couple walking on beachTwo new, large scale studies are helping to clarify the effects of exercise on longevity and also how much exercise is the right amount.  The conclusion? Doing a few hours of exercise every week will probably help you live longer, but doing a whole lot more exercise doesn’t provide much extra benefit.

New Exercise Research Studies

In the broader of the two studies, researchers with the National Cancer Institute, Harvard University and other institutions gathered and pooled data about people’s exercise habits from six large, ongoing health surveys, comprising information on more than 661,000 adults, most of them middle-aged. Using this data, the researchers stratified the adults by their weekly exercise time, from those who did not exercise at all to those who worked out for 10 times the current recommendations or more (meaning that they exercised moderately for 25 hours per week or more). Then they compared 14 years’ worth of death records for the group.

The study found, unsurprisingly, that the people who did not exercise at all were at the highest risk of early death. But those who exercised a little, not meeting the recommendations but doing something, lowered their risk of premature death by 20 percent. Those who met the guidelines precisely, completing 150 minutes per week of moderate exercise, enjoyed greater longevity benefits and 31 percent less risk of dying during the 14-year period compared with those who never exercised. The sweet spot for exercise benefits, however, came among those who tripled the recommended level of exercise, working out moderately, mostly by walking, for 450 minutes per week, or a little more than an hour per day. Those people were 39 percent less likely to die prematurely than people who never exercised.

At that point, the benefits plateaued, the researchers found, but they never significantly declined. Those few individuals engaging in 10 times or more the recommended exercise dose gained about the same reduction in mortality risk as people who simply met the guidelines. They did not gain significantly more health advantage for the additional hours spent exercising. But they also did not increase their risk of dying prematurely.

The other new study of exercise and mortality reached a somewhat similar conclusion about intensity. While a few recent studies have intimated that frequent, strenuous exercise might contribute to early mortality, the new study found the reverse. For this study, Australian researchers closely examined health survey data for more than 200,000 Australian adults, determining how much time each person spent exercising and how much of that exercise qualified as vigorous, such as running instead of walking, or playing competitive singles tennis versus a sociable doubles game. Then, as with the other study, they checked death statistics.

Then, as with the other study, they checked death statistics. And as in the other study, they found that meeting the exercise guidelines substantially reduced the risk of early death, even if someone’s exercise was moderate, such as walking. But if someone engaged in even occasional vigorous exercise, he or she gained a small but not unimportant additional reduction in mortality. Those who spent up to 30 percent of their weekly exercise time in vigorous activities were 9 percent less likely to die prematurely than people who exercised for the same amount of time but always moderately, while those who spent more than 30 percent of their exercise time in strenuous activities gained an extra 13 percent reduction in early mortality.

Exercise_Graphic_yrs-gained

Researchers from Brigham and Women’s Hospital (BWH) have quantified how many years of life are gained, by being physically active at different levels, among all individuals as well as among various groups with different body mass index (BMI). Courtesy of BWH

The Long Term Benefit

So how much could you extend your life?  To sum it up, 75 minutes of brisk walking per week equates to an extra 1.8 years of life expectancy as opposed to staying sedentary. Increase that to 150–299 minutes of brisk walking per week and the gain in life expectancy goes up to 3.4 years. Make it 450 minutes per week and the estimated life expectancy jumps by 4.5 years.

The research also found that people whose weight is above the recommended level still benefit from physical activity. The studies indicated that the best results were obtained by those with normal weight who exercise. These people added 7.2 years to their life expectancy compared to people with a BMI (body mass index) of 35 or more (normal BMI ranges between 18.5 and 24.9) who undertook no exercise in their free time.

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