"I had no idea the obesity crisis was a real crisis, but when you actually look at the economic consequences it's enormous," Thomas Schultz, a professor of psychology and computer science at the university, said from Montreal.
"If unchecked it will bankrupt the medical systems in even the richest countries, so it's an important problem."
Schultz and Peter Helfer, lead author of the study and a PhD student in psychology and neuroscience at McGill, compared four labelling systems.
They found that Percent Daily Value, the nutrition facts label on most food products in Canada and the United States, was the least usable.
A system called NuVal, which scores foods on a scale of one to 100, developed by Yale University professor David Katz, came out on top.
The Traffic Light system used in the U.K. let people make more nutritious choices but took more time to assess because the colours of several traffic lights have to be counted and compared.
The fourth type, a binary system that certifies some foods as nutritious but not others — similar to Canada Health Check — made for quick decisions but didn't increase nutritious choices, the researchers found.
"What our study shows is that a system like (NuVal) could be useful; something that simplifies nutrition information, resolves conflicts, is very easy and quick to use," Schultz said.
For their study, Schultz and Helfer recruited 192 participants from Canada and the U.S. and conducted an online experiment to measure people's ability to compare pairs of foods on nutrient levels — based on labels — and to estimate amounts of saturated fat, sugar, sodium, fibre and protein in the foods.
The %DV is "such a bad system that people will use advertising on the product instead — and advertising can be very deceptive," said Schultz.
"And the food companies have learned that they can charge more for products that have nutrition-sounding advertising on them. Like advertising low-fat, they can charge more for that and people are willing to pay it."
But registered dietitian Christy Brissette thinks a graph or stoplight system — requested by many consumers when Health Canada opened up discussions about improving food labels — helps people interpret nutrition at a glance, rather than oversimplifying it into a single number such as with NuVal.
"People like the idea of seeing this kind of stoplight where you get a red, or high, for something like salt and that might give you the red flag if you're watching salt in your diet," Brissette said.
The problem with a rating system is that it doesn't take into account that not everyone needs the same nutrients, she added.
The majority of the population needs to ingest more potassium, for example, and its content in a food would raise its score. But people with kidney disease or other conditions might need to limit the mineral.
"Based on the system (NuVal) uses, it would rate a yogurt that uses artificial sweetener as being more nutritious than a plain yogurt because the artificially sweetened one would be lower in total sugar," said Brissette, who works in the Ellicsr kitchen at Princess Margaret Hospital in Toronto.
"This is really missing the bigger picture of choosing more natural, less processed foods when it just assigns a number or tries to make this mathematical and puts all the nutritional information under one bucket."
Reading ingredients lists is key, she added.
"If there's all kinds of chemicals you can't pronounce it's not going to be a healthy choice and so this does ignore that aspect," Brissette said.
Health Canada is currently overhauling nutrition labels, taking into account such factors as suggested serving sizes being more consistent among similar foods and helping consumers determine how much sugar is in packaged foods. A series of public consultations on the proposals ran until September.
Schultz said their evidence indicates a simpler system than the %DV used now is a step in the right direction, though he lamented there is a tendency on labels to emphasize the negative characteristics associated with health, like salt, sugar and fat.
"I think the NuVal system or something like NuVal does better by also emphasizing the positive aspects of food, not just the negative aspects. So the more positive aspects that food has and the fewer negative aspects, the better it's going to be. It seems unfortunate that people are coming up with schemes that just emphasize the negative," he said.
"I suppose the problem with tobacco is the model for that. You just put these warning labels on it and maybe people will use it."
The study is published in the December issue of Annals of the New York Academy of Sciences.
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