A Dieting Conundrum
Skip to content
Marketing Jan 1, 2012

A Dieting Conundrum

Why dieters underestimate calorie counts of meals

Based on the research of

Alexander Chernev

In the effort to combat the burgeoning problem of obesity, authorities such as the United States Centers for Disease Control and Prevention and the World Health Organization promote the benefits of healthy eating plans that include plenty of fruits and vegetables. Individuals concerned with their weight often internalize that message. But they frequently do so in an irrational way. According to research by Alexander Chernev, an associate professor of marketing at the Kellogg School of Management, many think that adding a “healthy” option, such as a side dish of celery and carrots, to a high-calorie meal such as a cheesesteak somehow reduces the meal’s overall calorie content.

Chernev’s research also gives the tale an added twist: the more serious that individuals are about dieting, he finds, the more likely they are to fall for this “side salad illusion.” “People often behave in a way that is illogical and ultimately counterproductive to their goals,” Chernev says. “We’ve shown that people on a diet are more likely to underestimate the calorie count of combinations of healthy and unhealthy meals.”

The Dieter’s Paradox

Information about the “dieter’s paradox,” as Chernev calls it, emerged from a nationwide study in which more than 1,000 respondents were asked to estimate the calorie count of a variety of meals. About half the respondents saw a series of unhealthy meals: a hamburger, a bacon and cheese waffle sandwich, chili with beef, and a meatball pepperoni cheesesteak. The rest saw these same unhealthy meals accompanied by a healthy item—a few celery sticks, a small organic apple, a small salad without dressing, and a side dish of celery and carrots, respectively.

Respondents who saw only the unhealthy meals estimated that they contained 691 calories on average. But those who saw those same meals accompanied by the healthy items assessed the average calorie count at just 648. For example, participants shown a bowl of chili rated it as averaging 699 calories; however, participants who viewed the same bowl of chili combined with a green side salad rated it as having only 656 calories. In every case the addition of the healthy food item led to the erroneous perception that the number of calories had decreased.

After the participants evaluated the calories in these meals, they were asked to indicate the extent to which they were concerned with managing their weight. Astonishingly, the data showed that the most weight-conscious individuals believed most strongly in the apparent ability of a healthy option to reduce the calorie content of an unhealthy meal. Those more concerned with their weight rated the unhealthy item paired with a healthy one as having 615 calories—96 calories less than dieters who rated the unhealthy item alone. People less concerned with their weight were not as susceptible to the side salad illusion. They estimated the unhealthy–healthy combination as having only 26 calories less than the unhealthy item alone (Figure 1).

Chernev2011_Fig1.gifFigure 1. Weight-conscious individuals are more likely to believe that adding a healthy option to an unhealthy meal decreases a meal’s calorie content.

“The fact that those most concerned with their weight are also more likely to underestimate the calorie content of a meal is counterintuitive,” Chernev says. “It also means that they will be more likely to overconsume and consequently more likely to gain weight.”

A World of Vices and Virtues

What could cause this apparently illogical behavior? Maybe dieters really believe that healthy food items have negative calories—perhaps because the energy needed to digest them exceeds their calorie content. To test that possibility, researchers asked a separate group of respondents to estimate the caloric value of the healthy foods in the main study. Not a single participant believed the healthy items had negative calories.

“The data show that the dieter’s paradox is not caused by people’s beliefs that healthy items like broccoli have negative calories,” Chernev points out. Instead, he argues, the dieter’s paradox stems from a fundamental flaw in the way we think about food healthiness and its impact on our weight.

“This black-and-white view of foods is the key driver of people’s tendency to underestimate the calorie content of meals combining virtues and vices.”

“People think of food in terms of vice and virtue—healthy and unhealthy,” Chernev explains. “The easiest way to diet is to categorize into good and bad; you aim to minimize the bad and maximize the good. The more you want to lose weight, the more likely you are to categorize foods into vices and virtues. So when we add something healthy to an unhealthy food, we think it makes the entire meal healthier. And because we often confuse a meal’s healthiness with its calorie content, we think that healthier meals are also more diet-friendly. Hence, we assume that the vice/virtue combination is not only healthier but also has fewer calories than the vice alone.” In other words, he adds, “virtue makes the vice seem less ‘vicey.’ ”

Those most concerned with managing their weight are also more susceptible to these errors in judgment, Chernev says. Because the side salad illusion stems from our tendency to stereotype foods into vices and virtues, it tends to be more prevalent among individuals most likely to invoke such stereotypical thinking. Many dieters fall into that category.

“This is because most nutritional guidelines, as well as many diets, focus on promoting the consumption of certain food groups while advocating reduced consumption, or even avoidance, of others,” Chernev says. “And although particular guidelines and diets vary in the type of foods and nutrients they consider acceptable or unacceptable, most share the underlying principle of categorizing foods into virtues and vices. This black-and-white view of foods is the key driver of people’s tendency to underestimate the calorie content of meals combining virtues and vices.”

A Balancing Act Beyond Dieting

This balancing act is not unique to dieting. “We show the same effect with prices. When you add something inexpensive to an expensive item, people often assign less value to the combination than to the expensive item alone,” Chernev says. “The same thing is likely to happen with the duration of time, when you combine short intervals with long intervals.”

Chernev, who reports that “I’m not on a diet, but I add healthy options to my meals,” is the author of the book The Dieter’s Paradox: Why Dieting Makes Us Fat. In it he argues that trying harder to achieve such goals as managing our weight does not necessarily make us smarter when we choose the means to pursue those goals. “As evidenced by dieters’ tendency to underestimate the calorie content of their meals by combining virtue and vice options,” he says, “greater motivation often leads to outcomes that are counterproductive to our goals.”

Similar thinking applies to public policymakers. “Providing healthy options is not a solution; it’s part of a solution,” Chernev asserts. “What you really need to provide people with is not just information, but knowledge on how to make decisions.” Thus, any strategy to improve calorie counts should focus not on the types of food we eat, whether virtuous or vice-ridden, but on the quantity consumed. “The goal should be to cut the burger in half,” Chernev advises, “not add a salad to it.”

Related reading on Kellogg Insight

Be Good, Get Mad: Exerting self-control makes people more inclined to anger

Are Restaurants Really Supersizing America? Restricting restaurant meals may not trim Americans’ expanding waistlines

About the Writer
Peter Gwynne is a freelance writer based in Sandwich, Massachusetts
About the Research

Chernev, Alexander. 2011. “The Dieter’s Paradox.” Journal of Consumer Psychology. 21(2): 178-183.

Read the original

Most Popular This Week
  1. Sitting Near a High-Performer Can Make You Better at Your Job
    “Spillover” from certain coworkers can boost our productivity—or jeopardize our employment.
    The spillover effect in offices impacts workers in close physical proximity.
  2. Will AI Kill Human Creativity?
    What Fake Drake tells us about what’s ahead.
    Rockstars await a job interview.
  3. Podcast: How to Discuss Poor Performance with Your Employee
    Giving negative feedback is not easy, but such critiques can be meaningful for both parties if you use the right roadmap. Get advice on this episode of The Insightful Leader.
  4. 2 Factors Will Determine How Much AI Transforms Our Economy
    They’ll also dictate how workers stand to fare.
    robot waiter serves couple in restaurant
  5. How Are Black–White Biracial People Perceived in Terms of Race?
    Understanding the answer—and why black and white Americans may percieve biracial people differently—is increasingly important in a multiracial society.
    How are biracial people perceived in terms of race
  6. The Psychological Factor That Helps Shape Our Moral Decision-Making
    We all have a preferred motivation style. When that aligns with how we’re approaching a specific goal, it can impact how ethical we are in sticky situations.
    a person puts donuts into a bag next to a sign that reads "limit one"
  7. Will AI Eventually Replace Doctors?
    Maybe not entirely. But the doctor–patient relationship is likely to change dramatically.
    doctors offices in small nodules
  8. What’s at Stake in the Debt-Ceiling Standoff?
    Defaulting would be an unmitigated disaster, quickly felt by ordinary Americans.
    two groups of politicians negotiate while dangling upside down from the ceiling of a room
  9. How to Manage a Disengaged Employee—and Get Them Excited about Work Again
    Don’t give up on checked-out team members. Try these strategies instead.
    CEO cheering on team with pom-poms
  10. One Key to a Happy Marriage? A Joint Bank Account.
    Merging finances helps newlyweds align their financial goals and avoid scorekeeping.
    married couple standing at bank teller's window
  11. Why Do Some People Succeed after Failing, While Others Continue to Flounder?
    A new study dispels some of the mystery behind success after failure.
    Scientists build a staircase from paper
  12. 5 Tips for Growing as a Leader without Burning Yourself Out
    A leadership coach and former CEO on how to take a holistic approach to your career.
    father picking up kids from school
  13. Which Form of Government Is Best?
    Democracies may not outlast dictatorships, but they adapt better.
    Is democracy the best form of government?
  14. Daughters’ Math Scores Suffer When They Grow Up in a Family That’s Biased Towards Sons
    Parents, your children are taking their cues about gender roles from you.
    Parents' belief in traditional gender roles can affect daughters' math performance.
  15. Take 5: Research-Backed Tips for Scheduling Your Day
    Kellogg faculty offer ideas for working smarter and not harder.
    A to-do list with easy and hard tasks
  16. What Went Wrong at AIG?
    Unpacking the insurance giant's collapse during the 2008 financial crisis.
    What went wrong during the AIG financial crisis?
  17. Leave My Brand Alone
    What happens when the brands we favor come under attack?
  18. The Second-Mover Advantage
    A primer on how late-entering companies can compete with pioneers.
  19. Take 5: Yikes! When Unintended Consequences Strike
    Good intentions don’t always mean good results. Here’s why humility, and a lot of monitoring, are so important when making big changes.
    People pass an e-cigarette billboard
Add Insight to your inbox.
More in Marketing