Jun 16 2009

Heuristics and Weight Gain

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Comments: 13

I am often told by people who are frustrated at their inability to lose weight that they are not overeating. They insist that their caloric intake is low, which for most unsuccessful dieters is implausible (barring some medical condition). New research suggests that they may be sincere, but just suffering from a misleading heuristic.

A heuristic is a mental short cut – a down a dirty estimate or rule of thumb that we use subconsciously to quickly arrive at a conclusion that is mostly true. The presumed evolutionary advantage of heuristics is that they enable us to think and react quickly. A heuristic is a mental trade off of accuracy for speed.

An example of a common heuristic is the availability heuristic. Whenever we encounter a novel situation we reach for an available example from our own experience. We then assume that the available example is representative and will inform us about the novel situation.  When shopping for a dog, for example, and considering a doberman, one might observe – “my cousin had a doberman, and he was a mean and nasty dog.” This is the available example – and we will tend to make our decision based upon this one available example, without considering that it may not be representative.

Psychologists at the University of Pennsylvania have identified another heuristic that may contribute to unintended weight gain – unit bias. They found that people tend to ignore critical dimensions when considering the size of objects.

For example, they had subjects estimate the weight of different women based upon visual inspection, from either pictures or in person. The subjects were given information about the height of the women whose weight they were to guess – sometimes accurate, sometimes not. The researchers found that the subjects estimated weight based entirely on girth, and ignored height.

Likewise, the subjects were asked to estimate the amount of calories in a meal. The research suggests that the subjects did not consider portion size in their estimates. They considered only the “units” – let’s see, peas, chicken, and rice. This could mean that as portion sizes have risen in the US people have not taken this into consideration when estimating their caloric intake. They are still eating the same number of meals with the same number of components, given them the false sense that the caloric intake is the same.

Knowledge of heuristics is extremely important to critical thinking and skepticism. The more we understand about how the mind works, the more we will be able to avoid its pitfalls.

This research suggests that people should make a conscious effort to think about all relevant dimensions when estimating amounts. With regard to weight control – this means paying more attention to portions. It is already part of conventional wisdom that portion control is key to controlling caloric intake. This research supports that conclusion, and further explains why people seem to be so bad at estimating how many calories they intake.

13 responses so far

13 Responses to “Heuristics and Weight Gain”

  1. superdaveon 16 Jun 2009 at 9:01 am

    this is why I am a big fan of the NY legislation that fast food chains have to post calorie information on their menus. The calories in these foods is often (offen) counter intuitive. For example, the fish sandwich at Burger King has 100 more calories than the Whopper. Many fast food chain now consider a 16 ounce soda to be a small. Tis is two servings of beverage, but because it’s the small, it intuitively seems like it should be at least one serving, and maybe even less.

  2. jugaon 16 Jun 2009 at 11:26 am

    The implication of what you are saying is that if a hundred similar people eat the same meals and take the same exercise, they will weigh the same. That seems implausible from most people’s experience.

    Is your assertion based on empirical research or on a theoretical understanding of calorie intake?

  3. Steven Novellaon 16 Jun 2009 at 11:50 am

    juga – that is not the implication of what I am saying at all. This is a common misunderstanding though.

    You are comparing different people, I am saying that for an individual if they consume more calories without increasing their activity they will gain weight.

    Different people can have very different metabolisms, percentage of brown fat, hormonal profiles, etc. So you cannot compare person A to person B in terms of their caloric intake.

    You can, however, make statistical comparisons of large groups of people. If such comparisons are properly done, then metabolic differences should average out and it may be possible to pull out one variable – such as activity. You may be able to conclude, therefore, that people who walk more tend to have lower BMI.

    But what I am talking about is that if person A increases their portion size (perhaps without realizing it) while keeping their activity level constant, they will likely gain weight. And if they want to lose weight decreasing their portion size is likely to be effective.

    See the difference?

  4. RonaldB.on 16 Jun 2009 at 12:52 pm

    This blog is music to my ears. I myself lost about 1/3 of my own bodyweight in 4 years. I weighed 152 kg (335 pounds). I did not follow any diet. I managed this by ignoring all diets and went looking for advise with my doctor. He told me the same thing you describe in your blog. Minding my calori-intake the way you describe and exercising more, I lost 46kg (108 pounds). I will never gain this weight again, because my body now is used to the ammount of food I eat. I never stopped eating hamburgers, candy, chocolate and all the other wrong stuff next to all the good stuff. You don’t need a diet-guru, you just need to think and act to it. I think discipline might be the most important word in losing weight or stopping weight gain.

  5. Zelockaon 16 Jun 2009 at 3:39 pm

    “You may be able to conclude, therefore, that people who walk more tend to have lower BMI”

    But this would be an incorrect assessment based on perception of BMI. BMI is nothing more than weight / height. It would be perfectly reasonable for someone that walks to have more muscle mass then someone that does not. Since muscle weighs more, someone that walks could have a higher BMI then someone that does not for at least a certain period of time and maybe longer depending on the calories the muscle / exercise uses compared to the conversion of the excess on the person that does not walk. If you would have used body fat rather than then you would have removed this loophole.

    I would also generally take issue with more calories always equals more weight is a conclusion. There are a ridicules amount of variables involved in the human body and weight loss and gain. While likely that this statement will always be true, it would only be a noticeable factor at a certain scale depending on gender/ activity level / makeup / feeling of fullness / esc. From what I see the study didn’t even take these factors into account in the study. All they proved is that humans tend to think of items as units rather than as multiple collections of the same item together. This is not a new idea since we had a treat sized candy bar study related to this last year (I think) and I know I have seen this conclusion more than once before in earlier studies. I will see about locating it

  6. HHCon 16 Jun 2009 at 6:12 pm

    Researchers state that the width of the female models were focused on by subjects. I need a little more clarity of the research here. A female model can have width measurements at the bust, abdomen, and hips. The female bust contains 80-90% fat with the remainder of 10-20% muscle. That means a DD cup is overflowing with body fat! If the focus of the research was at the waist, we’re talking about a pretty pooch. If the focus was at the hips and thighs we are looking at a pear shape. Regardless, women should be aware that breast size reduces when fat reduction is aimed at in the diet. Proper proportions of foods can lead to a properly proportioned body.

  7. artfulDon 16 Jun 2009 at 6:51 pm

    “Proper proportions of foods can lead to a properly proportioned body.”

    Shore sounds lak one a them thar heuristics, don’t it?

  8. PhilBon 16 Jun 2009 at 7:23 pm

    Having used food logs as a tool for weight loss/gain, this sounds pretty accurate. With going to Burger King for lunch, a restaurant for dinner and drinks, if you total it all up it’s remarkably easy for a person to consume 2500 or more calories in a day. I’ve totalled up the calories from a night out at the bar and that alone can break a belt.

    There’s a corollary heuristic as well, the 2000 calorie diet. As you mentioned, caloric requirements can vary widely from individual to individual depending on base metabolism, exercise and other factors.

  9. HHCon 16 Jun 2009 at 9:16 pm

    We aren’t told what sex the college-age participants were in these university studies. I will assume that there was a mixture of male and female subjects. So by analogy, the same subjects will look at male models’ width when judging stimuli, but the same problem would be apparent with studies of men. They can have extremely large, flabby busts as well as women. The male paunch can extend past their thighs. The male rear torso can look like a wide padded table top. We could only guess which widths of the model were of interest to the college students.

  10. colli037on 17 Jun 2009 at 11:43 am

    The issues of calories vs weight is always difficult. Overweight patients burn fewer calories fidgeting (“sedentary” lifestyle) than thin patients. Morbidly obese patients move much less than thin patients. If you eat more calories than you burn, you will gain weight. If you eat 1000 Kcal/day, and spend all day in bed, burning only 800 Kcal/day you will gain weight.

    Active duty soldiers on field exercises (esp. infantry) can need as much as 4000 Kcal/day to keep their weight. Most back pain patients need less than 2000 Kcal to start losing weight unless they can exercise.

    It takes a huge amount of aerobic exercise to develop more


  11. Kitapsizon 19 Jun 2009 at 8:54 pm

    It is certainly amazing how poor the brain very often is with basic accounting; their are numerous studies done about this, with uniform results.

    I recently read “How We Decide”, by Jonah Lehrer and was amazed at the often times inappropriate models we use to make choices, so this really comes as no surprise after the book.

    Fixing the issue, might be a difficult tackle, no surprise there.

  12. FByrdon 23 Jun 2009 at 5:19 pm

    This rings true with me. I, personally, have lost 40 pounds by simply being more clinical with my food, as well as changing my lifestyle. Where I go to school, I have to walk at least 30 minutes per day, uphill both ways, to and from my dormitory to classes and between classes. Once I started this (moderate) routine, I noticed a slight weight drop, so I started to check my caloric intake and make sure that I measured everything as close as possible so that I wouldn’t fall victim to overestimation.

    I believe I saw somewhere a guide posted by the NIH that said people underestimate daily caloric intake by as much as 400-900 calories a day. It is a serious barrier to weight loss, along with our lifestyle and busy schedules not allowing people enough “time” to exercise.

  13. ConditionOfManon 28 Jun 2009 at 3:14 am

    You’re right Kitapsiz, our brain is very bad at accounting. There have been studies where a group was asked to estimate the total of 1*2*3*4*5*6*7*8*9 and another group to estimate 9*8*7*6*5*4*3*2*1. Our brains just calculate the first few numbers and spits out a guess. Of course the totals would be the same for each equation due to the commutative property, but with only a short time to guess, the first group gave a rather small number and the second group gave a larger one. They were both much lower than the actual total, which is 362,880. This can be attributed to the representativeness heuristic. The same heuristic might be to blame for weight gain from dieting where “I used to eat three meals a day, but only eat one now” but not accounting for an increase in calories for the one meal to the degree that they consume more calories than the aggregate of the three. They may also have less energy and therefore expend fewer calories than before as well.

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