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How much exercise you need to keep your New Year's resolutions

NEW YORK -- A recent survey finds about 41 percent of Americans are making a New Year's resolution to live a healthier lifestyle. Another 40 percent say their goal for 2016 is to lose weight.

What will it take to live up to those personal promises?

David Marcus ran three marathons, but that was more than a decade ago. Since then he's had trouble fitting fitness into his busy life.

"I have a demanding job, family" Marcus told CBS News. "By the time I get home from work at night, I just don't have the energy."

Now, at age 45, he is recommitting to an exercise routine.

"I just want to be healthy so I can be there for my kids for as long as I can," Marcus said. "I believe I need to have at least four days out of the week with an hour a day -- vigorous exercise , you know, building up a sweat."

Guidelines from the U.S. Department of Health and Human Services suggest 75 minutes of "vigorous" aerobic activity or 150 minutes of "moderate" activity every week for adults.

Vigorous activities include running, jumping rope or playing squash, activities where you can't say more than a few words at a time.

Moderate activities include brisk walking, dancing or biking, where you usually can talk but not sing.

"Exercise makes you live longer," said Dr. Leslie Cho, who directs the Cleveland Clinic's Women's Cardiovascular Center. "It improves your blood pressure, improves your glucose control so you don't get diabetes, your cholesterol level is lower."

Your heart rate is another way to gauge activity level. Start with 220 and subtract your age. Moderate activity is 50 to 70 percent of that number.

For a 50 year old, that's a heart rate of about 85 to 120, according to the Centers for Disease Control and Prevention.

We asked New York Sports Club trainer Alyssa Exposito to help Marcus find his stride.

"I recently got an Apple Watch -- it does have a fitness component," Marcus said.

The problem? "I haven't used it yet."

And the amount of calories he burned taking it out of the box? "Zero," he acknowledged with a laugh.

But if you actually use them, those devices can help you keep track of the 150 minutes of moderate activity you need a week. And it doesn't have to be at the gym.

You can weave exercise into daily activities. For example, if you commute to work, think about walking part of the way if you can.

  • Jonathan LaPook

    Dr. Jonathan LaPook is the chief medical correspondent for the CBS Evening News. Follow him on Twitter at @DrLaPook