Washington ? A radical ultra low-fat diet and other lifestyle changes may help keep early-stage prostate cancer from worsening, says the first attempt to test the theory.

It’s a small study that tracked men whose tumors weren’t aggressive. Still, the research, published in the September issue of The Journal of Urology, promises to increase interest in whether diet might really help battle cancer.

The study was led by heart-health guru Dr. Dean Ornish and used his famously strict regimen, where people become vegetarians, limit dietary fat to 10 percent of total calories, exercise regularly and learn stress-management techniques such as yoga.

Ornish and fellow researchers at the University of California, San Francisco, recruited 93 men who had decided against treatment for early-stage prostate cancer, a route known as “watchful waiting.”

Half were randomly assigned to the Ornish diet and lifestyle regimen; the others weren’t asked to vary their usual routines. After one year, prostate specific antigen levels had decreased 4 percent in the diet group – unusual for untreated patients – while PSA levels rose by 6 percent in the control group.