TORONTO - Canada's restaurants are doing their patrons a grave disservice by keeping nutritional facts off their menus, an Ottawa-based advocacy group suggested Tuesday.

The Centre for Science in the Public Interest said all levels of government must step in and make it mandatory to share the sort of dietary details that eateries so often keep under wraps.

A basic breakdown of calorie totals and sodium values, the centre argued, could go a long way towards stemming the rising tide of obesity in the country.

The centre's findings are outlined in "Writing on the Wall," a 90-page report analysing the impact that restaurants have on public health.

CSPI national co-ordinator Bill Jeffery said restaurant diners should have access to the sort of fundamental nutrition facts legally required to appear on all supermarket food packaging.

"Who would settle for seeing nutrition information in grocery stores in the manager's office or stacked up by the cash register?" Jeffery said in a telephone interview from Ottawa.

"It's just not acceptable. You need the information readily apparent at the point where you're making the decision, and having to jump through hoops to get that information just means that fewer people are going to use it."

The CSPI report assessed basic nutrition facts voluntarily compiled by more than 30 of the country's major chains, including Burger King, Casey's, Tim Hortons and East Side Mario's.

Many menu offerings contain two and three times the recommended daily calorie and sodium quantities an adult should ingest, with some dishes having up to two days worth of sodium in one serving.

The report said a fifth of Canadians' weekly food intake comes from restaurant meals, suggesting they play a significant role in rising incidents of hypertension and other obesity-related conditions.

Jeffery said much of this nutritional information is available to customers, but only if they actively seek it out.

Requesting nutritional brochures or researching meal options online ahead of time is impractical, he argued, suggesting that restaurants disclose a calorie total next to all items and add a high-sodium flag where appropriate.

A notice at the bottom of the menu stating the daily target of 2,000 calories and 1,500 milligrams of sodium would help diners put their choices in context, he said.

"Even trained dieticians are terrible at estimating the calorie counts and sodium levels for restaurant foods," Jeffery said. "This is the kind of thing where you really need objective information from the company that makes the product."

Joyce Reynolds of the Canadian Restaurant and Foodservices Association agreed a national framework for calorie disclosure would be a valuable service to patrons.

Unlike Jeffery, however, she believes menus are the wrong medium through which to communicate such information.

Customers want to consider many factors beyond calories and sodium when making their choices, she said, adding that menus don't offer enough space to properly display the necessary values.

"There's other organizations saying it should be trans-fats, and others are saying it should be allergins," she said. "There's no end to the number of pieces of information that would be a nice-to-have on the menu, but it's not possible."

Reynolds said the association is in talks with the federal government to devise a national framework for nutritional disclosure in restaurants.

Mobile apps may offer patrons a convenient way to research their food choices in the years ahead, she said.

Jeffery said the onus is on governments to set food disclosure rules, since eateries are loath to make such information accessible for fear of losing business.

"Restaurants recognize if people see how high the sodium levels and calorie levels are in their foods, they're going to expect that those foods be reformulated to suit their expectations about healthfulness," he said.

"It may be that some restaurant patrons decide that it's better for them to just make food at home."