The lifestyle changes helped mobile people stay that way and eased severe mobility problems in others, at least over the short term.

Lead author W. Jack Rejeski from Wake Forest University in Winston-Salem, North Carolina, said the trends show the importance of encouraging people to get their weight down and exercise sooner, rather than waiting until they develop problems getting around.

In the new study, published in the New England Journal of Medicine, the researchers calculated that a one-percent drop in weight cut the risk of mobility problems by more than seven percent, and the same increase in fitness level lowered mobility risks by between one and two percent.

"If you can change people's lifestyles sufficiently, they're going to get more mobile and, over time, this will have a tremendous impact on their lives," said Dr. Vivian Fonseca, president of medicine and science for the American Diabetes Association, who wasn't involved in the research.

"There has yet to be really a large study like this that says, 'This really does make a difference,'" Rejeski told Reuters Health, adding that he hopes the results find a way into typical conversations between doctors and their diabetic patients.

Last Updated: 2012-03-28 17:00:10 -0400 (Reuters Health)

The ADA estimates that nearly 26 million Americans have diabetes -- most of them with type 2, the form of the disease often associated with being overweight -- and 79 million more are at risk for developing the condition. Those numbers are expected to increase dramatically as the U.S. population ages.

Diabetics are twice as likely to have mobility problems as other people their age.

Rejeski and his colleagues tested a program in which volunteers were encouraged -- through diet plans, eat-smart strategies, meal replacements and other techniques -- to lose more than seven percent of their body weight. They were also encouraged to exercise at least three hours per week, primarily by walking.

Volunteers in a comparison group were asked to attend group meetings -- focusing on nutrition, physical activity and support -- three times a year.

The study involved more than 5,000 volunteers age 45 to 74, all overweight or obese. They reported their own mobility on health surveys given over four years and took fitness tests at different points during the study period.

After a year, participants in the intervention group had lost an average of six percent of their body weight, compared to less than one percent in the "control" group.

Fifteen percent of people in the no-intervention group had severe mobility problems at the start of the study. That rate increased to nineteen percent after a year, and continued to rise over the next three years.

In the diet and exercise group, thirteen percent started off with severe mobility problems. After a year that fell slightly to twelve percent -- but after that, the likelihood of severe problems began to increase again.

"It's difficult to drag yourself out of that hole," said Rejeski.

For example, some people may regain the weight they lost, "but they also get older, and other things catch up with them," Fonseca, who is also an endocrinologist at the Tulane University School of Medicine in New Orleans, told Reuters Health.

The researchers found that 33 percent of the control group started out with good mobility, a fraction that didn't change much over the next few years.

On the other hand, 37 percent of volunteers in the intervention group started out with good mobility. With diet and exercise, that ratio rose to 41 percent at the one-year mark and, although it declined after that, never fell below the starting point.

Rejeski's team calculated that all in all, the lifestyle changes led to a 48-percent drop in the chance of diabetic patients losing their mobility.

"You don't need extreme amounts of weight loss or extreme lifestyle change to improve your outlook," said Fonseca.

"It is achievable by many people who put their mind to it and who are given the right kind of tools to do that. The problem is, how do we translate this to people outside the study?"

SOURCE: bit.ly/GXsSfJ New England Journal of Medicine, online March 28, 2012.

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