Category Archives: calorie

Why Posting Calorie Counts Will Fail, Part II: Most People Don’t Know How Many Calories They Burn

Introduction and Part I of this series.

click for USA Today article

Few stories that begin, “Many Americans clueless…” can really be called “news.” Nonetheless, a recent study made headlines earlier this month by confirming what research has shown time and again: most people don’t know how many calories they supposedly burn. The 2010 Food & Health Survey by Cogent Research asked respondents (1,024 adults “nationally representative of the US population based on the Census”) to estimate how many calories someone of their age, height, weight, and activity levels “should consume” per day. Only 12% got within 100 calories +/- their Estimated Energy Requirement (or EER, the formula currently used by the USDA) and 25% wouldn’t even venture a guess. The remaining 63% were just wrong. This seems to pose a problem for the claim that publishing calorie counts on menus will improve public health. Logically, if people don’t know if they burn 10 or 10,000 calories in a day, which is the range of estimates collected in another survey, conducted in 2006 at the University of Vermont (full text with UMich login), knowing how many calories a particular menu item contains probably isn’t going to do them much good. The campaign is called "Read 'em before you eat 'em" (the slogan in the little purple circle. Image from nyc.gov

The new calorie publishing policy actually includes a provision to help address this problem—in addition to the calorie counts of all menu items, menus will also have to publish the average daily calorie requirement for adults (2,000 Kcal). New York City also attempted to address the problem of calorie ignorance when it instituted its calorie count requirement by launching an ad campaign aimed at drilling the 2000/day calorie requirement into people’s heads.

But that’s not the kind of calorie ignorance I’m concerned about. For one, I don’t think the success of calorie counts in reducing obesity or improving public health depends on people keeping strict caloric budgets. Enough people have internalized the belief they ought to eat fewer calories that the numbers could be useful as a point of comparison regardless of how many people can accurately estimate how many calories they supposedly burn based on their age, height, weight, and activity level. Even if you’re under the mistaken impression that you’re Michael Phelps, if your goal is to consume less energy, choosing between the 250-calorie sandwich and the 350-calorie one is a simple matter of figuring out which number is smaller. IF calorie counts were accurate, and they inspired at least some people to consistently chose lower-calorie items, and at least some of those people didn’t compensate for those choices by eating more later or being less active, and some of them continued to burn the same number of calories despite eating fewer of them, then the counts would actually have the intended effect. The magnitude of the effect might be small, but it would be in the right direction.

Of course, that’s a big “if.” I already addressed the first condition (calorie counts are often wrong), and will be looking at the next two (people don’t order fewer calories but if they think they have they are likely to compensate later) in more detail in later entries. The problem of most people not knowing how many calories they burn is related to the third condition—the mistaken assumption that people will continue to burn the same number of calories even if they reduce the number of calories they eat.

In other words, the problem isn’t that too few people know that the average adult probably burns something in the vicinity of 2000 calories per day. The problem is that metabolism varies. It doesn’t stick to the formula based on height, weight, age, and activity levels. Most people don’t know how many calories they burn because they can’t know, because it’s dependent on lots of factors that formulas don’t and can’t account for. And one of the things that usually causes people to burn fewer calories per day is eating fewer of them. This starts to get at one of the other reasons I don’t think posting calorie counts will have the desired effect: it’s true that eating fewer calories often leads to short-term weight loss, but the vast majority of people either get hungry and can’t sustain the energy deficit or their bodies adjust to burning fewer calories and erases the deficit. Either way, almost all of them regain all of the weight they lost, and often more.

The Rise, Fall and Return of the Calories-in/Calories-out Myth

The idea that weight gain and loss is simple matter of calories in versus calories out also dates back to William Atwater (the turn of the 20th C. USDA scientist who was into burning food and excrement). Before Atwater, most people believed that the major nutrients in food were used in entirely different ways—proteins were thought to be “plastic” and used exclusively for tissue repair and growth, like little band-aids that the body could extract from food and simply insert where necessary; fats were similarly thought to be extracted from food and stored basically intact; only carbohydrates were thought to be transformed by digestion as they were burned for fuel. The discoveries that protein could be converted to glucose by the liver and that carbohydrates could be transformed into body fat were both seen as wildly counterintuitive and controversial. Some physicians continued to give advice based on the earlier principles as late as 1910. RMR = resting metabolism, which should probably be shaped more like a big empty question mark

However, in the last few decades of the 20th C., Atwater and others managed to convince an increasing number of people that a calorie was a calorie was a calorie—that all of the major nutrients could be burned for fuel and that any fuel not immediately consumed in heat or motion would be stored as fat. The idea of seeking an equilibrium between calories ingested and calories used was first advocated by Irving Fischer, a Yale economist who drew a parallel between Atwater’s new measure of food energy and the laws of thermodynamic equilibrium and market equilibrium. This theory had widespread appeal in the age of Taylorism and scientific management, which coincided with the first major national trend of weight-loss dieting and the aesthetic ideal of thinness represented by the Gibson Girl and the flapper.* Caloric equilibrium was a way to apply the same universal, rational logic thought to govern the laws of chemistry and the market to the body. From the 1890s through the 1920s, the calorie reigned supreme. As historian Hillel Schwartz says:

The calorie promised precision and essence in the same breath. It should have been as easy to put the body in order as it was to put the books in order for a factory” (Never Satisfied: A Cultural History of Diets, Fantasies, and Fat 1986, 135).

That human bodies don’t reliably obey this logic in practice didn’t matter then any more than it seems to matter to most contemporary advocates of caloric algebra. Skeptics noted, even then, that many fat people seemed to eat much smaller meals than thin people, and that some people could reduce their intake to practically nothing without losing weight while others seemed to eat constantly without gaining weight. But the theory of caloric equilibrium is powerfully seductive, not just because of its simple, elegant logic, but also because it seems to “work,” at least in the short term. People who reduce the number of calories they eat do tend to lose weight initially, often at approximately the predicted rate of 1 lb/3500 calories. That offers a kind of intermittent reinforcement. When it doesn’t work or stops working, people scramble to come up with excuses—either the dieter’s estimates of how much they were eating must have been wrong, or they were “cheating” and eating too much (more on this in the entry on why calorie-cutting diets fail).

However, caloric math hasn’t always been the dominant nutritional theory (despite what many people claim). In thefrom Atlas of Men, Sheldon's most popular book 1930s and 1940s, as weight-loss dieting became less popular and feminine ideals got a little plumper again, nutrition science became more concerned with the psychology of appetite—often relying on Freudian-influenced theories about how traumatic childhood experiences and sexual dysfunction might manifest as insatiable hunger—and a new theory of body types.

The theory of somatotypes was initially developed by William Sheldon in the 1940s as part of an attempt to use measurements of the body to predict personality types and behaviors, like criminality. He proposed a sort of three-part continuum between three extremes: the thin ectomorph, the fat endomorph, and the muscular mesomorph, based on the three layers of tissue observed in mammalian embryos. It was similar to the medieval medical theory of different physical constitutions based on the balance of humors (blood, phelgm, bile, etc.) but with a new sciencey gloss and some nationalist overtones—Sheldon noted, for example, that Christ had traditionally been portrayed as an ectomorph (supposed to be cerebral and introspective), and suggested that therefore Christian America would have a military advantage over the mesomorphic Nazis (supposed to be constitutionally bold and arrogant). Somatotypes were later used to customize diet and exercise plans, but at the time, they were primarily embraced as a way to describe and justify the apparent differences in peoples’ ability to be thin. Unlike the algebra of calories in/calories out, somatotyping suggested that no matter what they did, endomorphs could never become ectomorphs. They simply did not burn calories at the same rate, and their bodies would cling stubbornly to fat, especially in the abdominal region.

Sheldon’s theory, like many projects with eugenicist overtones, fell out of favor somewhat after WWII, especially after the embryonic tissue theory was discredited. However, his somatotypes live on, primarily among bodybuilders and competitive weightlifters, perhaps because they still need some way to explain individual differences in outcomes for identical (and rigorously-monitored) inputs. There are also subtler echoes in the idea that people have individual “set points” or genetic predispositions towards certain body types, which isn’t meant to imply that there’s no validity to those theories—I think it seems far more likely that there are genetic components to body size than that all family resemblances are environmental. However, as the new calorie labeling policy exemplifies, the universalizing logic of calories in/calories out is back with a vengeance. Almost every popular diet plan today, with the exception of paleo/low-carb/grain-free diets, is based on creating a calorie deficit (and in practice, many low-carb diets also “work” to the extent that they do at least partially by reducing caloric intake).

The point of this little history lesson is that the extent to which people ascribe to either the theory of calories in/calories out or the theory of intransigent body types seems to have more to do with what they want to believe than the available evidence. Calories-in/calories-out may appeal to Americans today for different reasons than it appealed to the enlightenment rationalist seeking to find and apply universal laws to everything. I suspect that it has a lot to do with normative egalitarianism and faith in meritocracy, e.g. anyone can be thin if they eat right and exercise. The idea of predetermined body types, on the other hand, appealed to mid-century Americans eager to identify and justify differences and hierarchies of difference. But in every case, the evidence is either cherry-picked or gathered specifically to support the theory rather than the theory emerging from the evidence, which is complicated and contradictory.

*Before the 1880s, the  practice of “dieting” and various regimens like Grahmism (inspired by Sylvester Graham), the water cure, and temperance were concerned more with spiritual purity or alleviating the discomforts of indigestion and constipation than achieving a particular body shape or size. Graham’s followers actually weighed themselves to prove that they weren’t losing weight, because thinness was associated with poor health.

So What?

Even if most people can estimate how many calories they burn on an average day now with some degree of accuracy, and the calorie counts help them eat fewer calories than they did before or would have otherwise, there’s no guarantee that they’ll continue burning the same number of calories if they continue to eat fewer calories, which they would have to do for the policy to have long-term effects. In fact, given >6 months of calorie restriction, most people appear to burn fewer calories or start eating more and any weight lost is regained. So either the calorie counts will change nothing about how people order at restaurants and there will be no effect on their weight or health. Or they will have the desired change on how people order… but there still won’t be any effect on their weight or health.

But boy am I glad we have easier access to that critical information.

Why Posting Calorie Counts Will Fail, Part I: The Number Posted is Often Wrong

Introduction to this series here.

image stolen from some article about the new policy that I lost track of because I had 70 tabs open  When you see 450 posted, that might really mean 530. Or more.

Publishing caloric values right on the menu seems straightforward and transparent. The numbers offer what appears to be a simple way to compare items no matter how different they are based on what many people believe is, as Margo Wootan said, the “most critical piece of nutrition information.”  But even setting aside for a moment the issue of whether the number of calories should be the most important factor governing food choices or all calories are equal, there are problems with the numbers themselves.

Give or take 20%…but almost always give

According to a recent study at Tufts where a team of nutrition scientists led by Susan Roberts used a calorimeter to measure the actual caloric value of 39 prepared meals purchased at supermarkets and restaurant chains:

Measured energy values of 29 quick-serve and sit-down restaurant foods averaged 18% more than stated values, and measured energy values of 10 frozen meals purchased from supermarkets averaged 8% more than originally stated. Some individual restaurant items contained up to 200% of stated values and, in addition, free side dishes increased provided energy to an average of 245% of stated values for the entrees they accompanied. (Journal of the American Dietetic Association; full-text is subscription only—here if you have UM library permission)

As Roberts told Time, she decided to do the study because when she was trying to follow the diet advice in her own book, substituting prepared or restaurant meals, “the pounds stopped dropping off. Just as suspiciously, she always felt full” (more on the idea the fullness means a diet must be failing when I get to the issue of why calorie-restriction doesn’t work for long-term weight loss).

It’s worth noting that the results of the study didn’t reach statistical significance “due to considerable variability in the degree of underreporting.” However, they “substantially exceeded laboratory measurement error” and—as noted above—the average discrepancy was 8% or 18% higher, it didn’t even out. However, the average is actually within the Federal regulations—from the same Time article:

Federal regulations are strict about the accuracy of the net weight of a package of prepared food, which must be at least 99% of the advertised weight. When it comes to calories, the count can be a far bigger 20% off. The Federal Government plays no role in checking the calorie claims in restaurants, which means it’s up to the states to handle the job — with the predictable patchwork results.

What Roberts’ research suggests is that calorie counts aren’t just wrong, they’re wrong in one direction. As anyone who’s ever tried to count calories knows, a difference of +18% could be devastating to a diet. Say, for example, you think you burn 2000 calories/day, like the supposed average American adult, and you’re trying to generate a ~250 calorie/day deficit through your diet. Assuming you continue to burn 2000 calories/day, that diet should make you lose about 1/2 lb per week or 26 lbs in a year. However, if you were actually eating 18% more calories than the 1750 you’ve budgeted, or 2065 calories/day, and the caloric algebra worked perfectly, you’d gain 6.8 lbs in a year instead.

Even if you’re being reductive, food is more than the sum of its parts

One factor that may work in the opposite direction: the method used to determine the caloric  content of food may systematically overestimate how much energy most people get from some foods. A quick primer on the calorie (most people who are reading this probably already know this, but since lots of people don’t): a nutritional calorie is a measure of the energy contained in food. The base unit, a gram calorie, is the amount of energy required to heat 1 gram of water 1 degree Celsius. A nutritional calorie is a kilocalorie (kcal) or “large calorie” (C), the amount of energy required to heat a 1 kg water 1 degree.

William Olin Atwater c. 1900 from the USDA via the Wikimedia CommonsHere’s the part a lot of people don’t know: the caloric value on labels is calculated according to the “Atwater system” named after the USDA chemist William Atwater, who spent his career burning food and excrement (cue Bevis & Buthead laughter). Based on the formula Metabolizable Energy = Gross Energy in Food – Energy Lost in Secretions, Atwater came up with average energy values for each macronutrient: 9 Kcal/g for fat, 4 Kcal/g for protein, 4 Kcal/g for carbohydrates, and 7 Kcal/g for alcohol. For the purposes of nutrition labeling, even though fiber is technically a carbohydrate, it’s subtracted from the total carb weight before the calories are calculated since it’s not digested.

However, there appears to be considerable variation within macronutrients. Sucrose burns at a lower temperature than starch and isolated amino acids vary in their heat of combustion. Additionally, the Atwater system doesn’t account for differences in how macronutrients behave in when combined—for example, fiber seems to change the amount of fat and nitrogen that turn up in feces, which suggests that its effect on caloric value might not be entirely accounted for by simply subtracting fiber grams from the total carbohydrates. And, as you might expect, “variations in individuals are seen in all human studies” (Wikipedia).

The differences between estimated calories and the actual caloric value (as measured by a bomb calorimeter like the one Roberts’ team used in their study, which still might not correspond exactly to how food is turned to energy in the human digestive tract–I’m not entirely sure how calorimeters account for fiber given that fiber is combustible even though it isn’t digestible) might not be very large—but perhaps more importantly, the discrepancies probably aren’t consistent. The Atwater system is probably more accurate for some foods than others, and seems especially likely to overestimate the energy value of high-fiber foods and distort the differences between starchy and sugary foods.

That might help to explain the discrepancy seen in studies on nuts: in controlled nut-feeding trials, people eating more calories in the form of nuts don’t gain the weight that they should based on their greater energy intake. Additionally, they excrete more fat in their feces (Sabate 2003, American Journal of Clinical Nutrition). This is similar to another issue I mentioned in the introduction—not all calories are the same—but it’s not actually the same problem. Non-random variance in the reliability of caloric estimation means that even if all calories were the same, the numbers on the menus might not be accurate, i.e. the way we estimate calories might not correspond reliably to the amount of energy people actually derive from the food they eat.

So what?

Well, this means that there are (at least) two possible ways that providing consumers with “more information” in the form of calorie counts might actually lead to worse decision-making:

1) Even if people do base their decisions about what to order on the posted calorie counts, they might end up getting many more calories than they want and eating more than think they are.

2) Certain kinds of foods—including high-fiber foods and nuts, which might be “healthier” than items with lower posted calorie counts according to more holistic metrics—might have misleadingly high calorie counts based on the Atwater system. That could dissuade customers from ordering them or restaurants from offering them in favor of less “healthy” foods that may  have lower counts based on the Atwater system but actually provide more energy.

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Why Posting Calorie Counts Will Fail: Introduction

Calories on menus are already a fact of life in New York City and were set to appear in a handful of states like California and Oregon in 2011. Instead, thanks to a provision in the health care legislation Obama signed in March, they’ll be required nationwide. The policy calls for all restaurant chains with 20 or more locations to publish calorie counts for all items on all menus. The policy also applies to vending machines, buffets, and bars. McDonalds menu with calorie counts from the website for the film Fat Head, click for info. I'm surprised to see that the fries actually aren't the best Kcal/$ bargain--the burgers and even the McChicken give you slightly more bang--or burn--for your buck. The profit margin on fries must be astounding.

The policy’s advocates and authors claim that it will reduce obesity rates and improve public health. In a press release from The Center for Science in the Public Interest, Margo Wootan, a nutritionist who helped write the calorie count part of the bill said:

"Congress is giving Americans easy access to the most critical piece of nutrition information they need when eating out…. It’s just one of dozens of things we will need to do to reduce rates of obesity and diet-related disease in this country…. Menu labeling at restaurants will help make First Lady Michelle Obama’s mission to reduce childhood obesity just a little bit easier.” (CSPI press release)

In an interview with the LA Times, she expanded on the logic of the claim: 

"People will be able to see that the order of chili cheese fries they are considering will be 3,000 calories.”

Well, probably more like 400500. But how could she be expected to know that before the law goes into effect?

Kelly Brownell, director of the Rudd Center for Food Policy and Obesity at Yale told the NYTimes that even if some consumers ignore the information, it will affect enough people to create a public health benefit. However, he also hedged his bet—saying that even if it doesn’t make people eat better, it’s an issue of rights as much as an issue of health:

“You don’t need a study that proves anything,” Mr. Brownell said. “You just have a right to know.”

Proof? Who needs proof? His disclaimer is savvy, because now in 5 or 10 years if obesity rates are still the same* or higher and there’s been no significant decrease in cardiovascular disease, diabetes, cancer, or any of the other conditions correlated (albeit often weakly) with obesity, Brownell can claim we’re still better off knowing than not knowing.

I’m not so sure. While I don’t think posting the number of calories is likely to have a significant, negative impact on public health, nutrition is one realm where more information isn’t always better. The usefulness of information always depends on its reliability, relevance, and people’s ability to place it in meaningful context. Calorie counts fail on all three measures, which is why I suspect the new policy isn’t going to have the desired effect on obesity rates or public health.**

Here are a few of the problems with calorie counts I’ll address in this series:

1) The number posted is often wrong (a problem for reliability)

2) Most people don’t know how many calories they burn (a problem for meaningful context)

3) Even though calorie restriction is a highly effective short-term weight loss strategy, it doesn’t work long-term (at least for 90% of dieters) (a problem for relevance)

4) Not all calories are equal (another problem for relevance)

Furthermore, the limited evidence available so far about how calorie counts on menus affect purchasing decisions based on the New York City law is mixed. That calls into question the mechanism by which the policy is supposed to improve public health. Apparently, knowing the calorie content of menu items doesn’t necessarily reduce the number of calories people purchase. And that’s before even beginning to try to measure whether purchasing fewer calories on single visits to restaurants actually leads to weight loss or if people just compensate by eating more on other occasions or eating more often.

One response might be: well, it can’t hurt. I’m also not so sure about that. While I don’t think it’s likely to make public health worse, by reinforcing the idea that your health (or your weight) is based on the number of calories you eat, it may prevent people from taking steps that would actually improve their health, which the preponderance of evidence suggests that calorie-restriction dieting will not.

Part I in this series, on why the number posted is often wrong, coming later today.

*The rate of increase in obesity has already been slowing down so even if it plateaus, that’s not necessarily evidence this or anything else is “working,” it may simply mean that obesity rates have reached an upper limit.

**Two separate issues which are often unjustly conflated. For more on that, see Paul Campos’ The Obesity Myth, J. Eric Oliver’s Fat Politics, Glen Gaesser’s Big Fat Lies, or Michael Gard and Jan Wright’s The Obesity Epidemic: Science, Morality, and Ideology—if you feel like I’ve said that before, it’s because I have. The reason I bring them up again and again is that they completely changed my thinking about nutrition, fatness, and health. The authors of those books all—independently—examined the evidence for the argument that obesity is dangerous and all reached the same conclusion: it’s not, and the belief that it is is based on some shockingly bad science. They also argue convincingly that the actual increases in Americans’ weight in the last few decades are actually quite modest (it’s the rate of people being defined as obese that’s trumpeted, not the amount of weight people have gained on average and some of the increase is based on changes in the definition of “normal” or “healthy” with no medical justification); that the correlations between obesity and disease or early mortality—many of which are quite weak—can be entirely explained by other factors that also happen to be correlated with BMI like differences in physical activity, income, and insurance status; and that weight-loss dieting, especially low-fat and calorie-restrictive dieting, do more harm than good. You don’t have to take my word for it. Substantial portions of the books are available for free online, as are many of the studies they cite (including the CDC study that revised the widely-cited statistic that overweight and obesity causes 300,000 deaths per year in the U.S. and said, effectively, “Actually make that 26,000 and by causes we mean correlates with.”)

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