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The Mathematician’s Obesity Fallacy

The views expressed are those of the author and are not necessarily those of Scientific American.

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obesity man park benchAs I write, this interview with mathematician Carson C. Chow is the number-one most-emailed story on the New York Times Web site. Chow, a researcher at the National Institute of Diabetes and Digestive and Kidney Diseases, had no experience in the health sciences before he came to study the problem of why so many Americans are overweight. “I didn’t even know what a calorie was,” he says.

This kind of outsider’s perspective can be invaluable when attacking a problem as difficult and entrenched as the epidemic of obesity in the U.S. Chow relates the story of starting work at the institute—a division of the National Institutes of Health—and finding a mathematical model created by a colleague that could predict “how body composition changed in response to what you ate.” The problem, as Chow describes it, was that the model was complicated: “hundreds of equations,” he told the Times. “[We] began working together to boil it down to one simple equation. That’s what applied mathematicians do.”

And what did Chow’s simple model reveal about the nature and causes of obesity? Basically, that we eat too much. “The model shows that increase in food more than explains the increase in weight.” Food in, fat out. Simple enough to be captured in a single equation.

Unfortunately Chow’s outsider’s perspective on the obesity crisis isn’t really an outsider’s perspective at all: it is the physicist’s perspective. Physicists have a long history of marching into other sciences with grand plans of stripping complex phenomena down to the essentials with the hope of uncovering simple fundamental laws. Occasionally this works. More often, they tend to overlook the very biochemistry at the heart of the process in question.

Chow’s conclusion is not just obvious—it’s a tautology. Because for Chow, a calorie is just a unit of energy. Eat more calories than you burn, and the energy must go somewhere. That somewhere is fat cells. The conclusion is built into the assumptions.

But perhaps a calorie is not just a calorie. Perhaps, as some prominent researchers argue, the body processes calories from sugar in a fundamentally unique and harmful way. According to this hypothesis, we’re not getting fat because we’re eating more. We’re getting fat because of what we’re eating more of. The biochemistry that explains why this would happen is complex—certainly difficult to include in a computer model—but that doesn’t make it wrong.

Ultimately experiments will decide if this hypothesis is true, or if it is not true, or if it is true but just one part of a nuanced understanding of obesity that includes biochemistry, microbiology, neurobiology, politics, economics and much more. The obesity crisis isn’t rocket science. It’s complicated.


About the Author: Michael Moyer is the editor in charge of space and physics coverage at Scientific American. Follow on Twitter @mmoyr.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. nihili 7:53 pm 05/15/2012

    I think that if you’ll reread Chow’s interview, you’ll find that his analysis is nowhere near as simplistic as you make it out to be. He clearly does not put forth the sort of simplistic calorie-in weight-out system you attribute to him. For example, he clearly points out that the same calorie increase affects obese people differently than it does non-obese people.

    Beyond that, your criticism is entirely misdirected as Chow isn’t addressing the the issue of how one individual gains or loses weight but rather the issues of why society as a whole seems to be gaining weight. Even given complex biological process of the sort you mention, it may still be the case that the societal problem of obesity is due almost entirely to an increase in food supply as Chow asserts.

    I don’t know whether Chow is right or wrong, but his arguments merit more than the dismissive straw man treatment you’ve given them. I would expect more, far more, of a SciAm editor.

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  2. 2. daviddriscollmsc 8:36 pm 05/15/2012

    Could I suggest that you replace the phrase ‘prominent researchers argue’ with ‘popular cherry-pickers of research suggest’? A quick pubmed search for Lustig and Taubes should set the record straight on how prominent they are, let alone how much actual research the contribute in this area!

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  3. 3. WRQ9 8:50 pm 05/15/2012

    Math can be used to predict obesity and a slew of other neurosis (including alcoholism, bulimia and depression to name a few) that all, I believe, arise by percentage from the same trends of cultural stimulus. If we address the national psyche as a whole, each trend affecting that whole will create a cumulative pos/neg effect resulting in a (by percentage) change in the numbers affected by these maladies.
    People are most comfortable, healthy and positive when they perceive an intrinsic value to their existence. A need for, not what they can provide, but what they are essentially. Any weakness in this perception will, within a segment of these individuals, express itself in one or more of these symptoms.
    Intelligent people are unlikely to be conned or placated by shallow response to stimulus such as this, gravity dictates, few exceptions exist. Because you don’t dare say something does not make it less true, or less meaningful.

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  4. 4. mike_midwest 8:50 pm 05/15/2012

    I read the interview and agree with the first comment. But I will try to get to the other links in the article.

    What I would really like to see is research on which policies are effective. For example I think all sales taxes on fresh fruits and vegetables should be eliminated. (Politically you will get much farther with local officials if you first talk about a tax cut.) The revenue loss could be made up by raising the taxes on high sugar drinks or non WIC approved cereals. Maybe 4% milk should have a higher tax than skim milk. Perhaps even the tax rates on restaurant foods could be differentiated. But we need the research on pilot projects to see what works.

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  5. 5. blindboy 9:08 pm 05/15/2012

    “Huge variations in your daily food intake will not cause variations in weight, as long as your average food intake over a year is about the same. This is because a person’s body will respond slowly to the food intake. ”

    Which is the exact opposite of my experience. I cut out junk food and lost 10 kilograms in six weeks!Individuals need to find out what works for them rather than rely on statistical averages or mathematical models. Try my method. Cut out cakes, biscuits, soft drink,fried food,take away from chain resaurants (pizza, fried chicken, burgers etc),dairy products except skim milk and no fat yoghurt and limit red meat to one or two servings a week.

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  6. 6. Dr. Strangelove 10:41 pm 05/15/2012

    Moyer, you can speculate all you want how complicated obesity is, or you can do a simple experiment. Get an overweight guy on a 2,000 Cal. daily diet, run 1 hour everyday and weightlifting 1 hour every two days. Do this for six months, then measure his weight.

    I bet against all the “it’s complicated” people that the guy will be in the normal weight range. I did it myself. I was overweight. After the “experiment” the doctors examined my body. They said I have the body of an athelete 25 yrs younger. Body mass is almost all muscle.

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  7. 7. Truthseeker 6:07 am 05/16/2012

    If you want to get a handle on obesity – at least in the U.S. – study the differences between what well-off people and poor people eat. Once upon a time, only the wealthy could AFFORD to get fat, the poor did well not to starve. When I was growing up and we saw an especially thin person, the adults would remark about how “poor” they looked. I didn’t realize how much things until I was showing my grandchildren my old High School Annuals. There were almost NO overweight teens in those books and the ones who were overweight stuck out like smashed thumbs.

    These days things are reversed. Go into any govt. housing project and you will see almost nothing but VERY obese people – men, women, small children – a preponderance of terribly obese people. But go to a shopping mall or other gathering place in the more affluent parts of town and you see a proportion of healthy to obese people more like when I was growing up in the 60s.

    What changed? What is different? Why are poor people fat now while the well-off are now thin? Study what people eat now versus what they ate in the latter half of the 60s and I suspect you’ll at least get a handle on the over all problem and perhaps see a solution – at least not a solution that involves creating the “Food Police”!

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  8. 8. JamesDavis 7:29 am 05/16/2012

    “Truthseeker”, you are correct. I noticed that too, you cannot help noticing it unless your are, like the movie says, “clueless”. People were not poorer or richer in the 50s and 60s, we all just ate different foods than what people eat now. The one restaurant in the town where I grew up had to cook like mom did or none of us were allowed to eat there. Now we have 4 fast food joints that lace their foods with chemicals, salts and sugars to enhance the taste of the food so you will eat more of it so they can increase their profits and the people have gained over 50 pounds in the last 20 years and now the skinny children are a minority. Here is something else I noticed: the skinny children are the ones who still eat at home and is not allowed the chemical laden fast food, and the parents still shop at the local farmer’s market so they can make the food fresh, and the children get very little meat and very little, if any, soft drinks; they drink mostly fruit juice with no sugar added and no sugar laden cereals and very little, if any, candy. It is not difficult to stay away from these chemical, salt, and sugar laden foods; your body forgets about the good taste of them in about two weeks.

    For these parents who say that they work hard and don’t have time to cook and sat down at the dinner table to eat are just lazy and lying. The Seven Day Adventist cook their meals before the sabbath starts on Friday and eat that pre prepared food, that they make fresh, during the sabbath and there are very few obese Seven Day Adventist. It is not difficult to do, you just have to make that first step and stay with it.

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  9. 9. glosen 8:54 am 05/16/2012

    This is not an esoteric concept. What I see having worked in the health field, at a weight-loss facility is what Chow has discovered. It is very simply calories in vs. calories out. Many people are addicted to bad carbs and sugar. This addiction is very similar to other addictions alcohol, drugs etc. The body is an amazing machine and anyone can overcome this issue. It seems like most Americans want a “magic pill” to fix their weight problem. It seems they are missing alacrity to correct their weight problem. My opinion, what do I do? Eat healthy, educate yourself on food products, avoid heavy carbs before bed, indulge, but not every day. Little changes that are sustainable are going to make a difference in your weight. Just like what kind of oil/gas you put in your car, the food you put in your body affects the way you feel. Food is fuel, the right kind can energize the wrong kind enervates. I am not trying to draft a polemic here, just my candid thoughts.

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  10. 10. geojellyroll 10:19 am 05/16/2012

    daviddris: “Could I suggest that you replace the phrase ‘prominent researchers argue’…”

    Excellent observation…it’s the norm that popular publiclations like ‘Scientific American’ inflate the status behind a remark or an article.

    ‘Scientists’…’experts’…’researchers’….often mean one or two grad students struggling to find some way to give a topic some promionenece so they can renew their funding.

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  11. 11. amoore_az 12:34 pm 05/16/2012

    @ blindboy: if you consistently maintained your new diet, for each day of the diet the average change in your intake came closer to zero for each day you maintained the behavior. Of course it would be nice if the author (Moyer) had bothered to ask for clarification.

    @Michael Moyer: did you bother to contact Chow or Kevin Hall (the mathematical physiologist he was working with that you fail to mention)? Considering the mathematical physiologist had hundreds of equations they were working with do you think that maybe some of them addressed your concerns? Did you bother to ask before posting this?

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  12. 12. GeekStatus 3:20 pm 05/16/2012

    It does boil down to calories and your sources that are supposedly saying otherwise aren’t actually saying otherwise. Thanks.

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  13. 13. Dr. Strangelove 10:35 pm 05/16/2012

    That link to Taubes article is making a simple thing complicated. Obesity is a medical condition of excessive body fat. What causes excessive body fat? That’s well-known: overeating and lack of exercise. Any empirical proof of this? Plenty. Go to weight reduction clinics. Their standard program is diet and exercise. And it always works, unless the patient has some genetic illness causing metabolic malfunction.

    Taubes makes a lot of fuss about fructose, insulin resistance, metabolic syndrome, etc. All these are symptoms associated with obesity. He makes a tortured argument that somehow, through a complicated process that we don’t yet understand, the symptoms are the cause of obesity.

    He states half-truths. Fructose is converted faster into fat. So what? When your body expends energy, it converts food into energy. If that’s not enough, it burns your body fat into energy. So the real problem is you’re converting food into fat faster than your converting fat into energy. That’s why you gain weight.

    Another half-truth. Fructose leads to excessive liver fat and insulin resistance. That will happen if you eat too much fructose relative to your body’s burning of energy. Again it goes back to diet and exercise.

    What about the lean guy with fatty liver? Well obviously his problem is not obesity. He has genetic disorder that’s making his metabolism malfunction. It has nothing to do with obesity, diet or exercise.

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  14. 14. gmperkins 12:30 pm 05/17/2012

    The question has never been do we eat too much (on average, Americans definitely do) but WHY we eat too much. The foods we eat affect our bio systems in different ways as well as other stress factors. Also, some foods we probably should be eating more of cost quite a bit more than foods we probably shouldn’t. This is the difficulty we face.

    And saying something is ‘complicated’ is just an overused phrase that now implies a lack of proper thoughtfulness and understanding as well as an unwillingness to make the effort to address and correct (in all genres). Leave ‘its complicated’ for the shallow emo textbooks and TV series that litter pop culture these days because I expect explanations from any topic I get emailed from SciAm.

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  15. 15. lpnetherton 8:40 pm 05/17/2012

    The solution, as has been outlined so well by others in this comment thread, is simply “No White Foods”. Cut out all refined flours, sugar, pasta, bread, potatoes, rice.

    All of this is directly related to the massive population-wide weight gain, and is simply for medicating the population into acquiescence. If they’re not hungry, they won’t be out on the streets with pikes, as in 1790 France.

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  16. 16. ccc1685 8:53 am 05/18/2012


    I’ve posted my response to Michael here:

    Carson Chow

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  17. 17. Mokurai 5:27 pm 05/18/2012

    This article is an excellent example of what I call the orders of thinking. The question is, what causes obesity, and the first (zero-order) answer is, eating too much. But this is not the answer the researcher Carson Chow gave. His equations balance each nutrient, not just total calories. This is a proper first-order analysis that bears on a variety of health questions, not just obesity.

    The question I would like answered, however, is the cause of the cause (second-order). Why can some people diet more readily than others? Why do particular diets work for some people and not others, and why do the groups not overlap completely? Why do some people get so hungry, and why can’t some of us resist hunger?

    It is known that the answer depends in part on biochemistry, in part on neurology/psychology, and in part on cultural factors. Within the biochemistry, we know of several hunger/satiation chemicals, such as ghrelin, leptin, and nesfatin-1. Their workings are not well understood, and it seems likely that there are more such chemicals involved in hunger, since we are all familiar with the feeling of being hungry for something in particular.

    We are also all familiar with the appetizer effect, in which restaurants give free bread or other food to patrons, knowing that eating the free food will cause them to order significantly more. But for some of us, known as carbohydrate addicts, it is much worse than that. Eating pasta, potatoes, bread, and so on, can keep us getting hungrier and hungrier all through a meal and into huge desserts.

    The Atkins diet is the converse of this. Not eating carbohydrates leads to decrease in appetite, often sustained so that dieters can lose significant amounts of weight without plateauing. We know a little bit about how that works (ketosis, that is, reduction in appetite in the presence of breakdown products of fat).

    We should also look at this in the third order. Given all of this biochemical-neurological complexity, how did it come about? Can we trace all of these factors, and their complex interrelations, to evolutionary survival, as we would expect? Certainly we can conjecture such explanations, but how about getting the data to discriminate among the conjectures, and turn one of them into a useful theory?

    So in fact, the issue is much more complicated than Michael Moyer makes out, and trivializing serious research is of no help at all.

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  18. 18. DouglasJohnLedet 2:24 pm 05/20/2012

    I am obese. On a 5’9″ frame, I pack 372 pounds.
    The reason I am obese is “I eat too much”.

    The new study is less than useful. Tell me something I don’t know.

    And I am not unique.

    I don’t want to eat too much and yet “My portions are too big”. It really is that simple. And yet it is the most complex issue in my life.

    Most of us who are obese, know it and we also know the cause is that we eat too much.

    Most of those who don’t are in self denial (There are those with real medical issues. I do not include these individuals. They are a “special” case and my heart goes out to them.).

    BUT the real question is, “Why do I eat too much?”.

    Am I emotional damaged?

    Do I overeat to compensate for a lack of quality relationship with woman, others, etc?

    Do I have genes that “make me” eat to cope with a coming shortage?

    I don’t know.

    Science is very good at how, when, etc.

    Not so good at “Why”.

    If you wish to “help” us, answer the question of “Why”.

    Until then, put your efforts to “other” projects where your skills are useful.

    Doug Ledet, Sebeka, MN

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  19. 19. Dr. Strangelove 10:47 pm 05/20/2012

    Doug, see a doctor to find out if you have other illnesses aside from being overweight. If you are ill, you need treatment. If you are just overweight, the cure is simple: diet and exercise. It’s not complicated. But it’s not easy. It’s hard. It requires enormous willpower. Losing weight is a mental game.

    It’s no different from training for a marathon. Anybody under 60, normal weight, without illness can run 42 kilometers. If your mind is determined to train, your body can do it. My training partner is 53. She runs marathons and beats the 20-yr old girls in the race. She started running only at 50 and now has the body of Sharapova.

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  20. 20. arynix 5:13 pm 05/21/2012

    so, if a person lacks “enormous willpower” for whatever reason, how would he/she obtain it? it comes back to the “why,” not just the “how,” as was eloquently stated earlier.

    by strict dieting and exercise for 6 months, I lost 29 pounds (almost 1/3 of what I needed to lose). then my father passed away. I regained that 29 pounds plus an additional 10 in about half the time it took me to lose the 29.

    why? did I all of a sudden start eating the equivalent of Thanksgiving at every meal? no, I simply stopped being so strict, in order to grieve without the added stress. the loss of my father fully overrode the “enormous willpower” I had conjured up for 6 months.

    my body naturally compensated for the “famine” it was experiencing by slowing the metabolism, and therefore, instead of just holding steady at the loss, it rebounded mightily in the other direction.

    all diets work. the problem is, not everyone can stick to it, presumably due to a lack of “enormous willpower.” furthermore, more than 80% of people who successfully slim down will gain it all back and more, resulting in the so-called yo-yo weight cycle.

    so, until the “why” is resolved in any given individual, the “how” is not only irrelevant, but, as in the case of yo-yo dieting, it can be MORE dangerous than never trying to lose in the first place.

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  21. 21. Dr. Strangelove 9:57 pm 05/21/2012

    You already answered the “why.” It’s willpower. The “how” is diet and exercise. Why do some people lose weight for good while others gain weight again? The 20% successful stick to regular diet and exercise. The 80% failure go back to old habits.

    When I get stressed, I don’t overeat. I exercise. It’s more effective in relieving stress. The more stress I get, the more vigorous my exercise. When stressed your body produces more adrenaline. You can actually feel more power in your muscles when you’re weightlifting.

    But if you lack willpower to continue, it can backfire and you may gain more weight. Just like in marathon, if you do it without proper training, your body will collapse.

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