TUESDAY, May 3 (HealthDay News) -- A structured exercise program helped people with type 2 diabetes lower their blood sugar level more effectively than just receiving advice about getting more physical activity, according to a new review of data.

After analyzing the results of 47 randomized clinical trials, the researchers also found that exercising for longer periods of time was better at bringing blood sugar levels down than exercising more intensively.

"People with type 2 diabetes should engage in regular exercise training, preferentially supervised exercise training," said the study's senior author, Dr. Beatriz Schaan, a medical school professor at the Hospital de Clinicas de Porto Alegre in Brazil. "If these patients can perform training for more than 150 minutes per week, this would be more beneficial concerning their glucose control. However, if they cannot reach this amount of weekly exercise, lower exercise amounts are also beneficial."

Results of the study are published in the May 4 issue of the Journal of the American Medical Association.

The clinical trials included in the current analysis included more than 8,500 participants. The studies used a measure known as hemoglobin A1C (HbA1C) to assess a particular treatment's effectiveness. HbA1C, sometimes just called A1C, is a measure of long-term blood sugar control. It provides an average of blood sugar levels over a two- to three- month time period. The results of this test are expressed in terms of a percentage. Generally, less than 6 percent is considered normal. People with diabetes usually have levels higher than this. The American Diabetes Association recommends that people with diabetes strive to lower their HbA1C levels to less than 7 percent.

Currently, exercise guidelines recommend that people with type 2 diabetes perform at least 150 minutes a week of moderate-intensity aerobic exercise, and resistance training, such as weight lifting, three times a week, according to the study.

"We always tell patients, even those without diabetes, that it's important to exercise, but we don't tell them how. We don't provide a good structure on what to do," said Dr. Joel Zonszein, director of the clinical diabetes center at Montefiore Medical Center in New York City. "It would be good if we were able to prescribe an exercise program for our patients to follow."

The current analysis compared a group of people with type 2 diabetes who participated in a structured exercise program with a control group that received advice about exercise. A structured exercise program was one that engaged people in planned, individualized exercise. All of the structured programs were supervised.

People in the exercise advice-only groups were told that they needed to exercise and were given advice on how to do so, but they were not engaged in a supervised program, or they were involved in a partially supervised program, according to the study.

People in structured training classes that included both aerobic and strength training lowered their HbA1C by 0.67 percent more than control participants. And structured exercise programs that lasted more than 150 minutes per week resulted in an average drop of 0.89 percent over control participants.

Physical activity advice programs, on the other hand, had an average HbA1C reduction of 0.43 percent versus controls. When combined with dietary advice, physical activity advice lowered HbA1C levels by 0.58 percent over the controls.

"Exercise improves insulin sensitivity; it makes insulin work better," explained Zonszein.

In an accompanying editorial, Dr. Marco Pahor from the University of Florida, Gainesville, suggested that insurance companies should consider paying for the costs of structured exercise programs or fitness center memberships. He notes that in one study, when older adults went to a gym two times or more a week for two years, they incurred $1,252 less in health-care costs than their less-active counterparts.

"Given the health benefits of physical exercise on diabetes prevention, managing type 2 diabetes in patients, and on improving the health of the general adult and older population, it may be time to consider insurance reimbursements for structured physical exercise programs," wrote Pahor.

Zonszein agreed that insurance reimbursement for structured physical activity is a good idea. "It's important, but it's not something that our current system pays much attention to. We pay for diabetes-related dialysis and heart surgeries, but not for exercise to prevent the complications," he said.

More information

Learn more about exercise and diabetes from the American Diabetes Association.