The business of counting calories is starting to add up.

The national obsession with healthy eating (or at least talking about healthy eating) is translating into a booming business for the companies that restaurants and food processors turn to for performing nutritional analyses of their products.

“More and more restaurants and food manufacturers are looking to meet the needs of health and diet in their consumers,” says Julie Bush, one of the owners of On The Menu, a 2-year-old nutrition analysis company based in Denver.

“There are definitely weeks where we ask each other ’What are we going to do?”’ because they have so much business, says Bush’s business partner, Rebekah Spetnagel. “But it’s a good problem to have.”

Just a few decades old, the nutrition analysis industry first saw strong growth during the 1990s, when the National Labeling and Education Act required companies to disclose foods’ fat, cholesterol, sodium, sugar, fiber, protein and carbohydrate content.

With its Atkins-fueled focus on carbohydrates and other obesity-related issues, the early part of this decade brought another surge for the industry, says Carol Harvey, owner of Palate Works, a San Francisco-based nutrition analysis firm.

Quantifying how this growing demand has changed the industry is difficult. Most nutritional analysis companies are small, there are no trade associations representing it, and some of the larger food companies do their analyses inhouse.

“All I know is there are many more individuals (and) companies in this field now than 10 or even five years ago,” says Harvey.

For her company, business has increased steadily since she started 15 years ago, and particularly picked up last year, when the government began requiring the labeling of trans fats, a type of hydrogenated oil studies have linked to heart disease.

Companies such as Harvey’s typically offer a range of services, including analyzing restaurant menu items, creating nutrition labels for food manufacturers, and reviewing labels to ensure compiance with regulations.

Most analyses are done using readily available software, though sometimes products must be sent out to specialized laboratories which do a more costly chemical analysis (for example, a product is so new that no precedents exist for measuring its components).

A typical software analysis of a product can cost anywhere from $40 to $150, which covers the analysis and a standard federally approved nutrition facts information panel. Some companies also include the list of ingredients, which food labels must list in descending order by weight.

The software itself is enjoying a significant boom in business, says Layne Westover, vice president of marketing at ESHA Research, a Salem, Ore., company that sells one of the most commonly used programs, Genesis R&D.;

He says that when its software was launched in 1991, most food companies were more interested in the look, taste and profitability of their products, and nutrition labels were more an afterthought.

Now they realize consumers want that information, and profitability and appeal can depend on it, he says.

Chris Heinemann, chief marketing officer at San Francisco-based Savvy Wine Food, which manufactures gourmet nuts for pairing with wine, says nutrition analysis services have been invaluable for companies such as his, which lack the expertise to do the labeling themselves.

Having those labels, he says, isn’t just about meeting regulatory requirements. Having professional nutrition labeling lends credibilty to the products and helps get them into large retailers.

Despite the reluctance by some restaurants to include nutrition information on their menus, On The Menu’s Bush says offering consumers credible nutrition claims has helped many restuarants build customer loyalty.

Though most of their work is behind the scenes, nutrition analysis companies have begun reaching out directly to consumers. Bush and Spetnagel, for example, have a program called “Gluten Detectives” to help diners find gluten-free restaurant menus.

And Anita Jones-Mueller, whose San Diego-based Healthy Dining has seen business grow by a third in two years, partnered with the Centers for Disease Control and Prevention to launch www.healthydiningfinder.com, a free online service to help diners find healthy menu choices at restaurants around the country.

Which isn’t to say everyone wants or uses the nutrition information companies are rushing to supply.

“If you talk to people who own regular restaurants they will say often that when people go out to eat many of them don’t want that information in their faces,” says Jeanne Goldberg, a professor of nutrition science at Tufts’ Friedman School of Nutrition.

When it comes to food choices, nutrition may get a lot of attention, but it doesn’t always have much influence, she says.

“Taste is absolutely the No. 1 driver,” Goldberg says. “Cost and convenience tend to be Nos. 2 and 3. Health runs a solid fourth.”