Sep 2, 2011 5:47 PM
''If you are overweight or mildly obese and want to lose fat -- belly fat, visceral fat, liver fat -- vigorous aerobic training was better than resistance training," says researcher Cris Slentz, PhD, an exercise physiologist at Duke University Medical Center in Durham, N.C.
The study appears in the American Journal of Physiology, Endocrinology and Metabolism.
Slentz and his team assigned men and women ranging from age 18 to 70, to one of three groups:
The study lasted for eight months.
Slentz focused on visceral fat. It's located deep within the body around the stomach and fills spaces between internal organs. Think of it as "inside fat." It's linked to an increased risk for heart disease, diabetes, and other health problems.
It is different from subcutaneous fat, the kind that lies directly under the skin. Subcutaneous fat is what is responsible for the so-called ''muffin top," the fat that spills over waistbands. Although too much of this subcutaneous fat is not good, too much visceral or "inside" belly fat is much more dangerous.
The researchers compared before-and-after measurements. They reported results for 144 men and women, about equally divided among the three groups.
The aerobic training group had the most visceral fat reduction.
The combination group had more total belly fat reduction than aerobic training alone, but less visceral fat reduction that the aerobic-only group.
The resistance-only group had the least total belly fat reduction. It lost some subcutaneous fat but actually gained a bit of visceral fat.
As for why aerobic training is the better belly fat fix, Slentz says it simply burns more calories than resistance training does. "I really believe that's all there is to it."
The aerobic training was also better than the resistance training at improving risk factors for diabetes, such as insulin resistance, and risk factors for heart disease.
Slentz cautions people who haven't been active to check with their doctor before starting a vigorous exercise program.
The results are no surprise to Mark Tarnopolsky, MD, PhD, professor of pediatrics and medicine at McMaster Children's Hospital, McMaster University Medical Center. He reviewed the findings for WebMD but did not participate in the research.
Aerobic training works better for belly fat, he says, because of higher calorie burn. "There are always rest periods between sets even in a circuit weight training program," he tells WebMD.
"Years ago, we found that the energy cost of a very intense circuit weight training in young men was only about 250 calories an hour," he says. Running for an hour would burn 500 to 750 calories.
He and a colleague are now looking at whether high-intensity sprints could also reduce belly fat.
The results don't suggest people should give up resistance training, he says. It is needed to offset the loss of muscle mass with age and to maintain strength.
"Strength is increasingly important to health and the ability to live independently as we age," he says. "Endurance exercise does little if anything to help with strength loss."
For that reason, he says, a mixture of aerobic and resistance training is best.