DURHAM, N.C. -- Inactivity leads to significant increases in visceralfat, and a moderate exercise regimen can keep this potentiallydangerous form of fat at bay, according to the results of the firstrandomized clinical trial evaluating the effects of exercise amount andintensity in sedentary overweight men and women.
Additionally, the Duke University Medical Center researchers foundthat increasing amounts of exercise can reduce visceral fat. In termsof overall weight gain, the patients who did not exercise would gainapproximately four pounds per year, the researchers said.
Visceral fat, the form which accumulates around the organsinside the belly, particularly concerns physicians because increasedlevels have been associated with insulin resistance, cardiovasculardisease and other metabolic syndromes. Visceral fat is located deeperin the body than subcutaneous fat, which lies just under the skin.
"In our study, the control group that did not exercise saw asizable and significant 8.6 percent increase in visceral fat in onlysix months," said Duke exercise physiologist Cris Slentz, Ph.D., leadauthor of a study published in the October issue of the Journal ofApplied Physiology. "We also found that a modest exercise programequivalent to a brisk 30-minute walk six times a week can preventaccumulation of visceral fat, while even more exercise can actuallyreverse the amount of visceral fat.
"We believe that these results shine a clear spotlight on thehigh costs Americans are paying for their continued inactivity," Slentzcontinued. "I don't believe that people in general have gotten lazier-- it's more that they are working too hard or are at their desksworking on computers with fewer opportunities for exercise. Thesituation is out of balance."
The modest exercise program cited by Slentz is consistent withthe latest recommendations by the Centers for Disease Control andPrevention and the American College of Sports Medicine. However, Slentzbelieves that the public health message needs to be modified,especially for a country where two out of three adults are overweightor obese.
"Until we are able to prevent the weight many dieters regainfollowing short-term dieting success, we should place a greaternational emphasis toward prevention," Slentz said. "It will be achallenge to change the message from 'exercise now to lose weight' to'exercise now so in five years you won't be 20 pounds heavier.'"
To better understand the effects of differing amounts ofexercise, the researchers studied 175 overweight sedentary men andwomen who were beginning to show signs of lipid problems. They wererandomized into one of four groups: no exercise, low dose/moderateintensity (equivalent of 12 miles of walking per week), lowdose/vigorous intensity (12 miles of jogging per week) or highdose/vigorous intensity (20 miles of jogging per week).
Since the trial was designed solely to better understand therole of exercise, patients were told not to alter their diet during thecourse of the trial, which lasted six months for the group that did notexercise or eight-months for the exercise groups. The additional twomonths for the exercise group came at the beginning of trial, whenparticipants slowly ramped up their exercise to their designatedlevels.
The exercise was carried out on treadmills, elliptical trainersor cycle ergometers in a supervised setting. The researchers usedcomputed tomography (CT) both before the exercise program began andeight months later to determine the extent and distribution of fatchange.
"There were no significant changes in visceral, subcutaneous ortotal fat in either of the low exercise groups for men or women, whichsuggest that this amount of exercise is adequate to prevent significantgain in fat around the stomach, and that the amount of exercise is moreimportant than the intensity," Slentz said.
"On the other hand, participants who exercised at a levelequivalent to 17 miles of jogging each week saw significant declines invisceral fat, subcutaneous abdominal fat and total abdominal fat,"Slentz continued. "While this may seem like a lot of exercise, ourpreviously sedentary and overweight subjects were quite capable ofdoing this amount."
Specifically, those participants exercising at the highest level saw a6.9 percent decrease in visceral fat and a 7 percent decrease insubcutaneous fat.
The Duke team was led by cardiologist William Kraus, M.D., whoreceived a $4.3 million grant from the National Heart, Lung and BloodInstitute in 1998 to investigate the effects of exercise on sedentaryoverweight adults at risk for developing heart disease and/or diabetes.The results of that five-year trial, known as STRRIDE (Studies ofTargeted Risk Reduction Interventions through Defined Exercise), andother analyses of the data collected, began to be published in 2002.
The Duke team is currently enrolling patients in STRRIDE II, inwhich researchers are seeking to determine the effects of weighttraining, alone and in combination with aerobic training, oncardiovascular health.
Joining Slentz and Kraus were Duke colleagues, Lori Aiken,Connie Bales, Ph.D., Johanna Johnson, and Brian Duscha. Joseph Houmard,Ph.D., and Charles Tanner from East Carolina University, were alsomembers of the team.
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