Many Caught in ‘Dieter’s Paradox’

Individuals who view themselves as weight conscious are more likely to believe adding a healthy option to an otherwise indulgent meal lowers the total calorie count, according to new research from Northwestern University’s Kellogg School of Management.

“An important factor contributing to the obesity epidemic is the misguided belief about the relationship between a meal’s healthiness and its impact on weight gain. People intuitively believe that eating healthy foods in addition to unhealthy ones can decrease a meal’s calorie count," said Alexander Chernev, study author and associate professor of marketing at the Kellogg School.

As part of the study, 934 participants from a nationwide online research panel were asked to estimate the caloric content of several meals. Some were shown a series of relatively unhealthy meals, and others were shown the same meals combined with a healthy option. For example, some of the participants were shown a bowl of chili with cheese, whereas the others were shown the same bowl of chili paired with a small green side salad. The other food pairs included a cheeseburger, which for some of the participants was paired with three celery sticks; a bacon-and-cheese waffle sandwich (paired with a small organic apple); and a meatball pepperoni cheesesteak (paired with a celery-and-carrot side dish).

Those who viewed the chili alone rated it as averaging 699 calories. Those who were shown the chili combined with the green salad estimated the meal to have only 656 calories. Adding a green salad to the bowl of chili lowered the perceived caloric content of the entire meal by 43 calories—as if the green salad had negative calories. This negative-calorie illusion was observed with all four meals tested, indicating the prevalence of the belief that one can consume fewer calories simply by adding a healthy item to a meal.

To combat the “dieter’s paradox," Chernev recommends that the focus of current public policy campaigns shift away from the stereotypes associated with “good" and “bad" foods. When product ads and public policy communications stereotype foods into virtues and vices, they tend to shift peoples’ attention away from the quantity of food consumed. He said this neglect of quantity might end up implicitly promoting the illusion of negative calories.

“The bottom line here is that motivating people to lose weight without educating them on how to monitor their caloric intake might not be enough to combat obesity. As the dieter’s paradox shows, motivation without knowledge can be counterproductive," he said. “Promoting the consumption of healthy foods without providing a complete picture of the factors influencing weight gain might paradoxically facilitate caloric overconsumption, leading to weight gain rather than weight loss."