By Patricia Hagen

Low carb. Net carbs. Reduced carb. Carb lite. Carb smart. Carb free.

All sorts of claims are emblazoned on products marketed to the 40 million Americans on low-carbohydrate eating plans.

The problem is, no one knows exactly what the terms mean.

"Some people get confused about net effect carbs," which is what many low-carb dieters count instead of total carbs or calories, says Heather Johnston, who works at a Blimpie Subs & Salads on the Far Northside.

"We talk a lot about it with customers," especially regulars who like the store's low-carb menu, says Johnston, who says she's lost 80 pounds by counting carbs.

Even advocates of low-carb diets and manufacturers can't agree on what "low" means or which carbs should be counted.

Part of the problem is that there is no official definition of "low carbohydrate" and similar terms.

The U.S. Food and Drug Administration defines "low fat" (3 grams or less per serving) and "low sodium" (140 mg or less per serving) and many other nutrition terms. But it does not define "low carbohydrate."

Not yet.

The issue is expected to come up Feb. 12 when the FDA's Obesity Working Group reports to the agency's commissioner, according to the agency. This could start the long process of requesting public comment, writing regulations and requiring new information on labels.

On Monday, the Grocery Manufacturers of America asked the FDA to provide guidance to food companies on low-carb claims. The Center for Science in the Public Interest, a consumer advocacy group, also has requested definitions and guidelines to make labels more accurate and helpful to shoppers.

In the meantime, confusion reigns.

"Not everything out there that says 'low carb' is 'low carb,' " says Regina Schumann, chief operating officer of the Carbohydrate Awareness Council, a trade group for the controlled-carbohydrate industry. Some manufacturers, she says, have been known to print "low carb" on the front of a product, even though the required Nutrition Facts label on the back says sugar, a carbohydrate, is one of the primary ingredients.

Susie Sark, manager of the LoCarb USA Marketplace, 4825 E. 96th St., says she has to screen products carefully to make sure they are truly low in carbohydrates. "I want to make sure my customers are getting what the label is telling them," she says.

Much of the confusion among dieters and manufacturers is over which carbs should be counted.

Some people add up "total carbohydrates" to determine their daily intake. Others count only "net effective carbs" (net carbs, for short).

To get net carbs, most dieters subtract the grams of fiber and the grams of sugar alcohols from the total carbs. The fiber, they say, doesn't count because it isn't digested. They say the sugar alcohols, such as maltitol, don't count because they don't affect blood sugar levels the way sugar and other carbohydrates do.

"Net carbs are terribly confusing," says Syd Ehmke, a Noblesville nurse practitioner who teaches a class on long-term controlled-carb eating. Different food manufacturers, she says, subtract different ingredients to arrive at the net number of grams.

Ehmke, who has lost 20 pounds on a moderately low-carb diet, says net carbs are misleading. The term takes the emphasis off the food's caloric content.

"It smells a lot like 'low fat,' " she says, recalling the days when it seemed all dieters were counting fat grams and would eat a whole sleeve of fat-free cookies thinking they would still lose weight. "I see exactly the same thing happening" with low-carb foods. "You do have to pay some attention" to the number of fat grams and calories in a serving.

So what's a shopper to do until the government and food industry work out some rules?

Nutrition experts on both sides of the carb-cutting debate suggest:

• Read labels carefully.

• Educate yourself about nutrients. Learn about simple and complex carbohydrates, proteins and fats, and which foods pack the most nutrition.

• Be skeptical of advertising and packaging. It's unlikely that a piece of candy really has zero carbs. What's it made of?

• Don't take a relatively low carb count as a license to overeat a food. If you're watching your weight, you also need to consider portion size, calories and fats.

Most traditional dietitians say cutting carbohydrates to extremely low levels is an unhealthful fad that will soon fade away. Yet, low-carb advocates say the method works and it's here to stay.

Low-carb promoters point to recent research studies showing that people can lose weight on low-carb diets without harmful side effects.

But mainstream nutrition groups, such as the American Dietetic Association and the American Heart Association, say the studies were too short to prove that a low-carb lifestyle is safe or effective over the long term.

"People will lose weight on just about any diet they try," says Laura Hartman, a registered dietitian in Carmel. Their cholesterol goes down, she adds, because they lost weight, not because they limited carbohydrates.