Researchers at Washington University School of Medicine in St. Louis have found that combining regular exercise with a 10% loss of body weight more than doubles sensitivity to insulin, compared with a 10% weight loss without exercise. Enhanced sensitivity to insulin has important health benefits and likely decreases the risk of Type 2 diabetes and coronary heart disease.
The researchers at the university’s Center for Human Nutrition knew that losing moderate amounts of weight could make people more sensitive to insulin and that exercise alone is not very effective in helping those with obesity and prediabetes lose weight. What they didn’t know was that combining a regular exercise program with a 10% loss of body weight could have such a profound effect on the body’s sensitivity to insulin.
The findings are published June 26 in the journal Nature Metabolism.
“Obesity makes the body resistant to insulin’s ability to decrease glucose production by the liver and increase glucose uptake by skeletal muscle tissue, leading to an increase in blood glucose concentrations,” said senior investigator Samuel Klein, MD, director of the Center for Human Nutrition. “Insulin resistance is a major factor that causes Type 2 diabetes, nonalcoholic fatty liver disease and abnormal blood lipids in people with obesity. We’ve shown that combining exercise with weight loss causes a marked improvement in whole-body insulin sensitivity, thereby lowering the risk of developing diabetes and treating obesity-related metabolic diseases to a much greater degree than is possible with weight loss alone.”
Study volunteers each had a body mass index (BMI) of 30 to 49; 30 is considered obese. Each participant also had prediabetes, with medical evidence of insulin resistance.
A total of 16 people completed the study. Eight were in a diet-only group in which the participants lost 10% of their body weight. The other eight also dieted and lost 10% of their body weight but also were part of a supervised exercise program several days each week.
“The data from most studies show that exercise has very little effect on body weight in people with obesity,” explained Klein, who also is the William H. Danforth Professor of Medicine and Nutritional Science and director of the university’s Division of Geriatrics & Nutritional Science. “Our study involved detailed analyses of metabolic changes in muscle and body fat before and after a 10% weight loss in people who lost weight with diet therapy alone and in those who lost the same amount of weight with diet therapy plus supervised exercise training. The results demonstrate that the benefits of combining exercise with weight loss are considerable.”
More than 37 million people in the U.S. have diabetes, and more than 40% have obesity, which is linked to as many as half of all diabetes diagnoses. It is believed that 96 million people in the United States, about one in three adults, have prediabetes.
“The metabolic benefits we found in this study demonstrate the profound reasons why exercise should always be included in weight-management therapy,” Klein said.