A dozen women sat in a circle in a UCLA classroom one recent evening, hashing out the intricacies of fats--those insidious passengers in five-cheese risotto and \o7 creme brulee \f7 that may well be lurking behind the rising rates of certain cancers.

They were educated, accomplished women. They wore bifocals and blazers, badges of professional middle-age. But as the evening wore on, the conversation turned confessional: They talked about dessert the way recovering alcoholics talk about a drink.

Could you eat pumpkin pie without the crust? Could you use mozzarella in macaroni and cheese and have it not be stringy? What to do with that leftover stuffing beckoning from the freezer? Anyone know how many fat grams reside in a chicken-\o7 fajita\f7 pita?

Their monthly version of dietary group therapy is part of a nationwide research project looking into whether women can stick to a low-fat regimen. If they can, a larger study has been proposed to explore, over many years, whether a low-fat diet might cut one's risk of cancer.

The outcome of even this first study remains unclear. As the participants tell it, they lurch between abstinence and overindulgence. But if they succeed in minimizing their fat intake, Marilyn Aronson, who conducted the UCLA session, believes there is much to be gained.

"Diet is not involved in every kind of cancer," says Aronson, a clinical research nutritionist. "But I do believe that there are a lot of people suffering from cancer who might have been able to avoid it, or at least delay it, had they eaten differently."

An estimated one third of all cancer deaths may be related to the food we eat. That's as many as, perhaps more than, can be traced to tobacco. With some 485,000 cancer deaths in the United States each year, that means 160,000 people will die of cancers traceable to diet.

Yet, precisely what it is in foods that promotes cancer or protects against it remains unclear. The question is hotly debated. Most researchers agree that alcohol consumption and obesity play a central role in certain cancers. But beyond that, there is little consensus.

Dietary fats are a prime suspect. They have been linked to cancers of the colon, breast, prostate and lining of the uterus. But research on the relationship between fats and cancer is contradictory, and some experts believe the problem may be calories, not fats.