Men who manage to stay lean and active as they age may lower their risk of developing heart failure, researchers reported Monday.

In a long-term study of more than 21,000 male U.S. doctors, researchers found that men who were overweight were 49 percent more likely than their lean counterparts to develop heart failure over 20 years. Obese men, meanwhile, faced a nearly 200 percent greater risk than the thin men did.

On the bright side, however, regular exercise seemed to offer some protection against heart failure, regardless of weight, the researchers report in the American Heart Association journal Circulation.

The study found that men who were both lean and regularly active had the lowest risk of developing the heart condition, while those who were obese and sedentary were at greatest risk. But exercise was protective even in men who were overweight.

The findings should give people yet more motivation to exercise and follow a healthy diet, according to lead researcher Dr. Satish Kenchaiah, of Brigham and Women’s Hospital in Boston.

“Adopting a healthy lifestyle, keeping a normal weight, and exercising regularly will go a long way toward reducing one’s risk of heart failure and, in turn, the population burden of heart failure,” Kenchaiah said in a written statement.

“Both staying lean and being fit go hand in hand,” he added.

The findings also show that not only obese men, but also those who are merely overweight, may face a heightened heart failure risk. Past research has linked obesity to heart failure, but in this study, overweight men also had a higher risk than normal-weight men.

“On average,” Kenchaiah said, “in men who are 5 feet 10 inches tall, for every 7 pounds of excess body weight, the risk of heart failure will go up by 11 percent over the next 20 years.”

He and his colleagues based their findings on data from the Physicians’ Health Study, a clinical trial that began in 1982 and included roughly 22,000 male doctors between the ages of 40 and 84. At study entry, none of the men had a history of heart attack, stroke or transient ischemic attacks, or “mini strokes.”

Between 1982 and 2007, a total of 1,109 study participants were newly diagnosed with heart failure. Kenchaiah’s team found that the risk rose in tandem with the men’s body mass index (BMI), a measure of weight in relationship to height - even with a range of other factors taken into account, such as age, smoking and other health conditions like high blood pressure.

Exercise was also independently linked to heart failure risk. Men who said they got any vigorous exercise were 18 percent less likely to develop heart failure than their sedentary counterparts.

An important point, Kenchaiah noted, is that the benefits of staying lean and those of exercise were independent of each other.

“Higher BMI increased the risk of heart failure in inactive as well as active individuals,” he said. “By the same token, the beneficial effect of vigorous physical activity in reducing the risk of heart failure was observed in lean, overweight, and also obese men.”

SOURCE: Circulation: Journal of the American Heart Association, December 23, 2008.