TUESDAY, April 10 (HealthDay News) -- Many obese Americans who try to lose weight are successful, at least short-term, using traditional methods, according to a new study.

Researchers who evaluated the strategies of more than 1,500 successful obese dieters found that eating less fat, exercising more, taking prescription diet pills and joining a commercial weight-loss program led dieters to lose from 5 percent to 10 percent or more of their body weight.

Just as important as picking a strategy for losing weight is a dieter's commitment to the approach, whatever it is, said lead investigator Dr. Jacinda Nicklas, a clinical research fellow at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston.

"Any of these strategies takes a certain degree of investment -- cutting back on calories, exercising on a regular basis, going to the doctor to get a prescription weight-loss drug, joining a program," she said.

More than a third of Americans are obese. While many obese people may think attempting to lose weight is futile, Nicklas said her study suggests that is not true. And for an obese person, weight loss of 5 to 10 percent can produce health benefits, such as lower blood pressure, she said.

The study, published online April 10 in the American Journal of Preventive Medicine, looked at a nationally representative sample from the 2001 to 2006 U.S. National Health and Nutrition Examination Survey. This ongoing survey collects information about health, health behavior and other data.

The survey takers computed the participants' body mass index (BMI), based on their reported height and weight. BMI is a measurement of size used to calculate weight categories, from underweight to obese. The team focused on the data from those with a BMI of 30 or above, considered obese.

Respondents were asked if they had tried to lose weight and, if so, how they tried to do so.

Of more than 4,000 obese respondents, more than 2,500 said they had tried to lose weight in the last year. Of these, about 1,000 (40 percent) said they had lost 5 percent or more of their body weight. More than 500 (20 percent) said they had lost 10 percent or more.

"For the 5 percent weight loss, people said they used one or more of these strategies -- eating less fat, exercising more and using prescription weight-loss drugs," Nicklas said. "For the 10 percent loss, it was any one or more of those and also joining a commercial weight-loss program."

Other methods, such as liquid diets, nonprescription diet pills or fad diets, were unsuccessful, the researchers said.

"Something advertised over the Internet that seems quick and easy may seem to be an easier way to lose weight but we don't have any evidence that those methods work," Nicklas said.

The study has limitations, however, she said. Height and weight were self-reported, and there is no follow-up data on whether the dieters kept off the pounds.

The results do offer some hope, said Dr. Jennifer Marks, a professor of medicine at the University of Miami Diabetes Research Institute, who is familiar with the study.

The message is, "Weight can come off," she said.

Of those surveyed who were obese and trying to lose weight, about 70 percent were white, so the findings may not apply as much to other ethnicities, she said.

For her patients trying to lose weight, Marks said she advises them to consider the possible strategies and to the one or two that seem "least onerous to you."

With her own patients, Nicklas has noticed yet another strategy used by some successful dieters who want to maintain the loss. They take on a new ''persona." For instance, some become triathletes who are eager to maintain that new image.

These people seem to maintain the loss better, she has observed.

More information

For more about weight control, visit the U.S. National Institutes of Health.