Campus News

Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338

News Release

June 17, 2004

Small lifestyle changes can help prevent type-2 diabetes, says prof

Obese males are at a huge risk for type-2 diabetes – the most common form of diabetes in Canada – but a University of Guelph professor has found they can change their insulin sensitivity with only 12 weeks of moderate exercise and a small reduction in daily calories, according to research published today in the American Journal of Clinical Nutrition.

Human biologist Terry Graham and graduate student Heather Petrie found that obese males aged 20 to 35 who began walking for about an hour every other day and eating the equivalent of two fewer slices of bread a day increased their insulin sensitivity by 60 per cent.

“Twelve weeks was all it took to decrease their insulin levels, making them more sensitive to insulin so they don’t have to produce as much of this vital hormone to regulate the body's blood glucose,” said Graham, lead author of the study. “That means if obese individuals can either exercise or achieve weight loss through diet, they can fairly quickly induce insulin sensitivity.”

Obese individuals have a resistance to insulin and require higher levels of insulin to adjust their glucose levels, putting them at great risk for type-2 diabetes. Although it is preventable, type-2 diabetes accounts for 90 per cent of the diabetes in Canada, and about a third of adults with diabetes are unaware that they have the condition. Those with the disease can’t produce enough insulin to regulate the body's blood glucose and they often have to take drugs to help manage blood sugar levels.

In previous studies, Graham has found that caffeine decreases the ability of insulin to regulate lean individuals’ blood glucose. In this study, he wanted to determine if caffeine would make the obese men even more resistant to insulin and to what degree exercise and weight loss could change that resistance.

When the participants ingested caffeine followed by a carbohydrate drink, they did have an increased resistance to insulin, but “the biggest change in their insulin sensitivity came from our exercise and weight loss intervention,” said Graham.

When looking at the insulin sensitivity index, the higher the number, the better the fuel economy, said Graham. Typical insulin levels of lean individuals sit between 10 and 12. After they have caffeine, the levels drop to eight. At the beginning of the study, the obese participants’ levels were only five and would drop to four after having caffeine. After the short period of controlled weight loss and exercise, their levels rose to eight. “They’re still not as well off as a lean individual, but in three months, we reversed the levels they probably had for 20 years,” said Graham.

Each participant ate 300 fewer calories a day and burned 500 calories by walking briskly on a treadmill for about an hour every other day. They were told not to exercise outside of the lab, so the results could be monitored. “The average individual lost a little over eight kilograms, or 18 pounds, in the 12 weeks,” said Graham. “It was a controlled systematic decrease in body weight and fat.”

Caffeine still resulted in increased insulin resistance following the exercise and diet intervention, with participants’ levels dropping to six from eight after having caffeine. “They were still sensitive to caffeine, but they’re still better off than at their pre-weight loss levels,” said Graham. “This is a clear example of how adopting a positive lifestyle can improve one’s health.”

Terry Graham
Human Biology and Nutritional Sciences
(519) 824-4120, Ext. 56168, or

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