Less intense exercise may reduce risk of diabetes

Moderate intensity exercise improves pancreatic function more than vigorous exercise, potentially reducing the risk of type 2 diabetes, according to researchers at Duke University Medical Center.

They found that the equivalent of walking 10 miles per week significantly improved how the pancreas functions more than doing the same amount of exercise at a vigorous intensity. Walking 10 miles per week was also better than exercising vigorously for the equivalent of 17 miles per week.

"While these findings may seem counterintuitive, we know that moderate exercise mobilises the body to burn more fat, which may be the mechanism that helps the pancreas work more efficiently," said Cris Slentz, PhD, the study’s lead author and a research scientist at Duke University Medical Center. "Vigorous exercise requires the body to burn more carbohydrates and not as much fat."

Diabetes results from the body being unable to process insulin, a hormone created by the pancreas to control blood sugar levels. While research has shown that exercise improves the body’s ability to use insulin, little has been known about how exercise affects the beta cells in the pancreas that release the insulin.

"Diabetes originates from insulin resistance and beta cell dysfunction," Slentz said. "We know that exercise improves insulin sensitivity (how well insulin works in the body), but the effect of exercise intensity on insulin secretion (pancreas function) is the other piece of this puzzle that needed to be explored."

Inactive, overweight and obese people are generally insulin resistant, but their bodies attempt to maintain a normal blood sugar level by having the pancreas produce more insulin. To better understand why many people in this group go on to develop type 2 diabetes, the research team examined how the beta cells respond to varying intensities of exercise.

"Diabetes is an exercise deficiency disease but little research has been conducted to learn what level of exertion is optimal for regulating glucose levels," Slentz said. "Our findings indicate that moderate intensity exercise appears to be better at improving pancreatic function and as a result, may be better at preventing the progression to diabetes."

The new analysis is published in the October issue of Diabetes Care, a journal of the American Diabetes Association.

The study included more than 230 sedentary, overweight people 40–65 years old who were randomised to a control group or one of three 8-month exercise programs: a low exercise amount at moderate intensity; low exercise amount at high intensity (equal to 10 miles per week) or a high amount of exercise at high intensity (equal to 17 miles per week). Exercises were conducted on treadmills and elliptical trainers. All study participants were monitored to achieve a target heart rate and level of oxygen consumption when active.

While all three exercise programs showed improvements in insulin sensitivity, the moderate-intensity group showed the largest improvement in pancreas function. At the same time, the control group that did not exercise had a significant increase in blood sugar levels, putting them at greater risk for developing diabetes. The researchers caution that the findings need to be further analyzed through additional research conducted over longer periods of time.

The new findings are an analysis from the multi-year, US federally funded study called STRRIDE (Studies of a Targeted Risk Reduction Intervention through Defined Exercise) that examined the effects of varying amounts and intensity of exercise on middle-aged, overweight men and women. The study found that even a modest amount of brisk walking weekly is enough to trim waistlines and cut the risk of metabolic syndrome, an increasingly frequent condition linked to obesity and a sedentary lifestyle.

(Source: Duke University Medical Center: Diabetes Care: October 2009)