Working out even harder to fight disease

The formula for preventing many chronic diseases, including adult-onset diabetes, is simple: Eat right and exercise.

Federal guidelines recommend at least 30 minutes of moderate activity a day -- or, at the very least, on most days -- to fend off the condition. But new findings suggest that, for older adults especially, it may take more of a sweat to keep the illness at bay.

“There’s a lot of information telling us that exercise is good for us,” said Dr. Robert Rizza, an endocrinologist at the Mayo Clinic in Rochester, Minn. “Perhaps when we’re older, we have to exercise longer or more vigorously.”

Rizza and his colleagues studied the impact of exercise on insulin effectiveness, or sensitivity, in 102 adults ages 21 to 87. Insulin regulates levels of glucose in the body, preventing the sugar from accumulating in the blood. With age, insulin may become less sensitive -- a condition that can make people prone to Type 2 diabetes, particularly if they’re overweight or inactive. Studies show that exercise can boost insulin sensitivity and prevent diabetes. But little is known about how much exercise is needed to protect people of different ages.

To get an answer, the researchers put 65 of the healthy volunteers on a four-month bicycle-training program, then measured their insulin activity four days after the training ended. Insulin activity was improved in younger people, ages 21 to 39, but not those over 40. It also was unchanged in the 37 people in the control group who weren’t included in the bicycle training-program. Previous studies have shown that insulin sensitivity is improved in older people one day after aerobic exercise, said study co-author Dr. K. Sreekumaran Nair. But the current study showed the effect doesn’t last.

Rizza said it appeared that insulin activity had rapidly returned to pre-exercise levels in older adults. The researchers suggested that their findings be considered in designing exercise programs for middle-aged and older adults.

Type 2 diabetes accounts for 90% to 95% of Americans with diabetes -- about 16 million people, according to the American Diabetes Assn. The study was published in last month’s issue of Diabetes, the association’s scientific journal.