A consumer group wants the fake fat olestra to be taken off the market, or severely restricted, on grounds it has made thousands of people sick.

Warning labels for potato chips and other products made with olestra say the zero-calorie fake fat can cause unpleasant gastrointestinal effects, including cramps and diarrhea, and can block absorption of certain nutrients.But the Center for Science in the Public Interest argued Wednesday that those warnings are not enough. Citing a handful of consumers who sought emergency-room treatment for those effects, CSPI said olestra is a "gamble with health."

It has filed petitions with the Federal Trade Commission charging olestra advertising is misleading because it does not disclose side effects. Olestra, sold as Olean, is a synthetic chemical made of sugar and vegetable oil that passes through the body undigested.

Manufacturer Procter & Gamble and Frito-Lay, which makes chips with olestra, vigorously defended the product.

Since 1996, tens of millions of people have eaten more than 500 million servings of olestra-made chips, the companies said. Only about one in 50,000 people report any complaint, and the vast majority are mild stomach upset, they said.