Low Carb vs Low Fat vs Just Eat Less

So many dogmatic claims are flying around about low-carb diets being the weight loss and cardiovascular health panacea.  Almost every diet book in the last few years focuses on some variant of the low-carb diet.  Carbs = bad!  Everyone is jumping on the bandwagon, from journalists, entrepreneurs, celebrities, and other self-proclaimed obesity “experts”.  They present all kinds of hypotheses about the influence of carbohydrates on insulin function and cardiovascular disease risk factors.  I find this puzzling from a clinical and research standpoint—-I watch people go through the weight loss process every single day.  Some fail, some succeed, and the difference between the two never is as simple as whether they have committed to a low-carb or low-fat diet.  In fact, I have seen very few people truly successful at losing weight using a low-carb approach, mostly due to difficulties with adherence.  Balanced diets appear to be the “secret” of successful losers, but don’t take my word for it, the National Weight Control Registry is filled with thousands of successful long-term losers and only 10% purported to have done so via a low-carb approach, all others were low-fat, balanced diets (Phelan et al 2006).  Low-carb dieters were no more or less likely to keep the weight off.  All of that is observational data though, it doesn’t suggest cause-and-effect.

Let’s visit the randomized trial data.  Randomized trials are the ideal research design to demonstrate cause-and-effect because people are randomized to conditions which in most cases controls all differences between the groups besides the intervention itself.  Dr. Michael Dansinger at Tufts University did a study in 2005 when he compared the Atkins (very low-carb), Weight Watchers (low-fat/balanced), Ornish (really low-fat), and Zone (low-carb) diets and examined weight loss and cardiovascular risk factors (blood pressure, cholesterol, insulin, and C-reactive protein) after 1-year (Dansinger et al 2005).   There were no differences between diets.  The only thing that predicted weight loss and improvements in cardiovascular disease risk was adherence to the diet, regardless of condition.

Yesterday, a group at Harvard published a similar trial (de Sousa et al 2012).  They compared 4 different diets varying in nutrient composition on weight loss, fat mass, lean mass, abdominal fat, and liver fat (the latter two of which are very dangerous areas to have excess fat in terms of risk for diabetes and heart disease).  The 4 diets were as follows:  low-fat/average protein, low-fat/high protein, high-fat/average protein, high-fat/high-protein.  All diets were equivalent in terms of the calories (750 cal deficit from energy requirements per day—which is typical for weight loss).  Findings revealed no differences between groups on any outcome and that the only predictor of weight loss was.. wait for it… calorie intake.  People who ate less, lost more weight!  Another finding of the study is that in spite of tight controls and intensive counseling, people asked to eat the high-protein diet (25% protein) on average did not reach the targeted level of protein intake (people averaged 22% protein as compared to 18% protein in the other conditions), thus the difference in protein intake between the groups was not as large as they had planned.  Does this mean the trial failed?  No, it means that even under the best circumstances, it is difficult for people to stick to a high-protein diet.

While these are only two studies, De sousa provides a nice review of this literature in their paper.  To summarize it, there are as many studies that have found an advantage of low-carb diets (on abdominal fat loss only) as there are ones that have not found an advantage, but those that have found the advantage failed to account for important factors when measuring abdominal fat.  At the end of the day, there is no scientific case to make for a low-carb/high protein or any specific diet being any better than just eating less food.  Period.

Why then are all the best-selling diet books peddling low-carb/high-protein diets?  I submitted my book proposal called none-other-than FUdiet to a high-powered publisher in New York City.  He said what exactly is your “diet.”  I said, “I don’t have a “diet,” I help people lose weight.  I have published over 70 studies and book chapters on the topic.  I treat patients for obesity in a hospital. Weight loss is my job.  It’s all I do.  In my experience, weight loss is about behavior, not specially-formulated diets.  I want to write about the behavioral path to successful weight loss.”  He said you need a “diet” or you need to be a “celebrity” to sell a diet book.  Well I have neither, but this exchange revealed a lot about the diet book publishing world.  They want to market a diet, and so diet books are what the consumers get.  I think you can guess what I think of that:  FU diet.

Bottom line:  To lose weight, eat less.

How do you eat less?  Now THAT’S what I can help you with.


Phelan, S., Wyatt, HR, Hill, JO, and Wing, RR (2006). Are the eating and exercise habits of successful habits changing?  Obesity, 14(4), 710-716.

Dansinger, ML and colleagues (2005).  Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: a randomized trial. Journal of the American Medical Association, 293(1), 43-53.

de Sousa, RJ, Bray, GA, and colleagues (2012). Effect of 4 weight loss diets differing in fat, protein, and carbohydrate on fat mass, lean mass, visceral adipose tissue, hepatic fat: Results from the POUNDS trial. American Journal of Clinical Nutrition, epub ahead of print.


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    i wish, SO wish that you could be in my office when my office mate goes off on a tirade about her newest fad diet. for the past two weeks it has been ‘beans and greens’, promoted by some guy who’s name i forgot almost as soon as she mentioned it. she heard about him on the radio and went right out and bought his books.
    in two weeks, she hasn’t lost an ounce.
    before this one, it was high protein, almost no carbs.
    that lasted a month. still, of course, no weight loss.
    i dunno HOW many times i’ve tried to explain to her the whole “burn more than you consume=weight loss, consume more than you burn=weight gain” equation, but she just doesn’t ‘get it’. or refuses to. either one.
    keep up the great work!!!

  2. I absolutely agree with you that weight loss & being healthy overall is very much a behavioral thing. One thing I have difficulty with being a personal trainer is getting people to see healthier living through a behavior change lens. I try to explain and model ways to design for habit change, but it sorta just goes over people’s head. I guess they expect some type of system that does all the thinking for them like P90x, but that really doesn’t create sustainable health positive habits that last a lifetime in my opinion.

    • Sherry says:

      Hi Kevin. I definitely agree that it is a challenge to get clients to see it this way. They are so used to being bombarded by fad diets and novelty programs that they have an appetite for the latest “secret” to this being easier than it is. Like the publisher I mentioned, people want a new solution. I think that real progress begins when you can convince them to give up on that. The secret is that there is no secret. The search for the secret actually takes you further from your goal. Thanks for reading!


  3. Some people have medical conditions that help them to become fat but that is not that frequent. Otherwise the real problem is lack of peace and happiness in their life. They try to fill it with food. The less MPG that a car uses, the cheaper it costs for gas.

    The slower a metabolism, the more efficient and cheaper their cost for food. But people want to eat a lot more food than they need to get happiness out of it. Fat Bastard says that he eats because he is sad and he is sad because he eats so much. So for people to get the food that they need for happiness, they need to take cocaine or vomit up food after they eat it to stay thin. Or they can find happiness another way like yoga or meditation.

  4. Dr. Sherry, To get a book deal you can follow the example of an MD in the late 1800s. He saw the bad effects of medications so he switched to all sugar pills. That way they still had the placebo effect. He told the patients that for the drugs to work, they need to make certain lifestyle changes. The lifestyle changes made the difference.

    So your book can teach them everything that you want to teach them. But you explain that these things help your magic fat burning diet to work. Arizona has the 5 Cs that are on the state flag that are Arizona’s main products– cotton, copper, citrus fruits, cattle and climate.

    So you can have the 5 Cs diet. One day a week, they eat 2 carrots, the next day they eat a cucumber, the next day they eat 2 celery stalks, the next day 2 ounces of red cabbage and the next day they eat 2 ounces of cauliflower. This combination will put their body into an incredible fat burning mode as long as they follow your other suggestions. The book people are saying that you need a gimmick. So create a gimmick.

  5. Dr. Val says:

    Hi Sherry – in general I agree with you and am a big fan of the NWCR. Weight loss can be achieved in many different ways, and it’s more important to find a diet/exercise plan that you can stick to than to stick to a particular one. That being said, there is some evidence that higher protein (higher dairy) diets contribute to a more favorable change in body composition as weight is lost (fat is lost while muscle mass is maintained). See this nice study for example: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3159052/?tool=pubmed

    The limitations of the study are that it only followed the subjects for 4 months, and that they were all pre-menopausal women. However, I think the study does suggest that macronutrient composition can play a role in losing the kind of weight you want (FAT not muscle). There is probably an advantage to strength training with a higher protein/dairy diet for optimal fat loss. I don’t think it’s a panacea (it only works if you stick to it) but it does seem to be a real effect, IMO. 😉

    • Anoop says:

      Yo are right Dr. Val.

      In fact, the recent study by Dr. Bray showed how a high protein group showed great LBM gains compared to the same calories but with lower protein. And there is evidence for maintaining LBM with high protein on a diet too.

      But the question is how much of a clinical significance does this increase in LBM have on maintaining weight loss or losing weight in the long run? I think Dr. Sherry is pointing to that.

    • Please note from my picture that I am a mighty white person and have no problem digesting dairy. But the majority of non-white people cannot digest dairy. All other mammals do not consume milk as adults. As for as non-white I am talking about blacks in Africa and Asians in Asia. Many blacks in America are part white since it was legal to rape black slaves as your property back in the day.

      Also note that cow’s milk has more protein than human breast milk. So if you want milk, then you should breastfeed. Also many problems that Americans have are from too much protein. http://www.pcrm.org/search/?cid=132

      If you look on youtube under “fruitarian dancing” there is a woman dancing that eats 97% raw fruit. Not only that but she eats more fruit than just about anyone. In other words she eats as much fruit as 10 Americans eat (like 50 bananas in a day). She is thin. Plus she has pictures of when she was overweight on a normal diet.

  6. I agree that all things being equal, eating fewer calories will lead to a smaller body weight, more or less, though I wouldn’t give a blank endorsement even of that.
    To me, an issue concurrent to calorie count is whether one’s physiology allows them (or makes it relatively harder or easier) to live happily and prosperously on that lower level of calories.
    My experience, and observation of others’, is that one’s biochemistry must be considered rather than just saying “just eat less.” Not everyone has the same experience from the same caloric intake, or even the same caloric composition.
    Specifically, I have identified flour and processed sugar as substances that lead me to binging. (This isn’t a complete list, but will illustrate.) In addition to needing to have reasonable calorie intake, I have to choose wisely in other ways as well, or I will overeat.
    Is this predetermined? Will it happen every time? No. But I’ve had enough experience to know that it is more complicated than just “calories in, calories out.” That bromide isn’t wrong; it’s just incomplete.
    The term I use to describe my experience is that I’m a food addict.

    • Sherry says:

      Thanks for your comment, Michael. I certainly agree with you. When binge eating and/or food addiction issues come into play, then we need to start looking at specific trigger foods/macronutrients and figuring out how to eliminate those foods from the diet. That can be a tougher row to hoe than just weight loss. Thanks for bringing this perspective!


  7. “low-fat, balanced diets” – Oh dear. What a misleading statement. What exactly is ‘low fat’ and how is it balanced if it is (apparently) under emphasising one of the macro nutrients?

    • Sherry says:

      Thanks for your comment. I’m referring to low-fat diet as they are used in evidence-based weight loss programs such as the Diabetes Prevention Program. This would consist of 30% fat-30%pro-40%carb, which is a pretty balanced diet.

  8. John says:

    “In fact, I have seen very few people truly successful at losing weight using a low-carb approach, mostly due to difficulties with adherence. Balanced diets appear to be the “secret” of successful losers, but don’t take my word for it,”

    You probably have seen few people successful at it because of your subjective view on the topic. Your reference group may be a bit skewed. The excuse of ‘non-adherence’ is flat at best. Essentially, someone can say a diet failed because they lacked the will power. This is not diet failure. Furthermore, low-carbohydrate diet, once the individual is in a ketogenic state, has a remarkably easy adherence due to a rapid change of constant hunger (i.e. low fat or limited calorie diet) to prolonged satiety.

    The truth is, those with “balanced” diets as you say have lost weight because they have cut out refined carbohydrates in some way. Rather than referring back to science for a cause, you are contending the simplistic:

    “Bottom line: To lose weight, eat less.”

    Eating less, i.e. restricting calories I would argue has less adherence. Telling someone they need to be hungry is not a good method. It skips honing in on the fundamental cause of weight gain.

    Lastly, you speak of the diet study and:

    “There were no differences between diets. The only thing that predicted weight loss and improvements in cardiovascular disease risk was adherence to the diet, regardless of condition.”

    A more recent 2007 study from JAMA: http://jama.jamanetwork.com/article.aspx?volume=297&issue=9&page=969, Christopher D. Gardner, PhD; Alexandre Kiazand, MD; Sofiya Alhassan, PhD; Soowon Kim, PhD; Randall S. Stafford, MD, PhD; Raymond R. Balise, PhD; Helena C. Kraemer, PhD; Abby C. King, PhD

    1)HDL, Triglycerides, blood pressure, levels of insulin resistance all improved:

    “Many concerns have been expressed that low-carbohydrate weight-loss diets, high in total and saturated fat, will adversely affect blood lipid levels and cardiovascular risk.34 – 36 These concerns have not been substantiated in recent weight-loss diet trials. The recent trials, like the current study, have consistently reported that triglycerides, HDL-C, blood pressure, and measures of insulin resistance either were not significantly different or were more favorable for the very-low-carbohydrate groups.12 – 16 ”

    2)LDL particle size even changes:

    “The triglyceride-lowering effect of a low-carbohydrate diet leads to an increase in LDL particle size, which is known to decrease LDL atherogenicity.”

    3)Weight Loss better for Atkins style carbohydrate restriction at 2, 6 and 12 months:

    “Compared with women who were assigned to follow diets having higher carbohydrate content, women assigned to the diet with the lowest carbohydrate content had more weight loss and more favorable changes in related metabolic risk factors at 2 and 6 months. The finding of greater weight loss for the Atkins diet continued through 12 months, reaching statistical significance in comparison with the Zone diet.”

  9. This study was seriousy methodologically flawed, therefore it is not possible to make reliable and definitive conclusions that there is no difference between different types of diets. In this reagard I´d like to point out that about 10 years ago Alderson & Chalmers (1) presented evidence that inappropriate claims of no effect or difference occured in about a fifth of abstracts of Cochrane reviews. In my eletter response (2) I mentioned that it is well to remember that claims of “similarity” or “difference” are often made by tests of statistical significance that are often misapplied or accompanied by methodologically flawed experimental design. Confidence intervals provide a useful addition to significance tests. Nevertheless, identifying the best evidence requires detailed appraisal of several additional items(3). This point seems to be more important than concerns for careless wording
    1. Anderson P, Chalmers I. Survey of claims of no effect in abstracts
    of Cochrane reviews. BMJ 2003;326:475.
    2. http://www.bmj.com/content/326/7387/475?tab=responses
    3. Barton S. Which clinical studies provide the best evidence? The
    best RCT still trumps the best observational study. BMJ 2000;321:255-

  10. Julie says:

    In the end, I do think calorie intake certainly has something to do with it, but being content with your diet (way of eating for life) is what really matters, especially if it works for you. Of course, real food (not processed) is better. I have found the reason low carb works for me is that I LIKE this way of eating, I am not hungry, so in the end I probably do eat less. But I don’t have to worry about eating less or counting calories, etc. And occasionally I eat a teaspoon or less of something sweet at a party, and am satisfied. I set out to do my own version of low carb last October, and it works well. I am losing very slowly (and am probably where I’m going to stay unless I eat less) because I didn’t give up alcohol, and am eating a lot of nuts, etc. So that is what works for me. It didn’t feel like a diet. That is the key. Also, I really believe good fats, protein, and veges are all we really need to be healthy. There is no requirement in my body for grains, but fats and proteins are essential. I’m almost 55, active, and this is how I am going to eat forever. I feel committed, not bloated, and happy. To each their own, but eating high quality food should be part of that.

  11. Dr. Pagoto
    You hit the nail on the head. I love the science! There is a fundamental problem about low carb diets, is that we don’t live in a low carb world. When someone comes over to my house I am going to offer them a carbohydrate at the door, not a protein. Low carbohydrate diets remove us from our current environment, then we are placed back into them; weight regain is inevitable. We need to learn how to eat carbohydrate and lose weight at the same time. Carbohydrates aren’t the issue, eating too many of them are, but we don’t need to eliminate them to see change. Thank you for your attention to the science world! FUdiet!

    • Sherry says:

      Thanks for your comment Jason. You said it best, “we don’t live in a low-carb world.” I do believe that the best diet is the one that you have the easiest time sticking to, and that will vary across individuals. Not a one-size-fits-all… then again, nothing is!


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