THURSDAY, Sept. 25 (HealthDay News) -- In people with type 2 diabetes, regular aerobic exercise and weightlifting may reduce levels of fat in the liver by as much as 40 percent, according to Johns Hopkins researchers.

High liver fat levels are common in type 2 diabetes patients and contribute to heart disease risk.

The study included 77 diabetic women and men who were divided into two groups. For six months, one group did three 45-minute sessions of moderate aerobic exercise (bicycling, running on a treadmill, or brisk walking) and three 20-minute sessions of weightlifting per week. The other group didn't do any formal aerobic fitness or gym classes.

MRI scans showed that people in the exercise group had lower levels of liver fat by the end of the study (5.6 percent) than those in the non-exercise group (8.5 percent).

The exercise group also had better fitness and less body weight and fat than those in the non-exercise group. Those who did the aerobic/weightlifting program: had 13 percent higher averages for peak oxygen uptake levels during treadmill testing; were 7 percent stronger; had 6 percent lower body fat and body weight; and had 2-inch smaller waistlines (an average of 39 inches vs. 41 inches).

"The benefits in improved fitness and fatness are clear, and physicians should really have all people with type 2 diabetes actively engaged in an exercise program," lead investigator Kerry Stewart, a professor of medicine and director of clinical and research exercise physiology at the Johns Hopkins School of Medicine and its Heart and Vascular Institute, said in a Hopkins news release.

The findings were presented Sept. 18 at the American Association of Cardiovascular and Pulmonary Rehabilitation annual meeting, in Indianapolis.

"People with type 2 diabetes have added reason to be active and to exercise, not just because it is good for health, but also because our study results pinpoint a key benefit to trimming the fatty liver that complicates their illness and which could accelerate heart disease and liver failure," Stewart said.

About 14 million Americans have type 2 diabetes.

More information

The American Diabetes Association has more about type 2 diabetes.