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Study definitive on impact of exercise: Incremental benefits in type 2 diabetes equal to taking one medication

November 8, 2005

By Celia Milne
The Medical Post

The largest trial of its kind shows exercise is an effective treatment for type 2 diabetes.

This was reported by Dr. Ronald Sigal, an associate professor of medicine at the University of Ottawa. Dr. Sigal was the lead researcher in the DARE trial (Effects of Resistance Exercise, Aerobic Exercise and Their Combination on Glycemic Control in Type 2 Diabetes).

"What we have accomplished is finding that if the intervention is delivered, it can do quite a bit. It is worthwhile to get people to do this," said Dr. Sigal, medical director of the diabetes clinic at the Ottawa Hospital.

The DARE trial included 251 previously inactive people from age 39 to 70, with HbA1c (glycosylated hemoglobin) from 6.6% to 9.9%. They were randomized to 22 weeks of either aerobic exercise, resistance exercise, both aerobic and resistance exercise or sedentary behaviour.

At six months, mean HbA1c declined from 7.7% in all groups to 7.2% in the aerobic group, 7.4% in the resistance group and 6.8% in the aerobic plus resistance group. Levels of HbA1c did not change in the sedentary group. Additionally, visceral abdominal fat decreased in all three exercise groups but not in the sedentary group.

Dr. Sigal noted that even slight improvements in blood glucose levels reap big rewards in terms of health. A 1% absolute change in HbA1c translates into a 15% to 20% reduction in the risk for heart disease and at least a 25% to 30% reduction in the risk of microvascular complications, he said.

"Our study is the largest clinical trial to show exercise has an incremental benefit in type 2 diabetes. The benefit would be roughly comparable to taking one medication," said Dr. Sigal.

"We were pleased with what we found but not surprised," added Dr. Sigal, who is also a scientist in the clinical epidemiology program at the Ottawa Health Research Institute.

Exercise and resistance work in the DARE trial took place at local YMCAs and was supervised by personal trainers. Aerobic exercise progressed to 45 minutes three times a week at 75% of maximum heart rate. Resistance training included two to three sets of eight exercises, three times a week. Diet during the study was monitored by a dietitian but was not strict because researchers wanted to isolate the effects of the exercise. "Those who were worse off in the beginning had a more dramatic improvement," said Dr. Sigal.

As the months went by, the trainers' role became more important to the subjects. While it is possible to do aerobic exercise on one's own, he said, resistance training tends not to be done properly if one doesn't go to a facility and get trained.

While it may require a bigger commitment by patients, resistance exercise is a valuable tool because it is likely to increase metabolism while at rest. "The beauty of resistance exercise training with weights is that it provides a persistent effect on insulin sensitivity even a week after the most recent exercise session," said Dr. Sigal.

He pointed out that some diabetes medications lead to weight gain, whereas exercise won't. Exercise also provides cardiovascular benefits beyond reducing blood glucose levels.

One drawback of this type of treatment, of course, is that it is hard work for some people. "This is not generalizable to someone who adamantly refuses to exercise," said Dr. Sigal.

Note: Reproduced with permission from The Medical Post.