Gonna Pump You Up

Researchers use weight training to reduce insulin resistance, a hallmark of rampant obesity in latino children.

by Alicia Di Rado

In February 2003, Latino kids in Los Angeles tackled a weighty subject: obesity.

Nearly 22 percent of Latino children today are overweight, a condition linked to risk for type 2 diabetes, heart disease and other illnesses.

Scientists have few proven strategies for preventing and treating obesity in these children, but USC obesity expert Michael I. Goran, Ph.D., aims to change that—with strength. Goran, professor of preventive medicine at the Keck School of Medicine, created a program that uses weight training to increase muscle and reduce fat among overweight Latino teenage boys.

The Thrasher Research Fund backed the program through a $365,000, two-year grant, says Goran, associate director of the USC Institute for Prevention Research. Funds supported a 16-week clinical trial of the effects of weight training, also dubbed resistance training, at the Los Angeles Boys & Girls Club in Lincoln Heights.

“Most weight-management programs for youth have tried restricting diet, modifying behavior or giving medications, but these approaches generally have not been successful,” Goran says. “When researchers have tried exercise interventions, they have focused on aerobic exercise, and most of these studies with obese children have led to only a small reduction in body fat and unclear effects on metabolic risk factors.”

In studies of adults, weight training has been shown to offer many metabolic benefits, including improvements in insulin sensitivity, increased muscle mass and reduced fat. This type of exercise also trims visceral fat—fat that surrounds the organs, which is linked to insulin resistance—rather than fat underlying the skin. Fat deposited within muscle fibers also is associated with insulin resistance, he adds.

Yet resistance training has not been adequately tested in overweight kids, and no one has published any studies on the benefits of the exercise in young Latinos.

“We think that by reducing fat and increasing muscle, resistance training will improve insulin sensitivity and decrease risk for type 2 diabetes in overweight teenage boys,” Goran says.

This could make a big difference in Latinos’ health, in particular, because Goran and colleagues have shown that Latino kids are more resistant to insulin than Caucasian children, even after controlling for amount of body fat. One quarter of overweight Latino children have pre-diabetes and face a high risk of developing type 2 diabetes early in life.

Goran and his colleagues recruited 24 overweight Latino teenage boys and put them through about four months of supervised training using machines and free weights. At the end of the study period, the researchers compared the teens’ metabolic risk factors, such as insulin resistance and blood pressure, to those of a control group of overweight teenage boys who did not go through the training program.

Researchers chose to focus on boys because they wanted a uniform group to study, and teenage boys might be more interested in weight training than girls, he adds. He hopes to extend the research to girls in the future.

John Forder, Ph.D., associate professor of research, contributed his expertise in using magnetic resonance imaging to measure fat within muscle. George Salem, Ph.D., assistant professor of biokinesiology and physical therapy, helped design the weight-training programs.

Marc Weigensberg, M.D., assistant professor of pediatrics, provided medical coverage during testing. Geoff Ball, a research associate in Goran’s lab, and Gabriel Shaibi, a doctoral student in biokinesiology and physical therapy, ran study and set up the training.