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

Wednesday, October 15, 2014

A comparison of low carb and low fat diets

The joys of September! Parents gleefully shove their reluctant children onto school buses, the palm trees in Los Angeles don’t change color, and everyone realizes that they gained 20 pounds during their summer vacation. It’s time to get serious again about losing weight.

But how should you eat to best help you shed the extra pounds? Many people are passionate about their favorite diet, but there is very little data comparing different diets to each other. Some swear by low carbohydrate diets (like Atkins), while others insist that low fat diets (like Weight Watchers and others) yield more weight loss and achieve healthier cholesterol numbers.

A study published in Annals of Internal Medicine attempted to shed some light on this question. The study enrolled 148 men and women who were obese (BMI 30 to 45) but didn’t have diabetes or cardiovascular disease. The participants were randomized into 2 groups. One group was counseled to eat a low carbohydrate diet, with less than 40 grams of carbohydrates per day. The second group was counseled to eat a low fat diet, with less than 30% of total calories from fat, and less than 7% from saturated fat. Neither group was counseled about limiting total calories or about exercise. Both groups received ongoing periodic dietary counseling throughout the study.

The subjects were followed for a year and had periodic assessments of their weight, diet, cholesterol, blood pressure, and other blood tests measuring cardiovascular risks.

At the end of the study the group eating a low fat diet lost an average of 4 lbs. while the group eating a low carbohydrate diet lost an average of 12 lbs. Even more impressive was that the low-fat group lost lean body mass (muscle weight) and gained fat weight, while the low-carbohydrate group lost fat weight and gained muscle. This is especially surprising since average caloric intake and physical activity was similar between groups. One frequent criticism of low carbohydrate diets, that it results in an increase of LDL (bad cholesterol), was dispelled. Total cholesterol and LDL levels remained similar between groups, but the low-carbohydrate group had bigger increases of HDL (good cholesterol).

This all suggests that a low carbohydrate diet leads to more weight loss than a low fat diet while improving body fat composition and some cholesterol measures. For those who are losing weight on a low carbohydrate diet but were worried that the excess fat intake was increasing their cardiovascular risk, this is good news.

Though the results were trumpeted as a major vindication for low carbohydrate diets, I interpret the results differently. Sure, the low carbohydrate group fared better than the low fat group, but what I find striking is how disappointingly modest the results in both groups were. The participants had a BMI of 30 to 45 which means that at minimum they were 35 pounds overweight, some much more. An average weight loss of 12 lbs. is a laudable step in the right direction but is a small fraction of the weight that should be lost. Considering the fact that this weight loss took 12 months and that all longer term studies suggest that some of this lost weight will be regained, the results seem quite discouraging.

So I conclude from this study that any diet that helps you eat less and that you can maintain indefinitely will help you lose weight but that for meaningful weight loss you have to make a more radical change in your diet than the groups in this week’s study. If you feel full and not deprived on a low carbohydrate diet, then do it and stick to it. But you should probably have even less carbohydrates than 40 gm per day until you reach your target weight. This study at least reassures you that your cholesterol and body fat composition won’t get worse. If you do best with a low fat diet, consider a diet that is radically low in fat, like a plant-based vegan diet without processed foods. My patients who have stuck with either strategy have done well. This study is also a reminder that without exercise, changing what you eat will only achieve modest results. Frequent exercise can accelerate weight loss while maintaining muscle mass.

And for people who are over 100 lbs. overweight, especially those with diabetes, studies increasingly suggest that weight loss surgery has healthier outcomes than diet and exercise alone.

So let’s all make a plan and get started. Thanksgiving is just around the corner.

Learn more:
A Call for a Low-Carb Diet That Embraces Fat (New York Times)
Cutting Back On Carbs, Not Fat, May Lead To More Weight Loss (NPR)
Effects of Low-Carbohydrate and Low-Fat Diets: A Randomized Trial(Annals of Internal Medicine)

Some of my past posts on diet and weight loss:
Why Losing Weight Is So Hard
Startling Scientific Finding: Dieting Leads to Weight Loss
Scientifically Proven Weight Loss Method: Eat Less

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. Holding privileges at Cedars-Sinai Medical Center, he is also an assistant clinical professor at UCLA's Department of Medicine. This post originally appeared at his blog.

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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.

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