Low-carb beer, sugar-free candy and zero-carb chocolate all sound like a dieter's dream in these days of government alarms over obesity.

But nutritionists point out that there's no free lunch, and that some of the new products showing up on supermarket shelves are not necessarily low-calorie.

With the low-carbohydrate fad created by the Atkins diet still raging _ and claiming more than $1.1 billion in food sales this year _ manufacturers have produced an astonishing array of new products. Many put creative use to a class of food ingredients called "sugar alcohols," which processors contend can take the guilt out of "guilty" goodies such as ice cream, cheesecake, brownies, cookies and beer.

Sugar alcohols aren't found in many household kitchens, but are natural products found in fruits and berries. They get the name because their chemical structure partly resembles both that of sugar and alcohol.

Mary Ellen Camire, a professor of nutrition at the University of Maine, said sugar alcohols aren't chemically classified as sugars, and so can be marketed in products that are advertised as "sugar-free."

Sugar alcohols have been around for years and were previously used in making food for diabetics and others who must reduce sugar intake, Camire said. One advantage: They are absorbed slowly into the body and don't increase the sugar counts in the blood. But Camire said the slow absorption is a problem for some people, who end up with diarrhea if they eat too much of the product.

Camire said sugar alcohols are an attractive substitute for sugar because they are a bulking agent, adding fiber and substance to products, and have qualities that permit piecrusts to brown as if they had real sugar in the ingredients. Artificial sweeteners do not have these qualities, she said.

"But they are not zero calories," she said, explaining the products are lower in calories but are definitely not calorie-free.

Malitol, the most commonly used sugar alcohol, provides about 2.5 calories for every gram eaten _ about half of the 4 calories per gram provided by sugar. Other common sugar alcohols appear on content labels as sorbitol, xylitol, lactitol, isomalt or hydrogenated starch hydrolysates.

Look for more products to come. Information Resources, a company that monitors consumer trends, says there's no sign the Atkins fad is waning and estimates that 26 million Americans are on low-carb diets. Another 70 million are limiting their carb intake, according to the company. Sales of low-carb products increased 5.8 percent in the last year, outpacing a 1.7 percent growth in total food and beverage sales.

Lilian Were, an assistant professor of nutrition at Chapman University in Orange, Calif., said many products are making creative uses of sugar alcohols, which had only limited uses in the past, such as sweeteners in sugar-free gum and toothpaste. "It's a good marketing strategy," she said.

Bonnie Liebman, a nutritionist with the Washington-based Center for Science in the Public Interest, said one problem is that federal regulators don't provide a definition of what "low-carb" might mean.

Liebman's group has petitioned the U.S. Food and Drug Administration to start regulating carb claims, just as the agency regulates what constitutes "low-calorie" or "low-fat" in advertising claims.

Liebman said many consumers are deceived into believing that low-carb products are lower in calories, or that low-carb calories don't count.

"Minimal impact on carbohydrate levels does not mean minimal impact on your hips," she said.

She said dieters buying the products in hopes of losing weight are destined to re-learn the harsh lessons of the fat-free-food fad of the 1990s: You can easily get fat eating fat-free ice cream.

The FDA has not responded to the petition, but it has warned some manufacturers that their carb claims don't stand up to much scrutiny.

In January, the agency told Russell Stover Candies that its "low-carb" toffee squares and pecan delights were improperly labeled.

Felicia Satchell, director of the FDA's food-labeling division, said the carb savings on the Russell Stover products were not much different from conventionally made candies. The agency said the low-carb toffees and pecan delights still contained 22.9 grams of carbohydrates, compared to ranges of 16 to 25 found in comparable treats that competitors made the conventional way.