The findings are the result of a six-month study of 150 participants, each of whom was designated as having pre-diabetes based on elevated fasting glucose levels.
Study participants were randomised into four groups. The first group followed an intervention modeled after the Diabetes Prevention Programme (DPP), considered a gold standard, that aims to achieve a 7 per cent body weight reduction over 6 months.
The programme requires cutting calories, eating a low-fat diet, and exercising. Study participants in this group adopted the diet changes, and performed moderate-intensity exercise equivalent to 12 km of brisk walking in a week.
"We know the benefits of lifestyle changes from the DPP, but it is difficult to get patients to do even one behavior, not to mention three," said William Kraus, professor of medicine at Duke University School of Medicine in the US.
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"We wanted to know how much of the effect of the DPP could be accomplished with exercise alone, and which intensity of exercise is better for controlling metabolism in individuals at risk for diabetes," Kraus said.
One of the exercise-only groups came in a close second. Participants in the moderate-intensity, 18.5 km group saw a 7 per cent improvement in glucose tolerance on average. The moderate-intensity, 12 km group had a 5 per cent improvement on average.
The lowest improvement was seen among those in the vigorous-intensity, 18.5 km group, with only a 2 per cent average improvement.
"High-intensity exercise tends to burn glucose more than fat, while moderate-intensity exercise tends to burn fat more than glucose," Kraus said.
"We believe that one benefit of moderate-intensity exercise is that it burns off fat in the muscles, which relieves the block of glucose uptake by the muscles, he said.
"That's important because muscle is the major place to store glucose after a meal," Kraus said.