American College of Physicians: Internal Medicine — Doctors for Adults ®

Thursday, August 13, 2015

Ending the big, fat debate

Achieving a clear understanding of the health effects of dietary fats requires a challenging slog through a thick tangle of opinions. These days, it's rare to get through any given news cycle without contentions about dietary fat, expert and otherwise, coming at us from every quarter. The preoccupation, especially intense now, has a rather long lineage.

Call to Action: Let's End the Big Fat Debate
• It is time to end the big, fat debate by focusing less on nutrients, and more on foods.
• Some of the most nutritious foods are extremely low in fat (e.g., broccoli, spinach, blueberries) and some, high (e.g., walnuts, almonds, flaxseeds, avocado, salmon). Some of the world's most nutritious diets contain little fat (e.g., most vegan diets), and some, rather a lot (e.g., most Mediterranean diets).
• Focusing just on fat, or any other nutrient, does not lead reliably to a wholesome, health-promoting diet. Focusing instead on a dietary pattern of wholesome foods in sensible combinations does lead reliably to an appropriate balance of all nutrients.
• Let's talk less about nutrients, and more about foods. If we get the foods right, the nutrients will take care of themselves!
• Source: Katz DL, Meller S. Can we say what diet is best for health? Annu Rev Public Health. 2014;35:83-103

Ancel Keys began suggesting we should restrict our intake of dietary fat, saturated fat in particular, as far back as the 1940s. Other notables joined that chorus soon after. Robert Atkins first suggested we should liberalize our fat intake and cut carbohydrates instead in the 1970s, although his message made its greatest impact when reprised two decades later. Recent years have brought us point and counter-point about fat and other nutrients with increasing frequency, and apparent acrimony.

The better part of a decade and a half ago, we were told that everything we had heard about dietary fat might be a Big, Fat Lie. After a dozen years to chew on that, we received much the same memo last year, as if new, and told it should it all come as a Big, Fat Surprise. So it is the big fat debate has raged for decades, and all the while our population has generally gotten fatter, and sicker.

Is butter back, or isn't it? Should there be any cap at all on our intake of dietary fat, and if not, is more now better? Why the seemingly interminable Big, Fat Debate- and what really is the truth about dietary fat and our health?

Recent opinion pieces in both JAMA, and reiterated in the New York Times, ostensibly call for an end to the “ban” on a limited intake of total dietary fat. In doing so, the authors invoke the report of the 2015 Dietary Guidelines Advisory Committee, which does indeed relegate to the dustbin of dubious ideas the proposition that we should honor some specific cap for total fat. The DGAC report preferentially emphasizes the foods we should eat for better health, some of which, like nuts, are natively high in fat, and correspondingly deemphasizes nutrients, although they are, of course, addressed.

Inevitably, the attendant commentaries go mostly the other way, focusing primarily on fat, and secondarily on the foods delivering it. In the context of competing claims about dietary fat, considerable clamor, and general confusion, that focus is understandable. I favor the former approach, however, foods over nutrients. Either way, a cap on dietary fat intake has clearly outlived any utility it ever had.

That is not to say all dietary fats are good for us. Some, like the trans fats being expelled from the food supply by the FDA, are quite simply toxic. The proliferation of trans fat through the food supply, as replacement for highly saturated tropical oils, was intended to advance public health. We have long had evidence that the opposite was achieved; trans fat is clearly more potently inflammatory and atherogenic (i.e., contributes to the formation of atherosclerotic plaque in arteries) than any naturally occurring fat in our diets.

As for the saturated fat that prompted the trans fat boondoggle in the first place, it is neither as sinister as its most ardent detractors contend, nor as saintly as its New-Age apologists propose. Saturated fat represents a complex and diverse family of compounds of quite variable character. Some members are still convincingly linked to important adverse health effects, notably increased risk of cardiovascular disease. Others, notably stearic acid, have been rather robustly vindicated of any ill effects. Still others, like lauric acid predominant in coconut oil, remain the focus of unresolved scrutiny, with the jury leaning toward exoneration. In no case, however, has saturated fat been decisively linked to health benefit.

In the aggregate, then, the contentious discourse on saturated fat demonstrates the signature peril of unending debate, and its Newtonian cadence: for every argument, an equal and opposite counter-argument. Lost in the cacophony of such exchange is a temperate truth in the middle: not all saturated fat is created equal; not all saturated fats are harmful; none to date is convincingly beneficial. Much, predictably, depends on dietary context, and specific food choices.

Much the same is true, albeit in the opposite direction, of unsaturated oils. This family of compounds is even larger, and more diverse, encompassing both monounsaturated and polyunsaturated oils. The former, the predominant fat type in olive oil, is indelibly linked to the health-promoting Mediterranean diet, and has been identified among the “active ingredients“ of that diet, responsible for its salutary effects.

The latter group, polyunsaturated fats, is home to the only fats we truly need: essential fatty acids. Those, in turn, come in several varieties, the best known referred to as omega-6 and omega-3 fats. Predictably, much noise has been made about both. The prevailing intake of omega-6 fat in modern diets tends toward excess, resulting in at times exaggerated claims of attendant harms. Intake of omega-3 fats tends toward deficiency, resulting in comparably exaggerated claims of benefit. The reality is that these fats exert favorable effects in a balance best achieved by a sensible diet of wholesome foods.

As with so much else about nutrition, the truth about fat is a bit more nuanced than the dumbed down, hyped up assertions that all too often prevail would suggest. There is no real evidence that any benefit results from restricting total dietary fat intake per se, but on the other hand, most real-world dietary patterns associated with good health outcomes fall within a rather temperate range of total dietary fat. Reducing our intake of saturated fat has not produced the health benefits expected, but this is almost certainly due more to what we started eating instead, and less because saturated fat was mischaracterized. Certain oils, and the foods in which they are native, are clearly health promoting. Certain fats, notably trans fat, are decisively harmful. There is good, bad, and ugly in the mix. Much as we seem to wish for black and white truths on the topic, there are shades of gray.

There are four principal reasons decades of debate about dietary fats have done more to undermine understanding than advance it:
1) We have routinely conflated baby and bathwater.
When adverse effects of certain high-fat diets were observed, we somehow listed toward a focus on cutting fats wholesale. The result, utterly benighted in retrospect, was to embrace low-fat foods no matter their composition, while banishing from our diets all high-fat foods, some of which, notably nuts, seeds, and fatty fish are clearly linked to health benefit.

2) We gave away the Keys to the kingdom.
Leaving aside the divergent opinions about the career and contributions of Ancel Keys, we may reliably accept that he never recommended Snackwell cookies. When Keys and others first recommended we reduce our intake of dietary fat, low-fat cookies and junk food had not yet been invented. They were, in fact, invented in response to the recommendation. The result was that a message born of epidemiology was coopted by Big Food, and converted into something never intended. We never replaced sausage with spinach; we started eating Snackwells with a misguided sense of impunity.

3) We failed to learn from the follies of history.

4) We gave everyone a megaphone.
With the advent of cyberspace and the blogosphere, we gave everyone a megaphone. That took a diversity of opinions, some expert and some clearly not, and turned them into an endless cacophony of echoes. We've created a situation in which it is very hard to discern any reliable signal above the volume of static we produce.

To the extent a debate is about both sides making competing noise, its consummation after all these years may depend on relative quiet. The 2015 Dietary Guidelines Advisory Committee wisely chose to deemphasize nutrients, and instead to emphasize foods. A diet of wholesome foods in sensible combinations, predominantly plants, reliably sorts out fat intake along with all other nutrients. Focus on any given nutrient, and the resulting foods and dietary pattern are as apt to turn out badly as well; more so, if history is reliably indicative.

Some of the best foods for health,vegetables, fruits, beans, lentils, are natively low in fat. Some, nuts, seeds, avocado, salmon, are quite high in fat. Some of the world's best diets are quite low in fat, others quite a bit higher. What they share is a focus on food, not too much, mostly plants.

The cap on dietary fat has, indeed, long outlived any utility it ever had. So, too, has a big, fat debate that has diverted us for far too long to nutrients, from the foods that would be a far more constructive, and healthy focus.

Fat-Savvy Check List:
Total fat content: The world's longest-lived, healthiest populations have diets that vary widely in total fat content, but in all cases emphasize minimally processed foods, mostly plants. The total fat content of a diet is not a reliable indicator of diet quality; health-promoting diets can be quite low, or rather high, in total fat content.
Unsaturated fat: A balanced intake of unsaturated fats from nuts, seeds, avocado, olives/olive oil, and fish has consistently been associated with health benefits.
Saturated fat: Saturated fat is a diverse class of compounds, some of which may be neutral in their health effects. This class of fat, however, has not been associated with specific health benefits.
Trans fats: With its recent action, the FDA has effectively “banned” trans fat from routine use in the U.S. food supply; these fats will be exiting over the next several years. In the interim, partially hydrogenated oil may still be found in some baked goods, chips, fried foods, refrigerator dough, creamers and margarine. Look for it on ingredient lists, and avoid it.
Recommended eating: The short list of foods most decisively and consistently associated with health benefit includes foods both low (vegetables, fruits, whole grains, beans, legumes) and high (nuts, seeds, olive oil, fish) in fat.
Sources: Katz DL, Meller S. Can we say what diet is best for health? Annu Rev Public Health. 2014;35:83-103; Buettner D. The Blue Zones Solution: Eating and Living Like the World's Healthiest People. National Geographic: 2015; Scientific Report of the 2015 Dietary Guidelines Advisory Committee:; Katz DL, Hu F. Knowing What to Eat, Refusing to Swallow It. The Huffington Post; 7/2/14

David L. Katz, MD, FACP, MPH, FACPM, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his blog at The Huffington Post.

Labels: , , , ,


Post a Comment

Subscribe to Post Comments [Atom]

<< Home

This is a printer-friendly version of this page

Print this page  |  Close the preview




Contact ACP Internist

Send comments to ACP Internist staff at

Blog log

Members of the American College of Physicians contribute posts from their own sites to ACP Internistand ACP Hospitalist. Contributors include:

Albert Fuchs, MD
Albert Fuchs, MD, FACP, graduated from the University of California, Los Angeles School of Medicine, where he also did his internal medicine training. Certified by the American Board of Internal Medicine, Dr. Fuchs spent three years as a full-time faculty member at UCLA School of Medicine before opening his private practice in Beverly Hills in 2000.

And Thus, It Begins
Amanda Xi, ACP Medical Student Member, is a first-year medical student at the OUWB School of Medicine, charter class of 2015, in Rochester, Mich., from which she which chronicles her journey through medical training from day 1 of medical school.

Ira S. Nash, MD, FACP, is the senior vice president and executive director of the North Shore-LIJ Medical Group, and a professor of Cardiology and Population Health at Hofstra North Shore-LIJ School of Medicine. He is Board Certified in Internal Medicine and Cardiovascular Diseases and was in the private practice of cardiology before joining the full-time faculty of Massachusetts General Hospital.

Zackary Berger
Zackary Berger, MD, ACP Member, is a primary care doctor and general internist in the Division of General Internal Medicine at Johns Hopkins. His research interests include doctor-patient communication, bioethics, and systematic reviews.

Controversies in Hospital Infection Prevention
Run by three ACP Fellows, this blog ponders vexing issues in infection prevention and control, inside and outside the hospital. Daniel J Diekema, MD, FACP, practices infectious diseases, clinical microbiology, and hospital epidemiology in Iowa City, Iowa, splitting time between seeing patients with infectious diseases, diagnosing infections in the microbiology laboratory, and trying to prevent infections in the hospital. Michael B. Edmond, MD, FACP, is a hospital epidemiologist in Iowa City, IA, with a focus on understanding why infections occur in the hospital and ways to prevent these infections, and sees patients in the inpatient and outpatient settings. Eli N. Perencevich, MD, ACP Member, is an infectious disease physician and epidemiologist in Iowa City, Iowa, who studies methods to halt the spread of resistant bacteria in our hospitals (including novel ways to get everyone to wash their hands).

db's Medical Rants
Robert M. Centor, MD, FACP, contributes short essays contemplating medicine and the health care system.

Suneel Dhand, MD, ACP Member
Suneel Dhand, MD, ACP Member, is a practicing physician in Massachusetts. He has published numerous articles in clinical medicine, covering a wide range of specialty areas including; pulmonology, cardiology, endocrinology, hematology, and infectious disease. He has also authored chapters in the prestigious "5-Minute Clinical Consult" medical textbook. His other clinical interests include quality improvement, hospital safety, hospital utilization, and the use of technology in health care.

Juliet K. Mavromatis, MD, FACP, provides a conversation about health topics for patients and health professionals.

Dr. Mintz' Blog
Matthew Mintz, MD, FACP, has practiced internal medicine for more than a decade and is an Associate Professor of Medicine at an academic medical center on the East Coast. His time is split between teaching medical students and residents, and caring for patients.

Everything Health
Toni Brayer, MD, FACP, blogs about the rapid changes in science, medicine, health and healing in the 21st century.

Vineet Arora, MD, FACP, is Associate Program Director for the Internal Medicine Residency and Assistant Dean of Scholarship & Discovery at the Pritzker School of Medicine for the University of Chicago. Her education and research focus is on resident duty hours, patient handoffs, medical professionalism, and quality of hospital care. She is also an academic hospitalist.

Glass Hospital
John H. Schumann, MD, FACP, provides transparency on the workings of medical practice and the complexities of hospital care, illuminates the emotional and cognitive aspects of caregiving and decision-making from the perspective of an active primary care physician, and offers behind-the-scenes portraits of hospital sanctums and the people who inhabit them.

Gut Check
Ryan Madanick, MD, ACP Member, is a gastroenterologist at the University of North Carolina School of Medicine, and the Program Director for the GI & Hepatology Fellowship Program. He specializes in diseases of the esophagus, with a strong interest in the diagnosis and treatment of patients who have difficult-to-manage esophageal problems such as refractory GERD, heartburn, and chest pain.

I'm dok
Mike Aref, MD, PhD, FACP, is an academic hospitalist with an interest in basic and clinical science and education, with interests in noninvasive monitoring and diagnostic testing using novel bedside imaging modalities, diagnostic reasoning, medical informatics, new medical education modalities, pre-code/code management, palliative care, patient-physician communication, quality improvement, and quantitative biomedical imaging.

Informatics Professor
William Hersh, MD, FACP, Professor and Chair, Department of Medical Informatics & Clinical Epidemiology, Oregon Health & Science University, posts his thoughts on various topics related to biomedical and health informatics.

David Katz, MD
David L. Katz, MD, MPH, FACP, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care.

Just Oncology
Richard Just, MD, ACP Member, has 36 years in clinical practice of hematology and medical oncology. His blog is a joint publication with Gregg Masters, MPH.

Kevin Pho, MD, ACP Member, offers one of the Web's definitive sites for influential health commentary.

MD Whistleblower
Michael Kirsch, MD, FACP, addresses the joys and challenges of medical practice, including controversies in the doctor-patient relationship, medical ethics and measuring medical quality. When he's not writing, he's performing colonoscopies.

Medical Lessons
Elaine Schattner, MD, FACP, shares her ideas on education, ethics in medicine, health care news and culture. Her views on medicine are informed by her past experiences in caring for patients, as a researcher in cancer immunology, and as a patient who's had breast cancer.

Mired in MedEd
Alexander M. Djuricich, MD, FACP, is the Associate Dean for Continuing Medical Education (CME), and a Program Director in Medicine-Pediatrics at the Indiana University School of Medicine in Indianapolis, where he blogs about medical education.

More Musings
Rob Lamberts, MD, ACP Member, a med-peds and general practice internist, returns with "volume 2" of his personal musings about medicine, life, armadillos and Sasquatch at More Musings (of a Distractible Kind).

David M. Sack, MD, FACP, practices general gastroenterology at a small community hospital in Connecticut. His blog is a series of musings on medicine, medical care, the health care system and medical ethics, in no particular order.

Reflections of a Grady Doctor
Kimberly Manning, MD, FACP, reflects on the personal side of being a doctor in a community hospital in Atlanta.

The Blog of Paul Sufka
Paul Sufka, MD, ACP Member, is a board certified rheumatologist in St. Paul, Minn. He was a chief resident in internal medicine with the University of Minnesota and then completed his fellowship training in rheumatology in June 2011 at the University of Minnesota Department of Rheumatology. His interests include the use of technology in medicine.

Technology in (Medical) Education
Neil Mehta, MBBS, MS, FACP, is interested in use of technology in education, social media and networking, practice management and evidence-based medicine tools, personal information and knowledge management.

Peter A. Lipson, MD
Peter A. Lipson, MD, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. The blog, which has been around in various forms since 2007, offers musings on the intersection of science, medicine, and culture.

Why is American Health Care So Expensive?
Janice Boughton, MD, FACP, practiced internal medicine for 20 years before adopting a career in hospital and primary care medicine as a locum tenens physician. She lives in Idaho when not traveling.

World's Best Site
Daniel Ginsberg, MD, FACP, is an internal medicine physician who has avidly applied computers to medicine since 1986, when he first wrote medically oriented computer programs. He is in practice in Tacoma, Washington.

Other blogs of note:

American Journal of Medicine
Also known as the Green Journal, the American Journal of Medicine publishes original clinical articles of interest to physicians in internal medicine and its subspecialities, both in academia and community-based practice.

Clinical Correlations
A collaborative medical blog started by Neil Shapiro, MD, ACP Member, associate program director at New York University Medical Center's internal medicine residency program. Faculty, residents and students contribute case studies, mystery quizzes, news, commentary and more.

Interact MD
Michael Benjamin, MD, ACP member, doesn't accept industry money so he can create an independent, clinician-reviewed space on the Internet for physicians to report and comment on the medical news of the day.

PLoS Blog
The Public Library of Science's open access materials include a blog.

White Coat Rants
One of the most popular anonymous blogs written by an emergency room physician.

Powered by Blogger

RSS feed