A lack of time is one of the main excuses people give for not exercising, but experts say it's easy to sneak exercise into your life.

Melina Jampolis, an internist who works with overweight patients in the San Francisco area, advises clients to squeeze in activity whenever they can. She tells them to do five minutes of calisthenics, such as sit-ups or push-ups, in the morning, take a 10-minute walk at lunch, stand or pace when talking on the phone and march in place while watching commercials on TV.

She also recommends active volunteer work: Coach a Little League team, pack boxes at the food bank, clean up your neighborhood — anything to get you moving and using your muscles.

Jampolis, author of "The No Time to Lose Diet," says one of her female patients started walking dogs at an animal shelter. The activity along with a more healthful diet helped the woman lose 15 pounds.

Many people don't do enough strength training, also called weight training, even though studies show it reduces the risk of many diseases, including Type 2 diabetes, heart disease, cancer and osteoporosis.

To make it easier to sneak some strength training into your life, Miriam Nelson, an exercise scientist at Tufts University in Boston and one of the authors of "Strong Women, Strong Hearts," suggests keeping a set of dumbbells near the TV.

While you are watching your favorite show or the news, do a set or two of different exercises, such as bicep curls, tricep extensions, seated overhead presses, forward fly exercises, side leg raises, ankle exercises, lunges and squats. Try to do strength training several times a week.

Form is important, and you need to challenge yourself, she says. "Strengthening exercises need to be at an intensity where you feel them. They should be moderately hard to hard to get the most benefit."

When traveling, it is best to do body-weight exercises such as push-ups, sit- ups, lunges and squats, she says.

Timothy Church, director of preventive medicine research at Pennington Biomedical Research Center in Baton Rouge, La., says a workout partner helps many people maintain a consistent routine.

"With exercise, it's easy to talk yourself out of doing it and skip it, but it's very difficult to let someone else down."