The belly fat you can see may not flatter your figure, but it isn't as harmful to your health as hidden belly fat surrounding internal organs deep in the abdomen. That's the stuff that boosts the risk of heart disease, diabetes and some kinds of cancer. Now, researchers at Duke University Medical Center have shown that the best way to lose this dangerous fat is with aerobic exercise. The Duke team compared aerobic exercise, resistance training (exercising with weights) and a combination of the two during an eight-month study with 196 overweight adults ages 18 to 90. They found that aerobic exercise burned 67 percent more calories than resistance training. It also had beneficial effects on known risk factors for diabetes and heart disease, including elevated liver enzymes, fasting triglycerides and fasting insulin resistance (here, the normal amount of insulin secreted is not sufficient to move glucose into cells - thus cells are said to be "resistant" to insulin's action). No such positive changes were seen in the resistance training group. The aerobic exercise performed in the study was equivalent to jogging 12 miles per week at 80 percent of maximum heart rate.