I’ve just read Dr. Traci Mann’s popular book, Secrets from the Eating Lab, which came out in April (and is hence a “new book” at my library at the moment…). I had some real hopes for this book on dieting, obesity, and the psychology of eating. Mann has some fame in behavioral psychology, and her lab at the University of Minnesota is influential. Plus she just wrote an op-ed that Oprah Winfrey’s investment in WeightWatchers is a smart business move because diet failure, which leads to repeat customers, is a built-in and stated profit strategy for the company. Mann points out it’s the same logic that runs casinos. Big revelation? probably not, but still a good point and illustrative of the circular logic in popular American diet culture.
So about Secrets from the Eating Lab. The tone of the book is personable and it’s a quick read–a couple of hours will cover it. But…it’s not really a very good book and it makes Mann look a little like the huge parade of airheaded “pundits” who show up on Fox News and Good Morning America and Dr. Oz to talk about emotional eating right before presenting a plate of “healthy treats” that turn out to be brownies.
OK, it wasn’t quite that brainless. I even liked a lot of what Mann had to say about how to live an integrated life and not obsess over weight. But the book is a very good example of why someone who’s reasonably expert in one facet of diet research may not be the right person to interpret other areas for the public.
The behavioral studies are interesting and entertaining. Although the findings are not altogether news anymore, the lab setups she and her team used to demonstrate them are fun to read about. A sample of the psych experiment findings, which are the strongest part of Mann’s book:
- The eating style of your companions is likely to influence you pretty strongly when you eat as a group. Her lab tested this in an entertaining series of experiments.
- “Determination and willpower” is more wishful thinking than a successful diet strategy for a lot of people, and structuring your environment is more effective.
- Keeping a bowl of treats even more than arm’s length away from you reduces your likelihood of grazing, and if you actually have to get up and walk to get more, you probably won’t.
- People eat more when distracted with screentime or eating while driving or whatever than when focusing on their food.
- Smaller plates lead to greater satisfaction with less food.
- Offering vegetables at the school cafeteria before serving the rest of lunch, and without competition from french fries, gains a much higher rate of takers than when there are other foods available.
- Announcing foods as “healthy” is a turn-off.
- Most intriguingly, “comfort food” is no more effective than any other food, or even no food, for recovery after an emotional shock.
All of these findings mesh with common sense, and few of her recommendations are implemented as regularly as one would like in daily life at school or work. But the behavioral studies from her lab are only a small part of the book, one or two chapters in the middle. Where Mann runs into trouble is nearly everywhere else. Put bluntly, she’s way out of her depth in the larger world of academic obesity research, and neither she nor most of her readers or even, crucially, her book editor seem to know it.
The main themes of Secrets from the Eating Lab are 1. that diets don’t work, 2. obesity is not the deadly killer everyone assumes it is, and 3. therefore you should stop obsessing and be healthy in other ways, for example by exercising to relieve stress.
These claims are stated as blanket facts rather than opinions she wants to explore, even when she bolsters them with studies. Outside of her own lab’s experimental framework she makes fundamental and glaring mistatements and assumptions of fact that can easily be disproven. The result is not markedly better than what you might expect from a modestly competent high school debate team’s background prep for the season topics, “Do Diets Work?” and “Does Obesity Kill?”
In the “diets don’t work” chapter, Mann scours the literature for a largeish number of diet studies in which subjects attempted to lose weight, then winnows the 300 or so studies down to about 26 that meet her criteria of a randomized controlled study with reasonable participant recruitment and retention. Although some studies demonstrated short-term weight loss or differential success between two test diets over the course of weeks, months or a year, longer followup revealed no net loss and a large degree of regained weight among participants, and most of the studies had a lot of dropouts before completion. Moreover, most were less than carefully conducted and relied on self-reported weight and diet recall from the subjects rather than weigh-ins and so on.
Well, fair enough. But she doesn’t look at more recent and stringent work, as a nutrition researcher would be expected to. And she doesn’t really explore what the behavioral environments of the experiments might have contributed–something she might have been able to lend better insight into. She also doesn’t really look into the reverse case, whether and how experimentally-induced obesity with high-calorie diets causes measurable harm. She claims there’s no practical way to do that but in fact some recent studies have. Several were published early and prominently enough that she could have been aware of them and had time to include them in the book if she hadn’t believed them impossible. (And of course there’s Morgan Spurlock’s famous self-experiment documentary, “Super Size Me”…)
She concludes the chapter with the declarations that weight loss for a year or so is worthless, that no one is capable of losing more than about 30 pounds anyway, and caps it with “Diets don’t work.” I’m not sure why she brushes off a 30-pound loss, or even a 15-pound loss, as “doesn’t work”, especially as she does acknowledge that it substantially reduces the risk of developing Type II diabetes in many people.
I’m not sure why she didn’t look into the question of whether weight loss for a couple of years might still provide some health benefit, even if subjects couldn’t keep all the weight off forever or had to lose weight more than once in their lifetimes. I don’t know whether anyone’s even studied this question but it seems like it would be important to find out before dismissing temporary weight loss as a failure. It would at least be interesting.
And of course almost everyone knows someone who has lost significant weight, well above 30 pounds, and kept it off for more than five years or even a decade or more. What makes these people different from the people who yo-yo or have trouble losing more than 10 or 20 pounds? The mindset factors alone would be fascinating, and Mann would presumably be qualified to discuss or study them herself, but in this book she neither explores any of these questions nor looks for studies that do. That’s a stunning lack of curiosity for someone in behavioral research.
For that matter, what does she actually mean by “diets”? In her discussion she lumps all diets together with the assumption that they’re all useless (again, no further exploration). It’s a question that grew on me as I read the rest of the book, and by the end I was forced to conclude, a bit disturbed, that she simply does not know herself.
As an illustration of what else Mann might have presented on the experimental record for diet research, if she’d been genuinely curious and not stuck with a fixed idea to “prove” in cherry-picking mode, let’s look at another reviewer’s approach.
The record of haphazardly conducted diet studies is well-trodden history–it certainly was back in 2008, when nutrition researcher Chris Gardner of Stanford University gave a video chalk-talk about the state of research on the effectiveness of low-fat vs. low-carb diets. Although he agreed with Mann that a majority of previous diet studies were too loosely designed to discover much, he also took into account–and ran–quite a number of well-designed studies that looked beyond the “diets don’t work very well” mantra and parsed out some meaningful differences between those who did lose substantial weight in those studies and those who didn’t on a variety of popular and standard diet plans. He discovered that different diet proportions between carb and fat calories worked better for different subgroups. And again, this was more than seven years ago, well vetted and well publicized.
The arguments and evidence Mann presents for her chapter on “Obesity is Not Going to Kill You” are a lot more troubling and less plausible than her diets-don’t-work review. Her tendency to present simplistic declarative messages about science for lay readers gets her further into the weeds. She argues that because people don’t die directly of obesity and that their lifespans aren’t remarkably different these days from people of healthier weight, that obesity doesn’t really matter as much as it’s been hyped by the media and medical establishment.
But we know that dying is not the only problem with illness. You may not die just of being obese, but you will certainly increase your risk of debilitating cardiovascular and metabolic conditions considerably, and the list of ills made more likely by obesity keeps growing–acid reflux, asthma, sleep apnea, and on and on. You will almost certainly have to take a lot more medication with a lot more side effects and cost than someone of weight in a less risky range. You will suffer a lot more disability and immobility in the meantime.
We do know this–we see it in our families and among our communities. Our doctors are seeing a lot more of these conditions than they used to. It’s not in dispute.
From the glib arguments she made, it’s clear to me that Mann really doesn’t grock epidemiology at all. You can’t do absolute cause-and-effect tests on chronic diseases that affect a whole population with randomized controlled studies, which she calls the “gold standard” of scientific proof. But risk factor identification on this level is pretty important information and usually has to come first.
Messy as it is compared with the nice, neatly controlled “did subject A take the carrot or the cookie when alone or with dining companions” questions Mann is used to testing, epidemiology is a valuable way of finding out crucial information for public health.
Chronic disease conditions–heart disease, diabetes–develop gradually and incrementally over decades. You need very large numbers of subjects to see broad population trends and identify major risk factors that apply to most people with reasonable certainty. To tease out real information from the huge swath of individual variability, you need more extensive and sophisticated statistical analyses than Mann’s lab probably ever conducts.
So what is Mann doing here? For a smart and seemingly earnest researcher in the mainstream to do something this irrational and contrarian in print, there has to be a driver…other than money and daytime tv pundit gigs. And there is.
The book is predicated on Mann’s professional status and presentation of objective evidence for discarding the diet-or-bust mentality in treating obesity. Ironically, none of her own behavioral studies address whether diets work or whether obesity kills, not even tangentially. Her studies are about “Will you choose the healthy food even though all your friends are reaching for chips and french fries?”
If she kept the claims and discussion limited to what she actually works on, there would be less feeling of her having read superficially and cherrypicked studies outside her field to fit a personal conviction.
Because the other glaring problem with this book is that the fairly sizeable remainder of it is not about the science of diet, obesity or eating behaviors at all. It’s an attempt at relating to the reader through personal anecdotes, empathy with the evils of temptation and tips for avoiding it, an exhortation that what really matters is to be okay with yourself at any size and just exercise (she prefers yoga and running) and it generally reads like a standard women’s lifestyle magazine article.
Mann attempts to empathize with the presumably overweight reader via her own taste for irresistible “yummy treats,” most of which are nutritionally poor desserts and snacks. Standard tip example: not driving by your favorite doughnut or ice cream shop helps you avoid temptation. Even the book cover slants this way by featuring an ice cream sundae with a bunch of M&Ms scattered around it.
Her advice on exercise being valuable even if you never lose weight is actually right enough, given that exercise is an independent risk reduction factor for cardiovascular disease and diabetes. She doesn’t point that out, perhaps because she doesn’t quite recognize the independent risk factor idea from epidemiology.
Her advice on not letting overweight stop you from living a full life is okay too and makes sense human kindness-wise, but does not relate inherently to scientific findings.
And yet she tries to bolster these vague bits of lifestyle advice with a handwave mention of cortisol levels and stress and inflammation as a sciency-sounding foundation for saying so. It’s even true that those physiological factors have been identified as one, but not necessarily the major, potential pathway connecting lifestyle risk factors to chronic disease. Here Mann really does no better than use it as a bit of pop-sci decoration on a standard diet-and-fitness piece. You’ve been seeing the same in your local paper and in Shape or Prevention or Woman’s Day for years now.
She recycles the emphasis on cortisol and stress in a chapter on discrimination against obese people in school and the workplace. The studies in this chapter are sociological for the most part–much like the data on pay gaps between men and women, or red-line mortgage lending practices that discriminate against African Americans. It’s not that the issue is unimportant or the data wrong, but Mann doesn’t present more than a presumptive or speculative argument for detrimental health effects of discrimination here. Nor does she give any evidence-based takeaway message for what overweight and obese people can do to counter the possible health effects. It would be perfectly reasonable for a civil rights advocacy group to string arguments together this way, even though the logic is kind of chopped, but it is actually out of place in this book–well, at least if the book were consistently about behavioral research on eating. Here it amounts to special pleading for a cause rather than something that really relates to any kind of scientific research on obesity and diet.
Where is this all emotionalized stuff coming from, anyway? I want to come back to the point that Mann never examines what she means by diet, because the further I read, the more this seemed to be the driver for the book. The diet and lifestyle recommendations chapters are much more personal and presumptive than truly evidence-based. She repeatedly muddles her scientific presentation on diet studies and behavioral experiments with a series of arbitrary stances ranging from “dieting is painful” to “discrimination is what stresses overweight people and makes them ill.”
Mann declares she has only ever once been on a diet–for a grand total of two weeks, as a teenager with a group of friends who made some truly inane and nutritionally silly choices of what to eat. Bread was forbidden but snack crackers were allowed…? Some things with mayonnaise were okay and others weren’t? Cheese but not milk? Apparently it was a hell she never wanted to revisit, and it appears to color her convictions that “diets don’t work,” diets are miserable and make your breath smell bad, they change your personality and give you delusions, and that it is neither necessary nor even possible to lose more than about 30 pounds, almost no matter who you are or what you try.
She never looks back and considers that:
- teenagers don’t know a whole lot about nutrition
- what she and her friends tried was never going to be a plausible diet or even substantially different from what the girls were already eating
- it takes more than two weeks to lose significant weight even on a plausible diet and
- she probably shouldn’t base her understanding of diets on that lone childhood experience.
But since she does, I have to say she still doesn’t know what “diet” and “works” mean in any concrete, consistent and meaningful sense for the rest of us.
Most of these convictions about pain and suffering don’t hold water for well-constructed meal plans with balanced and adequate nutrition when they are actually tested.
“Lifestyle” diets such as the DASH Diet and the Idaho Plate Method provide plenty of fresh food and flexibility. You can live on them whether you’re attempting to lose weight or not–they used to be the norm in a lot of places, before burgers and fries took over. Mann doesn’t seem to include them in her definition of “diets,” but they do happen to be significantly below the daily caloric intake of many overweight and obese people, and a significant number of subjects in the DASH diet trials of the 1990s lost weight on them without that having been an objective of the trial.
They are not extreme or painful, either, as different as they are from the Standard American Diet of today. As Robert Lustig has found, patients who start eating a plate method or DASH diet with more vegetables and real food, less processed or fast food, and moderate portions overall stop feeling cravings fairly quickly even with significantly fewer calories–within a matter of days in some cases.
As to bad breath and depression, I don’t know what kind of diets Mann was referring to, and perhaps neither does she–ketogenic extreme diets, perhaps? It does not appear that she really looked into the details of any of the study diets that reported these symptoms, and it is quite clear from her anecdotal passages that she does not have experience–lab or personal–with sustained adherence (beyond a week or so) to balanced weight loss diets. Gardner, in the Stanford Medcast lecture I mentioned earlier, does go into that and his insights are actually insightful.
So perhaps we should be asking the fundamental question–which Mann doesn’t. What actually constitutes a plausible weight-loss or weight-control diet?
Not everything that calls itself a diet is one. Does it add up to fewer calories than you’re currently eating? How can you determine that for sure? Is it nutritionally adequate and balanced so you don’t become ill? Or does it raise warning flags for saturated fat or sodium or over-the-top carbs? Is it really a meal plan that adds up, or just a diet book with slogans, fancy mysterious explanations, exhortations to buy diet supplements or join an online club with a membership fee, eat a lot of avocado, and then a slew of recipes? You see all these things on the Dr. Oz show, in popular magazines, online, in diabetes cookbooks…they’re colorful and exotic-sounding and comforting and all the rest of it, but underneath the glitz they’re all a mishmash of self-contradiction, wishful thinking and profit-mongering, apparently even Weight Watchers if Mann is correct. All the brownies in the world are still extra calories, after all. No matter how much avocado you stuff into them.
When I look at a proposed diet plan, I look for at least the nutritional stats in the proposed menus and meal plans to deliver weight loss if you follow them literally. Calories have to add up to the stated daily total when I cross-check them with a nutrient database. Portion sizes have to be stated clearly enough so I can calculate for them. There has to be real and affordable food that includes vegetables, not a bunch of mostly-processed substitutes or big nutritional imbalances. And I don’t like to see anything that undercuts the main goals of weight loss for diabetes or cardiovascular disease prevention and management or urges you to buy special ingredients, dietary supplements, or club memberships.
If you don’t follow such a diet accurately and for a reasonably long period of time, that’s another story. But at least it starts out with the potential to work, you don’t need to be afraid of it, and it probably won’t harm you in the meantime.