Edward Weiss, Ph.D., conducts treadmill tests as part of his ongoing research comparingthe benefits of exercise, diet or a combination of both. Photo by Sara Savat
Exercise is more effective than diet in reducing fat between muscles and in the abdomen between organs (visceral fat), according to Saint Louis University research published in the Journal of Applied Physiology.
According to researcher Edward Weiss, Ph.D., assistant professor of nutrition and dietetics at Saint Louis University, study participants who lost weight through exercise alone had a nearly two-fold greater reduction in intermuscular and visceral fat than study participants who lost comparable weight through diet.
"Our research demonstrates the importance of frequent, vigorous exercis e, such as a brisk hour-long walk each day, in reducing some of the especially unhealthy fat deposits in the body," Weiss said.
High levels of intermuscular and visceral fat are associated with insulin resistance, a condition in which the body struggles to regulate blood sugar levels that often leads to type 2 diabetes. Conversely, both weight loss and exercise, regardless of weight loss, are independently associated with improved glucoregulation, or blood sugar control.
Because study participants in the exercise group lost weight and exercised, researchers expected to see a greater improvement in glucoregulation in the exercise group than in the diet group. However, both groups experienced similar improvements in glucoregulation.
"We have a few theories that may explain why the exercise research group did not see a greater improvement in glucoregulation," Weiss said. "We performed the follow-up testing two days after the last exercise bout, so it is possible that the exercise effect, which might be short-lived, may have worn off. Another explanation would be that diet affects more than just one's weight. It's possible that physiological changes in the intestines caused by diet improved glucoregulation."
Weiss is studying both of these possibilities in his current research, which will compare the effects of diet, exercise or a combination of diet and exercise in improving overall health, disease risk and aging. Learn more about the study here: http://www.slu.edu/x38037.xml
Altogether, 39 participants completed the one-year study. Study participants were sedentary 50-60 year old men and post-menopausal women with a body mass index of 23.5-29.9. They had no history of diabetes or other health issues including high blood pressure or coronary heart disease.
Study participants were randomly assigned to one of three groups: an exercise group, diet group and a control group. With the help of dietitians, participants in the diet group decreased their calorie intake by 16 percent during the first three months and by 20 percent during the remaining nine months of the study. Personal trainers helped participants in the exercise group increase their energy expenditure by 16 percent in the first three months and by 20 percent during the remaining nine months of the study. Study participants in the control group had access to general diet information and yoga classes, but received no formal coaching.
Study coauthors include Joan C. Murphy, Jennifer L. McDaniel and Katherine Mora from Saint Louis University; Dennis T. Villareal from Washington University School of Medicine; and Luigi Fontana from , Washington University School of Medicine and Istituto Superiore di Sanita in Rome, Italy.
The study was supported with grants from the National Institutes of Health and the National Institute of Diabetes, Digestive and Kidney Diseases.