Link Found Between Sedentary Lifestyle, Insulin Resistance

BALTIMORE -- Getting off the couch and onto the jogging path, or the bicycle, or the treadmill after work may help prevent diabetes, a new University at Buffalo study has shown.

In findings presented here today (June 11) at the annual meeting of the Society for Epidemiologic Research, lead author Jian Liu, a doctoral student in epidemiology in the UB Department of Social and Preventive Medicine, reported that physical activity carried out during leisure-time, but not at work, was associated with a lower incidence of condition know as insulin resistance syndrome, a precursor of diabetes mellitus.

Since leisure-time physical activity is thought to help protect against heart disease, and insulin resistance is a risk factor for heart disease, Liu said the ability of leisure activity to lower insulin resistance may be the mechanism by which exercise protects the heart.

"The important message from this study is that a sedentary lifestyle is not healthy," Liu said. "Being active promotes good health in many ways. Lowering insulin resistance is one more benefit."

Insulin resistance syndrome describes a cluster of metabolic abnormalities -- high blood pressure, high triglycerides, high glucose and low HDL -- that cause cells in the intestinal lining to resist the absorption of insulin.

This study involved data from 7,485 men and 5,856 women between the ages of 20-69 from the Risk Factors and Life Expectancy Study conducted in Italy between 1978-87. As part of the initial data gathering, participants were asked to rate their activity level during work and leisure as sedentary, moderate, heavy or very heavy.

Existence of insulin resistance syndrome was determined from blood-pressure readings and analysis of blood samples taken at the beginning of the study.

Results showed that prevalence of the syndrome was lower in both men and women who were active during their leisure time, but work activity appeared to have no effect. Among the men, the percentages of those having the syndrome jumped from 1.8 percent in the heavy leisure activity group to 3.5 percent in the sedentary group.

Among women, those in the moderately active-leisure-time category had the lowest prevalence of insulin resistance syndrome -- 1.9 percent -- compared to 3.8 percent among sedentary women.

Liu said the study implicates insulin resistance as a potential link between the beneficial effects of leisure-time activity on coronary heart disease risk, and that leisure time spent in sedentary pursuits is an independent risk factor for insulin resistance syndrome. Researchers are not sure why work activity didn't show a similar relationship, he said.

"Perhaps the activity people pursue outside of work is more vigorous, even if they have physically active jobs," Liu speculated. "We don't know the answer to this question."

Additional researchers participating in the study were Joan Dorn, Ph.D., UB assistant professor of social and preventive medicine; Alessandro Menotti, M.D., of the Risk Factor and Life Expectancy Research Group in Rome, Italy, and Maurizio Trevisan, M.D., professor and chair of the UB Department of Social and Preventive Medicine.