Here's how much exercise you need to see results

The benefits of regular exercise have been shown in study after study. It has been linked to lower risks of heart disease, depression, dementia, diabetes, and even some cancers.

So what's the shortest amount of time you can work out in order to start seeing some of these benefits?

A new paper, published in the Viewpoints section of JAMA, reviews the existing evidence on that question and concludes that this magic number is merely minutes.

In several studies the authors reviewed, 15 minutes of daily moderate activity was associated with a reduced risk of early death, and running for five to 10 minutes per day was associated with a reduction in the risk of early death and death due to heart disease in particular.

That's less than the weekly 2.5 hours of moderate intensity or 1.25 hours of vigorous intensity exercise that the US Centers for Disease Control and Prevention recommend - but still more than what most American adults actually do.

While doing more than the bare minimum of physical activity may lead to more noticeable results, the JAMA paper suggests that even a small, regular amount of exercise is enough to make a difference.

"For vigorous physical activity, low doses are related to large benefits," the authors write in the study. Setting aside those minutes is worth your while.

The authors, from the Radboud University Medical Center in the Netherlands and the Division of Cardiology at Hartford Hospital in Connecticut, also looked at the upper limit for when exercising more no longer shows significant health benefits.

They found that exercising moderately for more than 100 minutes per day didn't show any more reduced mortality rates, and neither did exercising vigorously for more than 12.5 hours per week.

This, of course, doesn't mean that more exercise is bad for you, the authors note, but merely that it isn't any better for you at those extreme limits. Only physical inactivity has shown negative health effects.

Overall, the paper is encouraging, suggesting that casual exercisers should keep it up while super-intense exercisers have no reason to gloat.

"Although lack of time is a critical barrier to engaging in physical activity," the researchers write, "these results suggest that even the busiest individuals should have time for this lowest effective dose of physical activity."