Do dietary guidelines do more harm than good?
January 23, 2008
I wouldn’t even ask such a silly question if the American Journal of Preventive Medicine wasn’t going to publish a paper arguing just this point. Along with one of the editors of that journal, I wrote an editorial commenting on the paper, to which its authors added a rebuttal to our editorial. The authors argue that the government has no business issuing advice based on weak evidence. I would agree except that evidence will never be as good as we wish it would be because research on human nutrition is really, really hard to do. And when it comes to diet, dietary guidelines are not exactly radical; the basic advice hasn’t changed in 50 years. I summarize it like this: “eat less, move more, eat plenty of fruits and vegetables, and don’t eat too much junk food.” Michael Pollan gets it down to 7 words: “Eat food. Not too much. Mostly plants.” The Dietary Guidelines published in 2005 may take 70 pages, but in general, they say pretty much the same thing.
Dr. Nestle, you say this a lot - “the basic advice hasn’t changed in 50 years.” But didn’t it change drastically with the McGovern Commission in 1977? Before the government codified the low-fat hypothesis into policy, Ancel Keys and his diet-heart hypothesis were controversial. That is, what Keys said 50 years ago was not the basic advice. So by my count, we’ve had 30 years of the same advice, not 50.
I’m less than 50 years old, and I remember that when I was a kid in the 70s, everybody knew that the way you lost weight was to give up bread, spaghetti, and sweets. Diet plates in restaurants used to be a hamburger patty with no bun and a side of cottage cheese. Don’t you remember this? That was the basic advice then. It wasn’t until the 80s that we said, “Oh, so it’s not the bread, it’s the butter!”
So how can you say the basic advice has not changed? It’s changed drastically. No, that’s not a strong enough expression of what happened. It’s been turned on its head!
Furthermore, supposing we did have 50 years of the same advice, or 100 years, or 200 years? Has it made us any thinner or healthier? We generally blame this on people not following the advice, but this is very hurtful to people who really do conscientiously follow the guidelines and fail to lose weight or improve their health. It is also insulting to people who try to follow the guidelines but fail to stick with them because the current “basic advice” fails to supply adequate energy for exercise or to prevent overeating by satisfying the body’s nutrient requirements. When are nutritionists going to stop blaming the victim and ask the obvious question of whether the advice we’ve been giving is sound?
Comment by Migraineur — January 23, 2008 @ 6:06 pm
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Pingback by medicine » Blog Archive » Do dietary guidelines do more harm than good? — January 23, 2008 @ 8:39 pm
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Pingback by diet » Blog Archive » Do dietary guidelines do more harm than good? — January 24, 2008 @ 2:05 am
I really liked Marion’s response!
Lots of her passages stood out, here are a few:
“The fallacy of inferring causality from a temporal association is familiar to methodologists, but the suggestion of causality in this case is also naive on policy grounds, because it assumes that a guideline could singlehandedly change a nation’s eating habits.”
“The promulgation of a guideline to lower fat intake was a component of this secular trend, not its origin. In creating products low in fat but with similar calorie levels, food companies were responding to a secular trend, not to a dietary guideline.”
“However, to fault the dietary guidelines because people behave this way [consuming more calories in the wake of promotion of low-fat foods] is to suggest that a smoker who gains weight after quitting should not have been counseled to stop smoking.”
“Withholding dietary guidance out of fear of unintended consequences elevates the duty for caution above the duty to inform, a notion that might itself be considered paternalistic.”
“To scapegoat guidelines is to oversimplify the complex and to obfuscate the necessary—albeit difficult—task of confronting these larger determinants of obesity.”
Comment by Bix — January 24, 2008 @ 9:31 am
@ 1:
Just to defend Ms. Nestle, and other nutritionists out there, it is worth noticing that it is rarely if ever actual nutritionists making all the pronouncements that you are describing. The closest to a nutritionist it typically comes from is one of the TV doctors (like Dr. Gupta or some such). The vast majority of all the contradictory nutrition recommendations come from the media looking for good copy, and from diet book writers looking for good copy. Neither are particularly interested in how solid the information is, how vetted the studies are, or how likely it is to damage our health (or at least, confuse the bejezus out of us). Actual nutritionists, that I have seen, rarely ever weigh in on these issues, and really have stuck with the same basic advice for decades–lower your calories, eat lots of fruits and vegetables.
Comment by Robyn M. — January 24, 2008 @ 12:30 pm
I apologize. My first post came across as harsher and ruder than I intended. Dr. Nestle, I do agree with you on many things, including the importance of including more vegetables and whole foods and excluding the processed junk that food manufacturers want to sell us.
Where I disagree is that keeping healthy is a matter of eating less and moving more, which seems simplistic to me. I’d accept it, even if it were simplistic, if I thought it were true. But I don’t think it is. A while ago you wrote that you hadn’t yet read Good Calories, Bad Calories. I wonder if you’ve gotten to it yet. Taubes’ claim that obesity is, on a cellular level, the same as starvation seems to me a brilliant hypothesis, and if true, should cause us to see in a whole new light why fat people eat more and move less than thin people. If Taubes is right, it’s not because fat people are lazy and greedy, it’s because a diet rich in carbohydrates provides energy in a form that obese people’s bodies find difficult to utilize for anything but storage. Thus, obese people don’t move much because their cells aren’t getting proper energy, and they eat more because they are genuinely hungrier than thin people. Change to an alternate energy source that an obese person can burn readily, and the problems of fatigue and hunger go away.
This, in turn, would imply that some of us (how many of us? I suspect lots), by luck of the draw, are born with bodies that do better avoiding certain types of food than by limiting the total amount of food.
I see myself in Taubes’s hypothesis, by the way. I do not limit my calories at all, and the last time I bothered counting calories I was losing weight (less than a pound a week, but still a loss) on about 2,300 to 2,400 calories a day. But I have cut out whole categories of foods that were problematic. On the other hand, I never succeeded in losing an ounce, and in fact gained weight at a rate of about 10 lbs a year, when I tried to follow the high-carbohydrate Food Pyramid. “Tried” is the operative word. I couldn’t stick to it most of the time, because I was too hungry.
If I sounded angry, it’s because “eat less, move more” really is hurtful if eating more and moving less is a symptom, not a cause, of obesity. It would be like telling a cancer patient who is fatigued that he’d just feel better if he got up and moved around; therefore his fatigue is his own fault.
Does that make more sense than what I said before?
Comment by Migraineur — January 24, 2008 @ 2:05 pm
I once weighed a hundred pounds more than I do now, 120, on the same 5 foot seven inch frame. What changed besides the shrinking waistline? To put it simply, I ate better and moved a hell of a lot more. I cut out liquid calories almost entirely, started consuming less and less meat, and payed more attention in general to what I was putting in my mouth. At the same time I started excercising regularly, mostly cardiovasuclarly, and eventually took up long distance running.
Now nearly seven years later, I am a vegan having run three marathons with a 3:01 pr. I eat a diet that probably consists of 80% carbohydrates and I have to make a concerted effort to maintain weight with my training regimen. Anecdotal evidence doesn’t prove anything but I feel the consensus opinion among nutritionists and food scientists for the past thirty years is both straightforward and accurate; it certainly works for me and many who I know.
Comment by Sean — January 24, 2008 @ 7:14 pm
Sean — Wow. I’m impressed by any positive results. I tried to be a vegetarian, and I almost immediately gained 25 pounds, and became very ill (GI problems, fatigue, skin rashes, reflux, and other unpleasantness). I stayed ill for two years — the entire time I was a vegetarian. I went on the Zone Diet, which increased my protein intake from about 30 grams a day to 80 (which means a lot of animal protein), and reduced my carb intake from about 200 grams a day to 120. I’m not sure how much fat I was eating, but on the Zone it was limited to 36 grams per day, monosaturated. I had a complete reversal of my illness in four weeks. The variance between human beings and their metabolism is quite impressive.
Comment by Spider — January 24, 2008 @ 10:27 pm
“The variance between human beings and their metabolism is quite impressive.”
Yep. That’s the real reason I am against dietary guidelines. That’s not to say I’m against professional advice, or information sharing. But the one-size-fits-all approach is so clearly wrong. I’ve been hanging out on a lot of nutrition blogs lately, and for every person who has lost weight and improved their health on a low-carb, moderate-protein, high-fat diet, there is another person who has lost weight and improved their health on a low-fat, low-calorie, high-carb diet.
Now, what you never hear is, “I lost weight and improved my health eating Snackwells!” So the one consistent piece of advice that everyone should get is, “Ditch the junk food.” But as long as the USDA has a split personality (”protect agribusiness!” “advise Americans on what to eat!”), that advice is never going to be heard from official corridors. One example: the current USDA advice is “make half your grains whole,” which really means, “it’s OK to make the other half junk.”
Comment by Migraineur — January 25, 2008 @ 10:35 am
[…] Nestle, by the way, mischaracterizes the editorial when she asks, on her blog, Do Dietary Guidelines Do More Harm Than Good? The editorial itself does not recommend doing away with guidelines, instead suggesting that […]
Pingback by Standards of Evidence for Dietary Guidelines « The Migraineur — January 28, 2008 @ 9:08 am
Wow. I’ll have to write a more extensive blog on this when I get some time. A few comments for the moment:
I’ll have to look up how they define “evidence based”. There is a truly rigorous mathematical basis (called Probability Theory) for weighing the evidential support of hypotheses - the problem is that almost nobody uses it. The reasons for this state are historical and sociological, but the end result is the current situation, where we’re supposed to choose from “lies, damned lies, and statistics”. If this is the case for the referenced analyses, then the supposed “analytical rigor” is built on a mathematical house of cards.
That a lot of papers, pages, etc. show support for a particular hypothesis does NOT imply that hypothesis is “true”. Another hypothesis might have greater significance based on the evidence, but you can’t know that unless you ask the question. I would bet that the quoted evidence on the benefits of a low-fat/low-calorie diet (e.g. Ornish) are equally (if not better) explained by the carbohydrate hypothesis, because the combination of calorie restriction and increased intake of fruits/vegetables almost certainly represents a drastic decrease in glycemic load and insulin response. But if you don’t specifically compare that hypothesis to the fat hypothesis, you can’t possibly know which is better supported by the evidence. The carbohydrate hypothesis has the added support of information from molecular and cellular biology, which seems to be routinely ignored for the purposes of devising dietary guidelines. I am unaware, for example. of no such molecular/cellular evidence supporting hypotheses of saturated fat (by itself) as the cause of disease (maybe it exists, and I just haven’t found it - please point me to such evidence if anybody knows of it).
The referenced “1400 pages [of] meticulous analyses of the scientific evidence” are meaningless unless you consider ALL of the evidence. Further, when looking at results of many different studies/publications, one needs to assess how much added weight they give to a hypothesis. If Paper B simply parrots Paper A, nothing is added. But publication counts are frequently used as an argument for the “truth” of a hypothesis, which is nonsense.
Finally, the authors blur the line between providing information and making recommendations. When a government or other scientific agency provides information, it’s just saying “here’s what we know”, and it is up to the individual to make behavioral decisions. Recommendations imply that the decision of what is best has already been made. Thus consumers don’t have to decide - the government has already decided the optimal behavior. This is generally accompanied by a paucity of actual information - which makes sense, as the decision has already been made for you. If you have no decision to make, then why would you need any information? We then are faced with situations where we have no choices, such as with school lunches. The organization that supplies lunches for my son’s school is quite proud of how it follows the food pyramid. But it also offers no alternatives. That’s fine for me, since I can make him a lunch that I feel reflects my information about what is healthiest. But for most parents, the overwhelming alignment of government, school, lunch providers implies overwhelming evidence that they’re all recommending the right thing. But only the government has bothered to examine any evidence at all, and a subset at that. Everyone else is just parroting the “recommendations.”
Comment by Dave Dixon — February 11, 2008 @ 1:47 pm
Speaking of evidence, how about the Tufts university study on the 2005 guidelines that concluded:
“…Americans are at risk of having excessive energy intake even if they follow the 2005 FGP food serving recommendations.”
http://jn.nutrition.org/cgi/content/full/136/5/1341
When one is willing to make recommendations based on weak evidence, one must be willing to accept the possibility that the recommendations are off the mark.
And if you do get to read Good Calories, Bad Calories you will see a history of the abrupt change in dietary recommendations 50 years ago. It was not about the science.
Comment by Ms Spry — February 11, 2008 @ 2:55 pm
“Granted, dietary guidelines can
be improved, but they are not the culprit in the obesity epidemic. The larger concerns are poverty and an environment that promotes overeating and inactivity.”
So it’s our environment that promotes overeating? I’m sorry, but this is extremely shortsighted.
I followed the basic food pyramid for years, and was a lacto-ovo vegetarian for several of them. So why was I constantly sick with colds, flu’s and allergies? Why was I overweight, and steadily gaining? More importantly - why couldn’t I stop eating?
Because I couldn’t stop. My diet was firmly rooted in organic, whole grain products (pastas, artisan breads etc) and low-fat dairy/soy products, with lots of veggies and fruits and some vegetable oils (canola, olive)for cooking or on salads. Breakfast, for example, might be a high-fibre multigrain cereal with low-fat vanilla soy milk and blueberries. I’d be starving an hour later. Eventually, I was hungry all the time, and dealing with intense cravings for starchy foods; so bad, in fact, that I either had to chew gum or leave the house after dinner to keep myself from eating a box of crackers (whole grain, of course) or bag of rice cakes.
I had constant inflammation, acne, and a distended abdomen. My nails broke, my hair split, and my digestive system was a mess. My moods were all over the place (usually down) and my energy was low. I managed to run a few miles a day, plus weight train - made no difference at all to my weight or appearance, or health.
Finally, I stopped eating grains and soy. All, and I mean all, of my health problems cleared up within a few months. I replaced the grains (and low-fat everything) with meat and animal fats. My gut was silent and functioning perfectly for the first time in years - no more constipation (or the opposite). My skin was soft, and acne-free. Nails and hair - healthy and strong. Allergies, even hayfever - gone. Best of all, my weight dropped, the bloating vanished, and my moods totally turned around - no more anxiety or depression. Energy went through the roof, and I finally started seeing results from my weight lifting!
My point? Dietary guidelines that assume “X” food is healthy while “Y” food is unhealthy don’t take into account the vast differences between people, nor do they even begin to examine our evolutionary past and what foods and/or preparation methods served us well. There are healthy vegans, vegetarians, omnivores and carnivores out there. (I am not going to address political/ethical arguments here - they are invalid in this context) Why are we so determined to claim one way as “right” when it’s clearly not so? Whose needs are we serving?
I reclaimed my health only when I looked outside of the mainstream recommendations and began to do my own research and experimentation. How many others would benefit from doing the same? Rather than trying to sway people to “do the right thing” (even though it’s not helping), would it not make more sense to - gasp - reexamine and redefine our idea of “right”? (Or, maybe, chuck the concept altogether)
Comment by Tracy Bradley — February 12, 2008 @ 2:35 pm