15 minutes daily exercise prolongs life 3 years - time to get off the couch?

What's the fittest city in America? And where will you find the nation's least-fit folks? To find out, the American College of Sports Medicine looked at smoking rates, eating and exercise habits, prevalence of obesity and other ailments, etc. in the nation's biggest metropolitan areas and gave each community an overall fitness score. Keep clicking to see the ranking's "bottom 20" - the least fit major cities in the country. Is your community on the list?
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(CBS/AP) Excuses for not exercising might be running out. A new study suggests 15 minutes a day is all it takes to reap big health benefits from breaking a sweat.

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Come on people - are you too busy to squeeze 15 minutes into your daily schedule?

This study "may convince many individuals that they are able to incorporate physical activity into their busy lives," Dr. Anil Nigam, chief of clinical care at the Montreal Hear Institute, said in an email. Nigam was not involved in the study but wrote an accompanying editorial published in the same August 15 issue of The Lancet where it was published.

Make no mistake, more exercise is better. Besides strengthening muscle, regular activity reduces disease risk and improves mental health. But not everyone has the time, so researchers set out to find the minimum amount of physical activity needed for health benefits.

As a benchmark, scientists from the National Health Research Institutes in Taiwan used the 30 minutes-per-day exercise recommendation from the World Health Organization's fitness guidelines. Nearly 416,000 Taiwanese adults were asked how often they had exercised in the previous month. Based on their answers, they were separated into five groups ranging from inactive to highly active. Researchers tracked their health for an average of eight years to project life expectancy.

The scientists said the adults who exercised just 15 minutes a day - or 90 minutes a week - extended their life expectancy by three years and cut their risk of death by 14 percent, compared to sedentary individuals. Both men and women benefited equally from the minimum activity. But why stop at the minimum? An additional 15 minutes of exercise reduced death risk by another 4 percent compared with the inactive group.

The study was observational though, meaning health benefits may not result entirely from exercise. Also, exercise frequency was self-reported by participants. But researchers said they took those factors into account along with others that might affect health like smoking and drinking.

For the sedentary, the message is simple, said I-Min Lee of the Harvard School of Public Health.

"Get off the couch and start moving."