Many diners opting for heart-healthy main meals still tend to overindulge, opting for rich side dishes, high-calorie drinks and heavy desserts, according to a new study published in the October issue of the Journal of Consumer Research.

Lead author Pierre Chandon, a marketing professor at France's INSEAD business school, says consumers are also more likely to underestimate calorie counts at restaurants that claim to be healthy such as the sandwich shop Subway, over restaurants like McDonald's.

'More generally, we need to think about food not just qualitatively — as in "good food-bad food" — but also quantitatively as in "how many calories are in this meal?"'—Pierre Chandon, researcher

The tendency to miscalculate calories along with the inclination to indulge in side dishes has helped create an obesity paradox. Healthy foods have become more popular while waistlines continue to swell, the study says.

"We find that consumers chose beverages, side-dishes, and desserts containing up to 131 per cent more calories when the main course was positioned as "healthy" compared to when it was not, even though the "healthy" main course already contained 50 per cent more calories than the "unhealthy" one," the study said.

Researchers conducted a total of four studies, asking consumers to estimate calorie content at McDonald's and Subway restaurants. The study found that consumers estimated Subway sandwiches contained fewer calories than McDonald's sandwiches, even when both sandwiches had the same number of calories.

Researchers say despite the growing popularity of healthy foods, obesity rates are still growing.
(CBC)

"The results of four studies show that consumers estimate that familiar sandwiches and burgers contain up to 35 per cent fewer calories when they come from restaurants claiming to be healthy, such as Subway, than when they come from restaurants not making this claim, such as McDonald's," the study said.

Participants consumed 56% more calories at Subway over McDonald's

In one experiment, 23 students were given a coupon for a Big Mac sandwich, which has 600 calories. Another 23 students were given a coupon for a Subway 12-inch Italian sandwich, which contains 900 calories. Students were also offered the option of supplementing their meal with a fountain drink and cookies and were then asked to calculate their meal's calorie content.

"Compared to those who had received a Big Mac coupon, participants who received the Subway coupon were less likely to order a diet soda, more likely to upgrade to a larger drink, and more likely to order cookies," the study said.

"Because the Subway sandwich also contained more calories than the McDonald's sandwich, participants ended up with a meal containing 56 per cent more calories in the Subway coupon condition than in the McDonald's coupon condition."

The authors noted the experiments also demonstrated that encouraging consumers to consider health claims critically helps to counteract the "obesity paradox."

"More generally, we need to think about food not just qualitatively — as in "good food-bad food" — but also quantitatively as in 'how many calories are in this meal?'" Chandon said in a release.