For overweight baby boomers looking for ways to live longer and healthier lives, breaking a sweat might be more important than shedding pounds.
A study in today's Journal of the American Medical Association found that regardless of their weight, people of middle age who remain fit are less likely to die for any reason than their sedentary counterparts. Even obese people benefited from regular, moderate exercise, seeing significant reductions in their risk of heart attack, stroke and other illnesses, the study found.
"Fitness and fatness are two different things," said Dr. Steven N. Blair, a professor at the University of North Texas who was lead author of the paper. "You can be fat and be fit - and if you exercise, you are going to get some protection."
Other doctors agreed that the study highlights the importance of physical exercise for health but warned that Blair's results should not be interpreted as a license to pig out.
"Being extremely overweight seems to be uniformly associated with adverse outcomes," said Dr. Lawrence Cheskin, director of the Johns Hopkins Weight Management Center. "Even with exercise, being obese is a significant risk factor for dying."
Blair said the study was the first to rigorously explore the relative contributions of fitness level and weight to an older adult's risk of dying.
The researchers followed more than 2,600 men and women enrolled in the Aerobic Center Longitudinal Study. Participants' average age was 64, and they were examined between 1979 and 2001 at the Cooper Clinic in Dallas.
Doctors determined participants' fitness level by recording how long they could walk on a treadmill with their heart beating at 85 percent of its maximum rate for their age.
Their percentage of body fat was determined by measuring their body mass index (BMI), a widely used height to weight ratio.
People are considered overweight if their BMI is over 25 and obese if it is over 30. A person who is 5 feet 9 inches tall and weighs 203 pounds, for instance, has a BMI of 30 and is considered minimally obese. Experts typically consider a BMI over 35 as dangerously obese.
When they followed up after 12 years, the Texas researchers found that 450 of the study participants had died from a variety of causes. The vast majority - 75 percent - succumbed to cardiovascular disease or cancer.
As expected, the participants' risk of dying increased when they were obese. But the researchers also found that moderate exercise significantly reduced mortality risk, even in volunteers with high BMIs.
The risk calculations were adjusted to account for age, sex, smoking and other factors that might have affected a person's risk of death.
Among those who were moderately obese, the risk of death dropped by 33 percent if the person was fit. For severely obese participants, being fit decreased mortality risk by 74 percent.
"We're not claiming that obesity is good," Blair said. "What I am saying is that if you are obese and fit, your mortality risk is not elevated."
He hoped the finding would counteract popular misconceptions that outward appearance always indicates a person's general health. He noted that many people put on weight as they age, but remain active. Among the obese participants in the study, he said, 46 percent met minimum standards of fitness.
"Often the public discussion stops with fatness, but we tried to go beyond that," he said. "Do you know anyone who is thin and smokes? That person is probably not healthy compared to a fat person who exercises."
The news didn't surprise those on the fitness front lines.
"We have a lot of people who are overweight and are in very good shape," said Ranee Appleby, manager of Brick Bodies health club in Baltimore's Belvedere Square. "They're doing high-intensity classes, doing cardio for quite a lot of time."
Appleby said she hopes the study will help people realize that being in shape means more than shedding pounds.
"They'll quit coming to the gym because they're not losing weight," she said. "All they think of is weight. They need to think in terms of overall wellness."
Sue Guthmann, 61, of Timonium, was relieved to hear that she will see health benefits from her workouts even if she can't lose weight. She described herself as obese and said she has been exercising almost every day at the Maryland Athletic Club for two months on the recommendation of her endocrinologist. She has lost relatively little weight but said she feels much healthier.
"My strength is much better now," she said. "It doesn't tire me walking around."
Experts said someone would be considered fit if they engage in at least 30 minutes of brisk walking or other moderate aerobic exercise at least five days a week.
"If you are so unfit that you can't even walk for 10 minutes, then walk for 5 minutes," Blair said. "The first step is to stand up and start moving."