The Dieters Paradox – Research Review

Chernev A.  The Dieters Paradox.  Journal of Consumer Psychology.  (2001) 21: 178-183.

Despite the vast public policy efforts to promote the consumption of healthy foods and the public’s growing concern with weight management, the proportion of overweight individuals continues to increase. An important factor contributing to this obesity trend is the misguided belief about the relationship between a meal’s healthiness and its impact on weight gain, whereby people erroneously believe that eating healthy foods in addition to unhealthy ones can decrease a meal’s calorie count. This research documents this misperception, showing that it is stronger among individuals most concerned with managing their weight—a striking result given that these individuals are more motivated to monitor their calorie intake. This finding has important public policy implications, suggesting that in addition to encouraging the adoption of a healthier lifestyle among overweight individuals, promoting the consumption of healthy foods might end up facilitating calorie overconsumption, leading to weight gain rather than weight loss.



In introducing today’s paper, I am reminded of an old joke/quip to the effect that “All that separates man from the animals is our ability to rationalize.”   I’d add “And accessorize” but that’s neither here nor there.  But the reality is that humans are able to do a wide variety of mental gymnastics in how they approach life.  Effectively, we appear to be slave to what psychologists call cognitive biases, ways in which we think about the present, past, future or ourselves that often lead us to make some fascinatingly bad choices.  This is a topic that many recent books has discussed in a variety of contexts.

And while I don’t know if I can say that it occurs to a greater degree in terms of eating and health behaviors, there is no doubt that people often engage in some exceedingly interesting mental gymnastics when it comes to those topics.  Some of this is conscious but much of it can be chalked up to either unconscious behaviors, misunderstandings (or a lack of information/education) or mishearing/misinterpreting the message.   And these types of things, as much as anything else, often derail many people’s attempts to eat healthy, lose weight or simply avoid weight gain.

In the realm of exercise for example, many people grossly overestimate the actual caloric expenditure from activity, as I discussed in Normal Weight Men and Women Overestimate Energy Expenditure – Research Review, and this leads them to either expect far more of an impact on weight loss than is realistic or to eat more calories than they actually need based on the assumption that they burned it off during activity.

In the arena of eating, this issue can show up in a myriad ways.  A classic example of a misunderstanding/garbling of the message occurred back in the 80’s during the low-fat eating craze.   While it’s hard to say where the blame lies, the general public sort of got the message that so long as they kept fat intake low, nothing else really mattered.  Caloric intake and portions went out the window.

Food companies capitalized on this by rushing plenty of energy dense, high-calorie (but low-fat) foods to market and it all went wrong.  Studies routinely found that people ate more food when it was labelled ‘low-fat’ compared to one that was labelled as being higher in fat.  Either consciously or unconsciously, they gave themselves permission to eat more of it.  And often ended up consuming more calories than they would have otherwise.

Another example deals with artificial sweeteners where you often see a pattern where artificial sweetener (or diet soda) intake is associated with weight gain (or a lack of weight loss).  And while there is some speculation that artificial sweeteners do some odd things in the brain in terms of driving appetite, it’s probably more related to people rationalizing that they can eat more of something else because they are getting less calories by choosing diet soda or using artificial sweeteners.   That is, they figure that since they are ‘saving so many calories’ by making one choice, they end up compensating (or more than compensating) by choosing something unhealthy.  Call this the skim milk and chocolate cake or Diet Coke and cheeseburger approach to eating.

I’d note before continuing that this much of the above rationalizing tends to be more for people who are only paying somewhat ‘superficial’ attention to ‘eating well’ (or some other fairly abstract goal).  That is, the type of thing I’m going to talk about doesn’t generally occur among folks who are diet obsessed and track macros or calories or what have you.  Rather it’s for folks who, while they may say that they are concerned with their diet or body weight or body fat, are focusing on the wrong things (a topic I addressed in more detail in Fundamental Principles vs. Minor Details).

Finally type of behavior seems to occur more prevalently in people who tend to divide foods into ‘good’ and ‘bad’ categories (a category that many popular diets and dietary approaches tend to promote).  ‘Good’ foods become equated with healthy and, altogether too often, can be eaten without consequence (i.e. weight gain).  Researchers call this the ‘health halo’ by which supposed ‘healthy foods’ have a halo of invincibility around them  In the same vein ‘bad’ foods are equated with being unhealthy and this categories are not only absolute but cause us to do some of those strange mental gymnastics when it comes to how we approach our food intake.

You can find examples of this all over the place where people assume that ‘healthy/good’ foods can be eaten in uncontrolled amounts whereas the tiniest amount of ‘unhealthy/bad foods’ mean that the diet has failed, the dieter is immoral and weak, and health will simply be destroyed (this is seen at the greatest extreme in a psychological condition called orthorexia whereby people see food as a moral choice judging not only themselves but others by the foods that they choose to eat).  You can see some good examples of this in the comments section of Straight Talk About High-Fructose Corn Syrup: What it is and What it Ain’t. – Research Review.

Which basically segues into today’s paper which examines a behavior pattern that is often seen whereby folks tend to get fixated (or perhaps ‘blinded’ is a better word) by the concept of ‘healthy’ foods and end up missing the forest for the trees when it comes to their food and caloric intake.   There is also evidence that people who are (or at least state that they are) more ‘weight conscious’ are even more prone to make these kinds of mis-estimations which was a secondary aim of the study.


The Paper

The study recruited 934 people, of whom the majority (74.2%) were female aged anywhere from under 20 to over 50.  Subjects were then shown 4 meals which either consisted of ‘unhealthy’ foods or those same unhealthy foods coupled with a healthy option.  The four meals, with the healthy addition shown in parentheses, were a hamburger (three celery sticks), bacon and cheese waffle sandwich (small organic apple), chili with beef (small salad without dressing) and meatball pepperoni cheesesteak (celery/carrot side dish).   So, for example, subjects were either shown a bacon and cheese waffle sandwich (which sounds amazing in so many ways) either by itself or side by side with a small organic apple.

Half the subjects were shown the unhealthy choice alone and the other half were shown the combination of the unhealthy choice with it’s healthy add-on and they were asked to estimate the caloric value of the meals.  I’d mention that this design is problematic because it’s not comparing how a given individual might rank each of the two meals; rather it’s comparing the average estimate of the caloric value of the different meals between people.  All subjects were also asked to rate how concerned they were with managing their weight on a scale of 1-5 (with 5 being extremely concerned).

The study generated a total of 2750 total observations of the different meals and, on average, subjects estimated that the unhealthy meal alone contained 691 calories.  Now, logically it’s obvious that a food consisting of an unhealthy item PLUS a healthy item would have to have more calories than the unhealthy item alone.   Clearly two foods can’t have less calories than either food alone.

Yet, on average, subjects estimated the unhealthy plus healthy choice as having only 648 calories.  I’d mention that as a third part of the study, a separate group was asked if they believed that the healthy foods contained negative calories and this was not the case.  So it doesn’t appear to have been the case where subjects figured that the healthy addition was literally ‘reducing’ the caloric value of the food by containing negative calories.  Rather, the ‘health halo’ effect caused people to systematically underestimate the caloric value of the combination of an unhealthy and healthy food.

But it gets even odder.  When the estimates were ranked by how folks reported their concern with managing their weight, the values changed even more.  The most ‘weight conscious’ subjects estimated the unhealthy meal as containing 711 calories while the combination of the unhealthy and healthy choice was only 615 calories. In contrast, the non-weight conscious individuals estimates were only 684 for the unhealthy choice versus 658 for the combination and there was a direct relationship between how weight conscious the subjects were and their mis-estimate of the different meals.


My Comments

I really don’t have a ton to add to the above, the paper goes into lot of discussion that I’ll spare you here since it’s a lot of detailed examination of the possible underlying mechanisms behind these types of odd cognitive biases.   One point that was made was that while one might expect more motivated/involved people to have less problems with these types of conceptual biases, this research found the opposite.  To whit:

The negative calorie bias is more pronounced for more involved/motivated individuals. Thus when evaluating vice/virtue combinations, greater motivation does not necessarily result in greater accuracy but instead can lead to more biased judgments.

I would add that I think really has more to do with what I mentioned in the background above, the issue isn’t with dietary motivation per se but rather with how people often conceptualize the process.  By focusing on things like good/bad foods, clean vs. unclean eating, meal frequency exclusively or organic vs. non, people lose sight of the issue of portions and calories which are what really matter when it comes down to it. They rely on estimates which are oh so often off.  And which appear to be colored heavily by the cognitive biases that many humans are so prone towards.

Make no mistake, certain types of eating patterns often automatically get people to reduce their intake, often by the outright removal of a so-called ‘bad’ food.  What is defined as good or bad depends on the diet in question and certainly these types of good/bad approaches to dieting can work in at least the short-term (and sometimes longer than that).  The problem is when people start focusing on the goodness/badness of the foods they are eating to the exclusion of everything else.  That’s when it often goes wrong; this is not helped by many dietary approaches telling folks that calories/portions don’t count and that focusing only on the aforementioned ‘good/healthy’ foods is all that matters.

In this vein, the paper’s author notes that:

In particular, the negative calorie illusion has been shown to be less pronounced when individuals pay attention to the quantity of the combined items, instead of focusing solely on the healthy/unhealthy aspects of the items.

In a related vein, the author points out that:

Another public issue raised by this research concerns the viability of promoting the very notion of stereotyping foods into vices and virtues.  Despite it’s intuitive appeal as a decision heuristic to simplify choice, vice/virtue categorizations focuses consumers’ attention only on one aspect of the meal [my note: whether the food is a ‘vice’ or a ‘virtue’] and ignores other important aspects such as its overall quantity.

And I really think that that’s the big take home message of this rather odd paper: people often get so fixated and focused on the wrong things that they end up hamstringing their own attempts to reach their goals.  Because while it’s all well and good to focus on healthy/unhealthy, good/bad, clean/unclean or whatever, at the end of the day quantities always count.  When people lose sight of that and focus on the wrong aspects exclusively, they often end up hurting their own progress.  This paper just points out one way that this happens.

I’ll finish by pointing interested readers to a book by the paper’s author titled  The Dieter’s Paradox: Why Dieting Makes Us Fat that addresses not only this research but a great deal of other research looking at similar issues.  How humans tend to categorize foods into good and bad and how it can lead them to make a lot of really weird assumptions about what they are actually eating.  It was a pretty fascinating read and shows how many different ways we can end up screwing our own progress by relying on our (often incorrect) intuition, primarily by focusing on the wrong factors that are relevant to what we are eating.



15 thoughts on “The Dieters Paradox – Research Review

  1. I only wish I had read this 15 years ago before my joyrides with vegetarianism, veganism, Taubes-induced low-carb zealotry, and finally paleo (yes, I’m a sucker for dietary dogma). My newest attitude is that of dietary minimalism where I try to adopt the fewest attitudes & beliefs towards food and to the best of my ability shed those beliefs already knocking around in my head (might take awhile). This approach reminds me of a book I read in high school called Zen Mind, Beginner’s Mind. “The mind of the beginner is empty, free of the habits of the expert, ready to accept, to doubt, and open to all the possibilities.”

  2. Interesting paper, and the review is some of your best writing. Sadly, the people I know who most need to read this (obese, endlessly talking about what is and isn’t ‘healthy’) would either miss the point or take offense if I showed it to them.

  3. Maybe if you americans stopped classifying food such as pizza as a “vegetable”, you wouldnt have this big obesity epidemic, LOL.

  4. This reminds me of the time that my mother took us out to McDonald’s, and in the vein of healthiness went with a Happy Meal instead of a full value meal. She’s been struggling with her weight her entire life, but she focuses on minor details instead of the actual calories in vs. calories out broad-scope approach to dieting. For example- she’ll skip breakfast, but insist on devouring dark chocolate for the antioxidants. “Dieting” to her is about only paying attention to the advice that compliments her existing lifestyle.

    Which is why she washed that Happy Meal down with a SlimFast.

  5. Great post Lyle, one question:

    For some people, do you think it may be easier to simply eat as much of one food (like vegetables) as they want, since it’s almost impossible to eat enough to create a calorie surplus? Even if they could, it’s likely something like broccoli probably wouldn’t even digest in monumental quantities. Obviously calories still matter, but do you think it’s ever effective to basically restrict your options to low calorie foods instead of deliberately counting?

    Thanks again,


  6. The joke/quip is actually Aristotle’s definition of man as a ‘a rational animal’ which Nietzsche had a big problem with. Your line about people able to make ‘fascinatingly bad choices” is great!

  7. I resemble that remark. In my mind, the apple/salad thing is not about deleting calories as it is about changing proportion – I’ll have a smaller bacon cheeseburger waffle if I eat the apple first, with, or after. Whether I’m going to make a smaller one, not go back for seconds, or am less likely to eat another meal soon, especially at home. obviously in a restaurant the apple is canceling out the fries I would have eaten off of someone else’s plate.

    Splenda, well, may be more silly, but the idea is that I use splenda every day and I order the chocolate cake once a week. The occasional sugar-high instead of the daily one.

    DId they include the long-term effects of such rationalizations? Because I think they work for me; when I include more healthy foods or activities, they nudge out the more unhealthy ones; either my weight goes down or stops going up.

  8. Hey Lyle, great article.

    A question if you don’t mind slightly off topic but you mention “Another example deals with artificial sweeteners where you often see a pattern where artificial sweetener (or diet soda) intake is associated with weight gain (or a lack of weight loss” – can you point me in the direction of some reading on this? Not the cheeseburger & diet coke aspect but just if there’s any link between drinking too much Pepsi Max and a lack of weight loss when I’m pretty strict elsewhere in my diet. I’m currently using the Leangains IF regime but seem to have stalled for quite a bit..

    Cheers for your time

  9. Great read. Concerning the dichotomy in foods, I think religion has contributed a lot to this. This is why I think teaching fasting in kids teaches them to think with a bipolar manner on food choices.

  10. Consider all the preaching about how adding “healthy foods”- i.e., foods having a lot of fiber – acts to decrease blood sugar elevation from those high glycemic “unhealthy foods”. People have also been taught that soluble fiber (such as is in oats) will decrease reabsorption of cholesterol and presumably other fats (the fiber breaks up the micelles necessary for absorption of fats). I don’t think people are being unreasonable at all; they’re just acting on the messages they’ve absorbed about how fiber counteracts the “bad” effects of some foods. The fact that this may not be actually true isn’t their fault.

  11. Great article. I think it’s so true in many respects. I’ve watched many friends rationalize the diet coke and cheeseburger diet. It doesn’t work. What does work is the side salad with a healthy meal lifestyle. I noticed that in the study there was no healthy meal option for the participants to estimate. I find that a flaw in the study. Personally, given almost any of those meals, healthy option or not I’d estimate about 1000 calories. That’s mainly b/c I don’t like the options their offering and I’m biased against them. (Tastewise, here.) I would be interested in seeing what that kind of addition the study woudl do to it.

    I agree also with RG. The healthy option does reduce the calories of the rest of it by reducing how much the person would eat-if that person thinks that way. But I’m thinking that wasn’t the question asked in the study. But it’s the way we tend to think. Think the best of ourselves, regardless of whether we would follow through on it.

    I do think it would be an interesting undertaking to educate the broader public to what is going on in here. As Cynthia said, many simply do not know. What would you recommend as a starting point for this educational undertaking?

  12. Hi Mr McDonaald, haven’t heard from you for a while here or on the Charlie Francis site. I hope everything is OK. In the past you mentioned that alcohol has a specific effect on the system and you mentioned you would address the subject in the furure. I would appreciate it if you could comment on the subject in a future newsletter.

    Thank you for sharing your vast knowledge and again hoping that you are doing well.


  13. Excellent article review Lyle. Cognitive bias is a fascinating aspect of the human condition.Thanks for highlighting this as it pertains to food attitudes and choices.

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