When Neal Barnard was growing up in the 1960s, he witnessed the devastation of diabetes firsthand through his father, a physician who specialized in the disease. "I can't tell you now many people I saw going blind, suffering heart attacks and having their legs amputated," he says. Barnard's father had one treatment to offer patients--insulin. Now that Barnard is an M.D. himself, he's trying a different approach. He's putting patients on an aggressive vegetarian diet in the hope of actually reversing type 2 [adult-onset] diabetes. "I want to turn the clock back so that patients can go off diabetes medications," he says.

That may not be as farfetched as it sound. The famed diet doctor Dean Ornish has shown that a strict lowfat diet and exercise can reverse heart disease. Why not diabetes? A leading risk factor for Type 2 diabetes is obesity. As Americans girth has expanded, disease rates have spiralled. Today, 16 million Americans have this disorder, costing the United States $100 billion a year. But new research shows that diet and exercise can not only help prevent the disease, but also possibly delay its progression. "With the right diet and fitness framework, we might really be able to modify the course of diabetes," says Dr. Francine Kaufman, president of the American Diabetes Association.

Diabetes is a progressive disease, but lifestyle changes can help at every stage. People with diabetes have trouble regulating blood sugar levels. Normally, the naturally occurring hormone insulin helps move glucose out of the bloodstream and into cells, which need the sugar for energy. But in many obese adults--and increasingly, overweight teenagers--cells stop responding properly to insulin. Blood sugar build up and eventually damages blood vessels and other tissues. Although supplemental insulin and insulin-boosting drugs are needed in advanced diabetes, patients with mild cases can often normalize their blood sugar with diet and exercise. The ADA advocates a diet of whole grains, fruits and vegetables with smaller portions of lean meat, fish, and dairy.

But Barnard, an adjunct professor at George Washington University, contends that to see reversals in diabetes, more drastic steps are necessary. In a small pilot study, he put seven patients on a strict vegan diet. Patients derived 75 percent of their calories from carbohydrates in the form of whole grains, vegetables, fruit and beans. Meat, cheese, and eggs were off-limits, since some scientists believe their saturated fat and high calories increase insulin resistance. After 12 weeks, the vegan patients showed an average 28 percent reduction in fasting blood sugar versus a 12 percent reduction in the control patients who followed the ADAdiet. "Most of the vegan group were able to reduce their medications," adds Barnard. "None of the controls did." But such a small trial is hardly conclusive, and Barnard is repeating the trial now in a larger group of 68.

Barnard did not include an exercise regimen in his study, because he wanted to isolate the effects of diet. But for people with diabetes, exercise is crucial; active muscles absorb glucose more efficiently. The combination of diet and exercise is more powerful than either one alone and may be even more effective than drugs, at least in preventing diabetes. A landmark trial of 3,234 pre-diabetic patients last year found that a lowcalorie low-fat diet and moderate exercise--30 minutes five times a week--reduced new diabetes cases by 58 percent over a three-year period. By contrast the drug metformin, which boosts insulin sensitivity, reduced new cases by only 31 percent.

Even with diet and exercise, not everyone will be able to roll back diabetes. After a certain point, the body simply cannot produce enough insulin. In such advanced cases, however, diet and exercise may still help prevent some of the worst effects o the disease--heart attacks and strokes. The NIH is launching a 12-year 5,000-patient study to test the idea. If it proves successful, it would not only reduce the nation's $100 billion burden, but also relieve untold human suffering.