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Increased Physical Activity Spurs Prolonged Life by 69%

Expending energy by walking, climbing stairs, doing household chores, or even washing windows enhances survival in older adults. Compared with individuals with the lowest activity level, those at the highest level had a 69% lower risk of all-cause death, Todd Manini, Ph.D., of the National Institute on Aging here, and colleagues, reported

The researchers studied the energy expenditure during free-living activity in 302 high-functioning, biracial, community-dwelling older adults (ages 70 to 82; 150 men, 152 women). Fifty-five participants (18.2%) died during follow-up.

An important strength of this study, Dr. Manini wrote, was the accurate and precise method of determining energy expenditure. Earlier studies have used questionnaire assessments, which were subject to recall bias, he said. In this study, the participants’ total energy expenditure over two weeks was assessed with an accurate and precise method using doubly labeled water (water labeled with the stable isotopes of 2H, eliminated as water, and 18O, eliminated as water and carbon dioxide).

Participants were divided into three energy tertiles (low, <521 kcal/d; middle, 521 to 770 kcal/d; and high, >770 kcal/d) and were followed for a mean of 6.15 years from 1998 to 2006.

As a continuing risk factor, a mean (SD) increase in free-living activity energy expenditure (287 kcal/d) was associated with a 32% lower risk of all-cause mortality after adjusting for age, sex, race, study site, weight, height, percentage of body fat, and sleep duration (hazard ratio, 0.68; 95% CI, 0.48-0.96).

The absolute risk of mortality was 12.1% in the highest tertile of energy expenditure, 17.6% in the middle, and 24.7% in the lowest tertile, the researchers reported.

Turning to well-established metabolic equivalent values for physical activity, the researchers said that for every 287 kcal/d in free-living energy expenditure there is an approximately 30% lower risk of mortality. Further estimation found that individuals who performed 75 minutes of activity a day would expend 287 kcal/d.

Activities that meet this metabolic equivalent include household chores (vacuuming, mopping the floor, washing windows, etc.), child/adult care, walking at a pace of 2.5 mph, and non-sitting work, or volunteering. Most important, they said, this accumulation is from usual daily activities that expend energy and not necessarily from volitional exercise.

Because the doubly labeled water method directly measures carbon dioxide production over an extended period, it is considered the most accurate estimate of free-living energy expenditure.

In conclusion, Dr. Manini noted that previous self-reported measurements may have underestimated the benefits of higher levels of physical activity in older adults. "Efforts to increase or maintain free-living activity energy expenditure will likely improve the health of older adults."

In an accompanying editorial, Steven Blair, P.E.D., of the Cooper Institute in Dallas, and William Haskell, Ph.D., of Stanford, wrote that a major contribution of this study is the use of a quantitative measurement of energy expenditure. "Higher levels of activity energy expenditure appear to be protective, and it is relevant to discuss how much and what type of physical activity is required to achieve these benefits," they wrote. "Ultimately public health experts should consider how these results can be translated into recommendations for individuals."

Practice Pearls:

· When talking with healthy older patients, suggest that physical activity, ranging from walking and climbing stairs to doing household chores or volunteer work, may keep them healthier and extend life.

· Note that in this study the researchers measured the actual energy expenditure of the subjects, rather than relying on self-reports of activity.

Journal of the American Medical Association, Todd M. Manini, et al, "Daily Activity Energy Expenditure and Mortality Among Older Adults," JAMA 2006; 296: 171-179.

Journal of the American Medical Association: Steven N. Blair and William L. Haskell, Editorial: "Objectively Measured Physical Activity and Mortality in Older Adults," JAMA 2006; 296: 216-218.


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