Vigorous exercise reduces the risk of diabetes among overweight, sedentary men, study findings suggest. And if these men reduce the amount of calories they consume each day, their diabetes risk drops even further.

“Taking up regular exercise, improving diet and losing weight are simple ways of preventing diabetes,” study author Dr. Kay L. Cox, of the University of Western Australia told AMN Health.

“The findings are important as the incidence of overweight and diabetes are on the increase in western countries,” she said. “We need to put prevention programs in place now before it is too late.”

For their study, Cox and her colleagues asked 60 nonsmoking, sedentary, overweight 20-to-50-year-old men to either maintain their usual diet or restrict their calorie intake for 16 weeks. The men, all non-diabetics, were also randomly assigned to participate in a vigorous exercise group or light exercise group, for comparison.

Overall, the researchers found that vigorous exercise - intense half-hour-long sessions three times per week - alone lowered glucose levels by 13 percent and insulin levels by 20 percent in response to an oral-glucose-tolerance test, they report in the American Journal of Clinical Nutrition. For this glucose test the researchers measured how much insulin was needed to keep glucose concentrations within a certain desirable range two hours after the men consumed a sugary drink.

Fasting glucose levels were also lower among the vigorous exercisers in comparison to their light-exercising peers, the researchers report.

“The main point of the study is that exercise was able to reduce blood glucose and insulin levels in men with normal levels,” Cox said. “This means there is a potential protective effect of regular exercise to reduce the risk of diabetes.”

The vigorous exercisers did not have any great weight loss, however, the researchers note.

Calorie restriction was also effective, the report indicates. Men who restricted their calorie intake not only lost a significant amount of weight and had a nearly six percent reduction in body fat, but their insulin concentrations were also reduced by 40 percent on the glucose tolerance test.

Further, when calorie restriction was combined with vigorous exercise, the two worked together to lower insulin levels after the glucose test, the report indicates.

Altogether, the findings show that “even taking up exercise after being sedentary can improve health,” Cox said.

She advises that sedentary individuals slowly build up their exercise level from light to moderately intense. “They should find an activity that they like and that they will keep doing,” she said.

Those who are overweight should start with swimming, cycling, or some other non-weightbearing exercise to minimize their risk of joint problems, the researcher added. “They should also try to lose weight by cutting down on the amount they eat, substitute high fat foods with low fat foods and include fruit and vegetables rather than refined carbohydrates.”

“Even if weight is not lost but people exercise regularly they may also gain the benefits in terms of improving glucose levels,” Cox said.

SOURCE: American Journal of Clinical Nutrition, August 2003.