The authors of two studies in today's Journal of the American Medical Association say their findings are good news for anyone who doesn't exercise because they don't have time, don't like heavy workouts or can't get to a gym.

"Most of us drive to work, sit at our desks and drive home and watch TV," said Cynthia Gonzalez, who took part in a study at the Cooper Institute of Aerobics Research in Dallas.

The study followed 235 men and women, ages 35 to 60, who were divided into two groups and monitored over two years.

One group spent 20 to 60 minutes vigorously exercising - swimming or biking, for example - up to five days a week. The other incorporated 30 minutes a day of the so-called "lifestyle" exercise.

Researchers found that, at the end of six months, both groups had similar - and significant - improvements in cholesterol ratios, blood pressure and body fat percentages.

However, the lifestyle group had to exercise three times longer than those at the gym to burn the same amount of calories.

The second study, which followed 40 obese women, had similar results.

The studies are among the first clinical trials to find that moderate exercise is beneficial for the one in four Americans who spend most of their time sitting and put themselves at greater risk for heart disease, the leading cause of death in the United States.

"This is great news for the millions of Americans who are not getting enough physical activity," Dr. Claude Lenfant, director of the National Heart, Lung and Blood Institute, said in a statement applauding the two studies.

Before the study, Gonzalez was doing "zero" but found ways to incorporate 30 minutes of moderate exercise - mostly walking - into her routine.

"I'd walk around the house during TV commercials. I'd park farther away at the mall," said Gonzalez, a retired AT&T saleswoman from Garland, Texas, who saw a marked improvement in her treadmill stamina.

Researchers say people who usually don't exercise are more likely to stick to a regimen of doing everyday activities than keep up with a daily gym routine.

"We can all start a program - and most people do in January. And by February, 50 percent of those people have stopped," said Andrea Dunn, a Cooper Institute researcher and lead author of the study.

"If we don't develop approaches that are easier for people . . . we'll continue to have the public-health problem that we have at the moment," she said.

A recent study by the Mayo Clinic suggested that merely moving around or fidgeting can help people stay trim. But these researchers aren't recommending that people stop working out at the gym or saying that a lunchtime walk here and a set of stairs there will do the trick.

"It has to be a little more structured than that. It's not just haphazardly doing 10 minutes on Monday and 10 minutes on Tuesday," said Ross Andersen of Johns Hopkins University, who led the study of obese women.

"And it has to be done at a purposeful pace, " he added.