NEW YORK (Reuters Health) - Moderate exercise like walking may be as good as or better than intense workouts when it comes to certain heart health measures, new research suggests.

In a study of 240 overweight, middle-aged adults, researchers found that moderate exercise, but not vigorous activity, improved participants' levels of blood fats called triglycerides.

Meanwhile, improvements in "good" HDL cholesterol seemed to depend on how much study participants exercised, and not how intensely. What's more, researchers found, both benefits were sustained when exercisers took a vacation from working out.

All of this is good news for sedentary people who would find it hard to leap from the couch to a daily run, according to the study authors.

On the other hand, there's bad news for sedentary people who would prefer to stay that way. In this study, participants who remained inactive saw their "bad" LDL cholesterol levels climb over just six months.

The negative effects don't stop there. Previous work with the same study group found that inactive participants continued to gain weight and inches around the waistline, lead study author Dr. Cris A. Slentz told Reuters Health.

"In overweight or mildly obese sedentary individuals, continuing to be inactive is worse than previously thought," said Slentz, an exercise physiologist at Duke University Medical Center in Durham, North Carolina.

He and his colleagues report the findings in the Journal of Applied Physiology.

The study included 240 overweight, sedentary men and women who were randomly assigned to one of four groups. In two groups, participants worked out intensely on treadmills or other gym equipment, but the amount of exercise varied; one group got the equivalent of 20 miles of jogging per week, while the other logged the equivalent of 12 miles.

A third group exercised at a moderate intensity for a moderate amount of time the equivalent of 12 miles of walking per week. The fourth group remained inactive.

The researchers then looked at the effects each regimen had on participants' cholesterol and triglyceride levels over six months and whether any improvements were sustained after the exercisers took two weeks off.

On average, they found, only the moderate exercisers showed lasting improvements in their triglycerides. Lasting improvements in HDL levels were seen only in exercisers who worked out intensely for a greater amount of time.

The same HDL advantage was not seen among people who exercised vigorously for a lesser amount of time per week. So, Slentz explained, he and his colleagues attribute the benefit to the amount of exercise, and not the intensity.

The bottom line, according to Slentz, is that "most all of the benefits" of exercise are related to the amount, rather than the intensity. An exception is that vigorous exercise, like jogging, is more effective at boosting cardiovascular fitness which, Slentz noted, may or may not be important in heart disease risk.

So a person's choice of exercise should depend on his or her goals, according to the researchers. For many people, that will mean moderate activity.

The "wonderful thing" about such exercise, Slentz said, is that people need only find a couple of 15-minute blocks of time each day to take a walk.