Category Archives: calorie count

Why Posting Calorie Counts Will Fail, Part III: Calorie-restriction dieting doesn’t work long-term for most people

Previously in this series: Intro, Part I, and Part II.

The article on "Making Weight Loss Stick" is by Bob Greene, the personal trainer and "fitness guru" Oprah first started consulting with in 1996. Sadly, I don't think that's *meant* to be ironic. Oprah 2005/2009

To test whether turning [fat people] into thin people actually improves their health, or is instead the equivalent of giving bald men hair implants, it would be necessary to take a statistically significant group of fat people, make them thin, and then keep them thin for long enough to see whether or not their overall health then mirrored that of people who were physiologically inclined to be thin. No one has ever successfully conducted such a study, for a very simple reason: No one knows how to turn fat people into thin people.
Paul Campos, The Obesity Myth (2004)

Diets do cause weight loss…in the short term

People who think calorie restriction dieting “works” haven’t necessarily been duped by the diet industry or seduced by the prevailing nutritional “common sense” that weight loss and gain are a simple matter of calories in vs. calories out. Many of them believe it because their personal experience seems to confirm it, often repeatedly. Of course, “repeatedly” is part of the problem. Weight cycling—losing and re-gaining 5% or more of one’s total body weight—isn’t what dieters or public health policy makers are shooting for. Even people dieting with a specific occasion in mind, like a wedding or a high school reunion, would generally prefer to achieve permanent weight-loss.

But almost a century of research has shown that dieting—which usually involves calorie restriction—is not the way to do that. Studies repeatedly find that while eating less causes weight-loss in the short term, a majority of participants in weight-loss interventions focused on diet gain most of the weight back within 1 year and the vast majority (90-95%) gain all of it back within 3-5 years. Approximately 30% gain back more than they initially lost, and there’s some evidence that people who’ve lost and regained weight have more health problems than people who weigh the same, but have never lost and regained a significant amount of weight.

This is not controversial. Virtually every study of weight-loss dieting that has followed participants for longer than 6 months has found that the majority of dieters regain all the weight they lose initially, if not more. In other words, Oprah’s high-profile weight fluctuations are not the unfortunate exception to most dieters’ experience, they are the rule. A gallery of pictures of Oprah through the years illustrates the most frequent and reliable outcome of dieting:

Oprah in The Color Purple Screen shot of the infamous "fat wagon" episode first aired in the fall of 1988, when Oprah strode on set in what she proudly declared were size 10 Calvin Klein jeans after an Optifast diet, wheeling a Red Flyer wagon full of lard representing how much weight she'd lost  At the Emmy Awards, holding her third for "Outstanding Talk/Service Show Host"  Holding yet another Emmy at the end of that impressively-muscled arm, shaped with the help of trainer Bob Greene

             1985                           1988                             1992                             1996

 At the party celebrating the first anniversary of O Magazine  At the Academy Awards, wearing Vera Wang Presenting at the Emmy Awards presenting at the 2010 Oscars, possibly on the way back down again?

              2001                            2005                          2008                            2010        

I am not concerned (in this entry) with why calorie restriction diets fail—there are competing theories and perhaps I’ll try to tackle them some other time. However, when it comes to evaluating public health policies aimed at the general population, like posting calorie counts on menus, it doesn’t really matter why the kind of behavior it’s designed to encourage fails, especially when it fails so spectacularly. Whether the problem is that 90-95% of people don’t have the willpower to stick to calorie-restricted diets or that most peoples’ metabolic rates eventually adjust or both or something else entirely, continuing to prescribe calorie restriction to individuals seeking to lose weight is futile at best. Given the health problems associated with weight cycling and psychological distress caused by diet “failure,” it’s probably also dangerous and cruel. More on that another day, too.

The goal of this entry is to provide a condensed-but-comprehensive overview of the evidence that convinced me that weight-loss dieting—and particularly calorie-restriction dieting or eating less—does not “work” for most people. By “work” I mean lead to significant weight loss—at least 10% of starting body weight—that lasts for more than 3 years (in keeping with the clinical definition of “weight loss success” proposed by the 1998 National Heart, Lung, and Blood Institute [NHLBI] Obesity Education Initiative Expert Panel proposed). I honestly tried to keep this as short as possible and bolded the “highlights” if you want to skim. However, if brevity is what you’re looking for, see this 2007 Slate article.


A Meta-Review of the Literature

Of course, I’m not the first person to try to figure out what kind of picture decades of weight-loss research was painting. I found 14 reviews of weight-loss research in peer-reviewed journals (Mann et al 2007, Jeffrey et al 2000, Perri & Fuller 1995, Garner & Wooley 1991, Jeffrey 1987, Bennett 1986, Brownell & Wadden 1986, Brownell 1982, Foreyt et al 1981, Wilson & Brownell 1980, Stunkard & Penick 1979, Wooley et al 1979, Foreyt 1977, Stunkard & Mahoney 1976). And they all say basically the same thing: calorie-restriction diets don’t work long-term. Here’s how three of the most recent ones came to that conclusion, and one meta-analysis that claims to challenge the consensus, although it turns out that all they’ve really done is redefine “success.” 

Diets Don’t Work—Mann et al 2007 (free full text): This review of 31 weight-loss studies by a team of UCLA researchers was aimed at developing recommendations for Medicare regarding obesity prevention and treatment. They were only able to find 7 studies of weight-loss dieting that randomly assigned participants to diet or control groups and followed them for at least two years (the “gold standard” required to make causal claims about the effects of dieting). And the “gold standard” studies did not support the claim that dieting promotes significant or long-term weight loss:

Across these studies, there is not strong evidence for the efficacy of diets in leading to long-term weight loss. In two of the studies, there was not a significant difference between the amount of weight loss maintained by participants assigned to the diet conditions and those assigned to the control conditions. In the three studies that did find significant differences, the differences were quite small. The amount of weight loss maintained in the diet conditions of these studies averaged 1.1 kg (2.4 lb), ranging from a 4.7-kg (10.4-lb) loss to a 1.6-kg (3.5-lb) gain. (223)

They also examined 14 studies with long-term follow-ups that didn’t involve control groups. The average initial weight loss in those studies was 14 kg (30.8 lb), but in the long-term follow-ups, participants typically gained back all but 3 kg (6.6 lb). Of the eight studies that tracked how many participants weighed more at the follow-up than before they went on the diet, the average was 41% with a range of 29%-64%, and in every case was higher than the percentage of participants who maintained weight loss. In other words, participants were more likely to regain more weight than they initially lost than they were to maintain their initial weight loss. Although Mann et al note several problems with these studies, like low participation rates in the long-term follow-ups, heavy reliance on self-reporting as the primary or only measure of weight, and failure to control for the likelihood that some of participants were already dieting again at the follow-up, those factors should have biased the results in the direction of showing greater weight-loss and better long-term maintenance, not less.

Finally, they looked at 10 long-term studies that didn’t assign participants to “diet” or “non diet” conditions randomly. In general, these were observational studies that assessed dieting behavior and weight at a baseline time and then followed up with participants to measure changes in behavior and weight over time. Of those studies, only 1 found that that dieting at the baseline led to weight loss over time, 2 showed no relationship between dieting at the baseline and weight gain, and 7 showed that dieting at the baseline led to weight gain.

Their recommendation to Medicare:

In the studies reviewed here, dieters were not able to maintain their weight losses in the long term, and there was not consistent evidence that the diets resulted in significant improvements in their health. In the few cases in which health benefits were shown, it could not be demonstrated that they resulted from dieting, rather than exercise, medication use, or other lifestyle changes. It appears that dieters who manage to sustain a weight loss are the rare exception, rather than the rule. Dieters who gain back more weight than they lost may very well be the norm, rather than an unlucky minority. If Medicare is to fund an obesity treatment, it must lead to sustained improvements in weight and health for the majority of individuals. It seems clear to us that dieting does not. (230)

Long-term Maintenance of Weight Loss: Current Status—Jeffrey et al 2000 (free abstract or full text with umich login): A review of 20 years of long-term weight loss studies that describes the weight loss and regain among patients who participate in behavioral treatments for obesity as “remarkably consistent” (7) which is visually represented by lots of graphs of different studies on the long-term results of weight loss studies that all pretty much look the same:

Very low calorie diets vs. Low calorie diets (Wadden et al 1993)  Fat restriction vs. calorie restriction (Jeffrey et al 1995)

Diet only vs. Diet + exercise (Sikand et al 1988) People who were paid $25/wk for successful weight loss vs. people who weren't paid (Jeffrey et al 1993)

Basically no matter what researchers do, most dieters achieve their maximum weight loss at 6 months and then gradually regain all or almost all of the initial weight lost within 3-5 years, if not faster. They conclude:

The experience of people trying to control their weight is a continuing source of fascination and frustration for behavioral researchers. Overweight people readily initiate weight control efforts and, with professional assistance, are quite
able to persist, and lose weight, for several months. They also experience positive outcomes in medical, psychological, and social domains (NHLBI Obesity Education Initiative Expert Panel, 1998). Nevertheless, they almost always fail to maintain the behavior changes that brought them these positive results. Moreover, as we hope we have shown, efforts to date to change this weight loss-regain scenario have not been very successful.

Confronting the Failure of Behavioral and Dietary Treatments for Obesity—Garner and Wooley 1991 (free abstract or full text with umich login): Like Mann et al, Garner and Wooley were seeking to translate the available evidence about weight-loss dieting into recommendations for treatment—in this case, best practices for mental health practitioners seeking to counsel and treat overweight and obese patients. They note that short-term behavioral studies consistently show that modifications in eating and exercise behaviors lead to weight-loss, but that as the duration of studies increases, “over and over again the initial encouraging findings are eroded with time” (734).

The authors are particularly perturbed that poor results are often presented by study authors as positive. For example, an 1981 study comparing standard behavioral therapy with a weight-loss drug, or the therapy and drug combined found that all of the treatment groups lost a significant amount of weight in the first 6 months, and then all of the treatment groups showed significant re-gain by the end of the 18 month follow-up.the consistency in the curves is really eerie after a while...the 6 month nadir, the gradual incline; also, it is completely baffling to me how someone could look at this graph and think the most notable part is the gap between the three treatments at 18 months

Instead of concluding that all of the treatments had failed to produce lasting weight loss, the authors conclude that these results provide hope for behavioral therapy, because that group showed the slowest rate of weight re-gain:

This most recent study provides grounds for optimism as to the future of behavioral treatment of obesity . over the long run, behavior therapy clearly outperformed the most potent alternative treatment with which it has yet been compared. (734 in Garner and Wooley, 135 in the original)

This pattern is nearly as consistent as the finding that weight is gradually regained and many individuals eventually weigh more than they did at the start of the treatment. After four years, nearly all participants in nearly all studies gain back nearly all the weight they initially lost: Adams, Grady, Lund, Mukaida, & Wolk, 1983; Dubbert & Wilson,1984; Kirschenbaum, Stalonas, Zastowny, & Tomarken, 1985; Murphy, Bruce, & Williamson, 1985; Rosenthal, Allen, & Winter, 1980, Bjorvell & Rossner, 1985; Graham, Taylor, Hovell, & Siegel, 1983; Jordan, Canavan, & Steer, 1985; Kramer, Jeffery, Forster, & Snell, 1989; Murphy et al. 1985; Stalonas, Perri, & Kerzner, 1984; Stunkard & Penick, 1979. And yet, the authors of those studies insist that the diet interventions are “effective,” sometimes claiming that if the subjects had not dieted they would weigh even more. They almost never admit that the treatments completely failed to do what they set out to do, which is produce a clinically significant weight loss that can be maintained long-term. When they do admit that the results are “disappointing,” they frequently call for more “aggressive” treatments like very low calorie diets (VLCD or <800 kcal/day) or supervised fasting (which is no longer approved because of the risk of mortality).

Garner and Wooley also evaluate studies that used VLCD, some of which involved Optifast, the protein shake that Oprah used to achieve her 67 lb weight loss in 1988. Just like with other calorie-restriction diets, people on VLCD generally lose weight initially, although drop-out rates are much higher than in other weight loss studies (50% or more). Participants who stick to the diet typically maintain the weight loss for about a year, but regain most if not all of the weight they lost within three years and many gain more than they initially lost (Swanson and Dinello, 1970, Sohar and Sneh, 1973, Stunkard and Penick, 1979, Johnson and Drenick 1977, Drenick SC Johnson, 1980, Wadden et al., 1983, Wadden, Stunkard, & Liebschutz 1988, Hovel et al., 1988). Based on all of those studies, they conclude:

Although the rate and magnitude of weight loss have been the basis for recommending the VLCD, its most remarkable feature is the speed of weight regain following treatment. (740)

Garner and Wooley found only two studies of weight-loss dieting that reported better long-term results, and both had extremely low rates of participation in the follow-up and relied on self-reported weights. For example, Grinker et al (1985) reported that 55% of the participants in a residential treatment program had maintained a 5-kg weight loss based on the responses of only 38% of the original participants. They suggest that it seems far more likely that the low participation in the follow-up biased the results than that those studies are right and all the other ones or wrong and conclude:

It is only the rate of weight regain, not the fact of weight regain, that appears open to debate. While this may be discouraging to the individual intent on weight loss, it should also provide some solace to the many individuals who have failed at dieting and have attributed the failure to a personal lack of will power. (740)

It is difficult to find any scientific justification for the continued use of dietary treatments of obesity. Regardless of the specific techniques used, most participants regain the weight lost. (767)

They make the following recommendation to mental health practitioners:

We suggest that at the least, if weight loss is offered, it should be done with full disclosure of the lack of long-term efficacy and of the possible health risks [which, as they explain, include physical and psychological risks correlated with weight fluctuation]. It is further recommended that alternative nondieting approaches aimed at improving the physical and psychological well-being of the obese individual be given priority over dietary treatments as a subject of research and that such treatments be offered on an experimental basis. (767)

Long-term weight-loss maintenance: a meta-analysis of US studies—Anderson et al 2001 (free full text): As the title suggests, this is a meta-analysis rather than a review article, meaning rather than summarizing and evaluating what other studies found, they lumped together the data from 29 different studies. 13 of the studies involved “very low energy diets” (VELDs), 14 involved “hypoenergetic balanced diets” (HBDs) and 2 involved both—in other words, they were all calorie-restriction diets, and about half of them required participants to eat less than 800 kcal/day. The authors claim that no long-term randomized, controlled studies were available, and it’s unclear why they didn’t think studies like Jeffrey and Wing 1995 (discussed below) should count.

They don’t provide details for any of the studies individually, but do disclose that the number of participants ranged from 6 to 504, the length of treatment ranged from 8 to 30 weeks, average initial weight loss ranged from 3.5 to 37.9 kg for women and 6.2 to 44.2 kg for men, and follow-up participation rates ranged from 50% to 100% with a median of 82%. In other words, these were very different studies. Here are the results of their aggregation of the data:

again, what they're focusing on is the relatively small loss maintained by year 5 rather than, say, the precipitous drop from year 1 to year 2

The average weight loss at 5 years for both VELDs and HBDs was 3.0 kg, or ~3.2% of the participants’ starting weight and 23.4% of their initial weight loss. Anderson et al conclude:

These average values are higher than those reported in earlier studies and indicate that most individuals who participate in structured weight-loss programs in the United States of the type reported in the literature do not regain all of the weight lost at 5 y. of follow-up.

Sure, not all of the weight, only 76.6% of it. It still seems to me like a perversion of the idea of “success” to claim that these results show that calorie-restriction diets are “effective.” The average initial weight loss was 14 kg. If you lost almost 31 lbs and then regained 25 lbs, would you consider your diet a long-term success? Mann et al wouldn’t. In the 14 long-term studies without control groups that Mann et al evaluated, they also note an average maintenance of ~3 kg. They just don’t think that’s very impressive:

It is hard to call these obesity treatments effective when participants maintain such a small weight loss. Clearly, these participants remain obese. (Mann et al 223)

Interpretation/equivocation aside, there’s still some discrepancies between their analysis and the consensus in the other reviews which I wish I could explain. It’s not like this was a study of a new treatment—they relied exclusively on existing studies, at least some of which were also included in the reviews of the literature discussed above. However, some of the studies they included must have reported (possibly significantly) better results to bring up the average. Since they didn’t evaluate the studies individually, it’s impossible to tell from their write-up whether those studies involved some sort of strategy that made calorie restriction dieting “work” (and somehow didn’t attract widespread attention) or whether the results in those studies were biased by low participation rates in follow-ups, self-reporting, or some other factor(s).

A Closer Look at the Studies Themselves

I have not read every single study referenced in the review articles, although I have at least glanced at many of them. The ones I chose to explore in further depth here either 1) meet the “gold standard” of randomized assignment to diet/non-diet conditions and at least 2 years of follow-up or 2) are too recent to be included in the review articles.

Long-term Effects of Interventions for Weight Loss—Jeffrey and Wing 1995 (free abstract or full text with umich login): This is one of the seven studies included in the first part of the Mann review. 202 participants between the ages of 25 and 45 who were between 14-32 kg above the MetLife standards for the “ideal weight” for their height were randomly assigned to one of five experimental groups:

  • a control group which received no intervention
  • a standard behavioral therapy group (SBT) that received instruction on diet (including advice on how to follow a 1000-1500 calorie/day diet), exercise (including the recommendation to walk or bike 5 days/wk with an initial goal of burning 250 kcal/wk and gradually increasing that to 1000 kcal/wk), and behavior modification (including keeping food and exercise diaries. This advice was given in weekly counseling sessions for the first 20 weeks and monthly sessions thereafter for a period of 18 months.
  • a SBT + food group, which received the same counseling along with premeasured and prepackaged breakfasts and dinners for 5 days/week for 18 months
  • a SBT + $ incentive group, which received the same counseling along with up to $25/week  for achieving and maintaining weight loss
  • a SBT + food + $ incentive group, which got the counseling, meals, and money

In addition to the 18 months of the study, the participants were contacted at 30 months (a full year after the study ended) for an additional follow-up, which was completed by 177 (88%) of the original participants. Here are the results:

 is this shape getting familiar? 

All the treatment groups lost weight during the intervention, achieving their maximum results at 6 months. However, by 12 months—even though they were all still receiving the treatment, they were beginning to regain weight. By 30 months, there was no significant difference between any of the treatment groups and the control group. The authors wheedle a bit, claiming the difference “approaches levels of statistical significance” (.08), but are honest enough to admit in the end:

The overall results of this evaluation reemphasize the important point that maintaining weight loss in obese patients is a difficult and persistent problem.

Preventing Weight Gain in Adults: The Pound of Prevention Study—Jeffrey & French 1999 (free full text): This more of a “failure of low-cost educational interventions designed to encourage weight loss” than a failure of weight loss dieting per se, but it’s still relevant because 1) the experimental group “got the message” communicated in the educational intervention but gained the same amount of weight over 3 years as the control group and 2) calorie labeling is essentially a large-scale, low-cost educational intervention. The idea that education will make people thinner relies on the assumption that people would not be (as) obese if they only knew they were gaining weight, that they should eat more fruits and vegetables, that they should reduce their consumption of high-fat foods, and/or that they should get more exercise.

But most people do know all those things. In this study, 228 men and 594 women employed by the University of Minnesota and 404 low-income women, all between the ages of 20-45, were recruited to participate in a 3-year study. Half of the participants were assigned randomly to a control group and the other half were assigned to the “intervention” group, which received a 2-4 pg monthly newsletter called Pound of Prevention. The newsletter emphasized five themes:

1) weighing yourself regularly (at least once a week)
2) eating at least 2 servings of fruit per day
3) eating at least 3 servings of vegetables per day
4) reducing the consumption of high-fat foods
5) increasing exercise, especially walking

In other words, “common sense” nutritional advice, although not explicitly calorie reduction. The newsletter included recipes, suggested particular areas/routes in the local areas for walking, and included a return-addressed, stamped postcard asking participants to report their current weight and also answer whether they had walked for 20 minutes or more, eaten 2 servings of fruit, eaten 3 servings of vegetables, or weighed themselves in the last 24 hours. Intervention participants were also invited to take part in a variety of activities during the three years, including 4-session weight control classes, aerobic dance classes, free 1-month memberships to community exercise facilities, walking groups, and a walking competition. Additionally, half of the “intervention” group was assigned randomly to an “incentive” group who were eligible for a monthly $100 lottery drawing for members who returned the postcards.

All participants were evaluated in annual physicals where they were weighed, their height was measured, their dietary intake evaluated using a standard 60-item Food Frequency Questionnaire, and they were asked about behaviors like exercising, eating fruits and vegetables, decreasing fat intake, using “unhealthy diet practices” like laxatives and diet pills or liquid diet supplements, weighing themselves, and smoking. At some point in the study, a questionnaire was administered to test “message recognition.”

Participation in the “intervention” group was high—68% of postcards were returned, 80% of the participants reported having read most or all of the newsletters at their annual visits, and 25% participated in one or more of the extra activities. The “message recognition” test was somewhat successful—the intervention group was significantly more likely to identify the 5 targeted treatment messages as being among the best ways to prevent weight gain; however, even 66% of the control group endorsed the treatment messages. The intervention groups were slightly-but-significantly more likely to weigh themselves and more likely to continue practicing “health weight loss practices” as measured by a 23-item questionnaire. However, changes in BMI, energy intake, percent of calories from fat, and rates of physical activity were not significantly different between the control and intervention groups. All participants gained an average of 3.5 lbs over the course of the 3 years.

In short, the intervention was a failure. The authors conclude:

It is easier to teach people what to do than to persuade them to actually do it…. The overall impact on weight itself…was very weak, indicating that stronger educational strategies are needed or, alternatively education alone is insufficient to deal effectively with this important problem.

Weight Maintenance, Behaviors and Barriers—Befort et al 2007 (free abstract or full text with umich login): Based on the abstract, this study sounds like a success, but under closer examination, not so much. The data was collected at a university weight loss clinic where participants were recruited to follow low-calorie or very low-calorie (500 kcal/day) weight-loss diets followed by a maintenance program. The “weight-loss” phase lasted for 3 months during which participants consumed prepackaged meals and/or shakes. The maintenance programs ranged from 6 to 21 months and consisted of weekly or bi-weekly meetings at the clinic during which participants were counseled to follow a structured diet plan with a daily calorie goal and exercise 150-300 minutes per week. In 3 out of 4 trials, the participants were also encouraged to continue consuming the shakes/prepackaged meals.

Out of 461 participants who started treatment, 44 dropped out during the 3-month weight loss phase and 211 dropped out during the maintenance phase. They sent follow-up surveys to everyone who completed the 3-month weight loss phase (n=417), and got 179 back (46.6.%). The more recently participants had been part of one of the studies, the more likely they were to respond to the follow-up survey. Responders had only been out of treatment for an average of 14 months.

Their claim that a “majority” of the participants maintained their initial weight loss is based on them lumping together respondents who had only been out of treatment for 6 months with people who had been out of treatment for 24 months or more, despite the fact that—just like in every other study of calorie-restriction weight loss—the results showed that most participants gradually regain weight. As they admit:

Compared to participants who were out from treatment for 24 months or longer, those who were out for less than 6 months (P<0.05) or for 6–12 months (P<0.01) had significantly greater weight loss maintenance, both in terms of kg and percent of baseline weight.

What they don’t say is that the percentage of respondents who report maintaining their initial weight loss drops off precipitously after 24 months.

no graph; perhaps it would have been too damning?

Of the 31 respondents who’d been out of treatment for 24+ months, only 25.8% had maintained a weight loss of 10% of their body weight or more and 48.4% had maintained a weight loss of 5% or more. That means out of the original pool of 417 who completed the 3-month diet, only 8 had proven capable of maintaining weight loss equal to 10% of their body weight for more than 2 years and only 15 had proven capable of maintaining a weight loss equal to 5% of their body weight. Other participants might be able to maintain their initial weight loss—that data isn’t available, but the trajectory certainly doesn’t look good. And that’s based on the half of the participants who participated in the follow-up—as Garner and Wooley note, the higher the rate of participation and the longer the follow up, the less weight loss on average is maintained.

What About the National Weight Loss Control Registry?

Several of the studies and at least one person who commented on one of the earlier posts in this series mentioned the National Weight Loss Control Registry (NWCR) as evidence that people can indeed lose weight and keep it off. I’ve never disputed that. Even in the studies that show the least hope for long-term maintenance, there are exceptions to the general trend. But that’s what they are: exceptions.

According to the NWCR website, they have over 5,000 members, all of whom have lost at least 30 lbs and kept it off for at least 1 year; however, most of them have done far better—registry members have lost an average of 66 lbs and kept it off for an average of 5.5 years. As the research above suggests, that’s not remotely “representative” of people who attempt to lose weight. On the contrary, the entire raison d’être of the registry is to figure out what’s different about the 5-10% of dieters who lose significant amounts of weight and keep it off. The goal is to identify strategies that might help other dieters, but as the researchers who run the registry admitted in a 2005 article (free abstract):

Because this is not a random sample of those who attempt weight loss, the results have limited generalizability to the entire population of overweight and obese individuals.

Indeed, the kinds of things the registry members do are generally the same things the participants in most weight loss studies are counseled to do (or, in clinical settings, forced to do): most of them follow a low calorie, low fat diet, eat breakfast every day, weigh themselves at least once a week, watch less than 10 hrs of TV per week, and engage in very high levels of activity—420 minutes per week on average. The NWCR has yet to figure out what makes those things work for them and/or makes them capable of sustaining those behaviors when for most people, they don’t/can’t.

Collecting 5,000 success stories does not prove that dieting “works” for most people let alone that it’s the norm. Somewhere between 45 million and 90 million Americans diet to lose weight every year, most of them by attempting to reduce their caloric intake. According to a survey conducted in April 2010 by a private consumer research firm on behalf of Nutrisystem, 30% of Americans have dieted repeatedly—an average of 20 times. Unsurprisingly, weight loss attempts are more common among overweight and obese people. If calorie-restriction dieting “worked,” America would be a nation of thin people.

Conclusion: Putting the burden of proof back where it belongs

Traditionally, researchers assume that a treatment is not effective until they have evidence that proves otherwise. The reverse is true in regard to weight-loss dieting: most people assume dieting is effective for long-term weight loss and challenge anyone who believes otherwise to prove that it doesn’t—not that that’s difficult, given the consistent failure of most weight-loss interventions to produce lasting results. I have not been able to find one long-term, randomized, controlled study that shows that dieting works (i.e. a statistically significant group of people following a calorie-reduction diet losing a clinically significant amount of weight and keeping it off for more than 3 years). Instead, what all the research to date shows is that the most reliable outcome of calorie-restriction dieting is short-term weight loss followed by weight regain.

I suspect the stubborn persistence in prescribing calorie-restriction dieting as a weight loss strategy in spite of the available evidence probably has a lot to do with dominant and deeply-engrained attitudes about fatness, meritocracy, virtue, and effort. People exhibit remarkable cognitive dissonance when it comes to the research on weight loss—they hold up exceptions as the rule and claim that the 90-95% of people for whom calorie restriction dieting does not produce weight loss must simply not be trying hard enough. 

Imagine this scenario playing out with any other condition—imagine that instead of weight, we were talking about some kind of rash that was widely considered unattractive and thought to be correlated with a variety of other health problems. There’s a treatment that showed promise in short-term trials. In virtually every study, most of the people who get the treatment experience significant improvement in their symptoms, with peak results around six months. However, in longer-term studies, there’s a reversal. Just as consistently, the vast majority of sufferers—at least 75% and usually closer to 90 or 95%—experience a gradual return of their symptoms. For approximately 30-40% of participants, their symptoms actually get worse than before they started the treatment. Only 5-10% show lasting improvement. Of course you would want to do more research to figure out why the treatment works for that 5-10%, but in the meantime, would you keep prescribing it to everyone with the same skin condition?

Even if the problem is that only 5-10% of them fail to use the treatment as instructed—say, it’s a topical cream that only works if you apply it every hour on the hour and people get fatigued, especially by trying to wake up at night to put it on. If 90% of the affected population can’t use the treatment effectively, the results are the same as if the treatment never worked in the first place. Well, except for that part where 30-40% of them end up worse off than before they started the treatment…

So even if the calorie counts on menus were accurate, and people could accurately and reliably estimate how many calories they burn, and they did choose lower-calorie options at least some of the time, and they didn’t compensate by eating more on other occasions…in other words, even if the calorie counts worked the way they were intended to, the best you could hope for would be short-term weight loss. There’s no reason to believe the policy—even under ideal conditions—would have a lasting effect on most Americans’ weight or health.

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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