People often don't know how many calories they're eating, how many they burn off, or what they need, say doctors who are calling for prominent calorie labels at the point of sale.
The Canadian Obesity Network, a group of obesity experts, showed people examples of foods and asked them to guess how many calories the items contained.
"A lot of Canadians were quite off the mark," said Dr. Arya Sharma, chair in obesity research and management at the University of Alberta in Edmonton.
"When we showed people food labels and asked them to calculate how many calories they'd be getting if they consumed say a can of soup, very few Canadians were able to figure out that number."
Sharma is concerned about the consequences of caloric illiteracy considering two-thirds of Canadians are carrying extra pounds and a quarter of adults are considered to be medically obese, according to Statistics Canada.
"Ultimately calories are the currency of weight management," Sharma said. "If you don't know how many calories you're eating, you don't know what your body's doing with the calories, you don't know where the calories are going. That's like trying to manage your bank account without knowing how much money you make or how much money things cost."
The average woman needs to take in about 2,000 calories a day and the average man 2,400, Sharma said.
A single chicken wing contains about 100 calories, which would take a 20-minute bike ride or 1½-kilometre run to burn off, he added.
At the University of Waterloo, David Hammond found people consumed 11 per cent fewer calories when nutrition information was posted on restaurant menus compared with a control group, a difference of about 100 calories. An earlier U.S. study found the same result.
Hammond agreed that many people don't know their recommended daily intake of calories, but they can compare items, such as 210 calories for a small muffin versus 240 calories in a large muffin.
Gaining that relative sense of calories when making purchasing decisions helps make the information sink in and drives smarter choices, he said.
Another option is to use a traffic light pattern with calories in green, amber and red, the way pre-packaged foods are labeled in UK grocery stores.
"It's very difficult if not impossible to guess how many calories are in a meal, even trained dieticians can't do that," said Hammond. "The best way of giving that information to people is on the menu at the time they're making their food decisions."
Consumers may assume that a salad at a fast food restaurant is going to have fewer calories than a burger but that is not always the case, he said.
Many large restaurant chains now voluntarily provide nutrition information but they often put it in places that are difficult for consumers to find, such as on their websites and on posters away from the check outs, said Bill Jeffrey, national coordinator for the Centre for Science in the Public Interest, which is lobbying governments to make restaurants post nutrition information on their menus.
In the U.S., federal regulation will soon require calorie counts to be reported beside standard menu items at large chain restaurants.
In Canada, voluntary measures have been in place for several years, but Jeffrey called them "largely ineffective."
Last month, McDonald's in the U.S. announced it will unveil menu board labels in American restaurants in advance of the U.S. federal regulations.
"With regard to nutrition information in restaurants the conversation has progressed differently in Canada than it has in the U.S.," McDonald's Canada said in a statement at the time.
"McDonald's Canada is actively working with all levels of government, NGOs and industry stakeholders to develop an appropriate 'Made-in-Canada' solution to displaying comprehensive nutrition information that is easily accessible to customers prior to purchase."
Sharma cautioned he doesn't want people to obsessively count calories, but to have an idea of how many calories are in the foods when deciding what to eat.