.8 fewer cm in waist circumference than individuals with the lowest physical-activity scores in young adulthood.

Average Annual Changes in BMI And Waist Circumference in Men

Long-term physical-activity category BMI, mean changes/y (95% CI) BMI, mean change/y relative to lower activity level (95% CI) Waist circumference, mean changes/y (95% CI) Waist circumference, mean change/y relative to lower activity level (95% CI)
Lower 0.20 (0.17–0.23) 1.0 (reference) 0.67 (0.60–0.75) 1.0 (reference)
Moderate 0.14 (0.09–0.19) -0.06 (-0.11 to 0.00) 0.50 (0.36–0.64) -0.17 (-0.33 to -0.02)
Higher 0.15 (0.11–0.18) -0.05 (-10 to -0.01) 0.52 (0.43–0.61) -0.15 (-0.27 to -0.03)

Average Annual Changes in BMI and Waist Circumference in Women

Long-term physical-activity category BMI, mean changes/y (95% CI) BMI, mean change/y relative to lower activity level (95% CI) Waist circumference, mean changes/y (95% CI) Waist circumference, mean change/y relative to lower activity level (95% CI)
Lower 0.30 (0.25–0.34) 1.0 (reference) 0.67 (0.60–0.75) 1.0 (reference)
Moderate 0.25 (0.15–0.34) -0.05 (-0.16 to 0.05) 0.59 (0.40–0.79) -0.08 (-0.29 to 0.13)
Higher 0.17 (0.12–0.21) -0.13 (-0.19 to -0.07) 0.49 (0.39–0.58) -0.19 (-0.31 to -0.06)

Overall, men and women who engaged in a high level of physical activity, exceeding the recommended HHS guidelines for duration, frequency, and intensity, gained approximately 9 kg, or roughly 20 lbs over 20 years. On the other hand, men who did not participate regularly in physical activity, those with a "low" physical-activity score, gained nearly 13 kg (28 lbs), while women with a low score gained 15 kg (33 lbs) over 20 years.

"It's very possible that there are physiologic differences between men and women--the chief among them being pregnancy and menopause--that might account for the differences in weight gain, but there could be other reasons," said Hankinson. "However, I think there are different ways that women behave compared with men, and we are not able to capture all of those behaviors and account for them in a way that explains the gender differences."

The overall data showing weight gain in even the most active adults support previous studies suggesting that individuals might need to exercise more as they age to prevent incremental gains in weight over time, Hankinson told heartwire .

Of the 1338 individuals included in the analysis, more than one-third met the daily physical-activity requirements outlined by the HHS. These individuals experienced smaller annual increases in mean BMI and waist circumference than those who did not meet the recommended activity levels. Overall, men and women who exercised for more than 150 minutes per week at moderate to vigorous intensity gained 1.8 and 4.7 fewer kgs, respectively, that those who did not meet the HHS physical-activity requirements.

"The federal guidelines are a great starting point," said Hankinson. "We used it as an alternative definition to high activity in our study, and we found really similar results. The benefit of those guidelines is to prevent weight gain, and not just weight loss for cardiovascular benefit."

There are no conflicts of interest to report. The study is funded by grants from the National Heart, Lung, and Blood Institute.

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