New major study: A calorie is not a calorie

low-carb better for weight maintenance

Despite what the sugary beverage and processed snack food companies want us to believe, all calories are not created equal.

A new study from Harvard shows that individuals following a low-carbohydrate (20% of total calories) diet burn between 209 and 278 more calories per day than those on a high-carbohydrate (60% of total calories) diet. So the type of calories we eat really does matter.

The New York Times: How a low-carb diet might help you maintain a healthy weight

This isn’t the first study to investigate this topic, but it is likely the best.

The current study was a meticulously controlled, randomized trial, lasting 20 weeks. Even more impressive, the study group provided all the food for participants, over 100,000 meals and snacks costing $12 million for the entire study! This eliminated an important variable in nutrition studies — did the subjects actually comply with the diet — and shows the power of philanthropy and partnerships in supporting high-quality science.

After a run-in period where all subjects lost the same amount of weight, participants were randomized to one of three diets: 20% carbs, 40% carb, or 60% carbs, with the protein remaining fixed at 20%. Importantly, calories were adjusted to stabilize weight and halt further weight loss, thus making it much more likely that any observed difference in calorie expenditure was not from weight loss, but rather from the types of food consumed.

After five months, those on the low-carb diet increased their resting energy expenditure by over 200 calories per day, whereas the high-carb group initially decreased their resting energy expenditure, exposing a clear difference between the groups. In addition, those who had the highest baseline insulin levels saw an even more impressive 308-calorie increase on the low-carb diet, suggesting a subset that may benefit even more from carbohydrate restriction.

Why is this important? It shows why the conventional wisdom to eat less, move more and count your calories is not the best path to weight loss. Numerous studies show better weight loss with low-carb diets compared to low-fat diets, and now studies like this one help us understand why.

Our bodies are not simple calorimeters keeping track of how much we eat and how much we burn. Instead, we have intricate hormonal responses to the types of food we eat. It’s time to accept this and get rid of the outdated calories in-calories, calories-out model, thus allowing for more effective and sustainable long-term weight loss.

Additional coverage of this dramatic new study:

LA Times: The case against carbohydrates gets stronger (by study author Dr. David Ludwig)

The Times: Low-carb dieters “shed more weight”

MedPage Today: Low-carb diet wins for weight maintenance


Cutting calories won’t solve your weight issues – do this instead

Is low carb the best treatment for reversing diabetes?


A low-carb diet for beginners

How to lose weight

Weight loss



  1. 1 comment removed
  2. Eileen
    Thank-you, too many people have made calorie-counting a religion. Some now make low carb a religion. Why can't we just stick with the facts? I know that calorie-counting failed me big time, but low carb saved my life. Not everyone can eat what I eat, and I cannot eat what other low-carbers eat, but that's the beauty of the variety we enjoy in modern times. This site has been excellent for letting us choose the low-carb path that suits the individual. Also, I really enjoy the science/medical articles you post.
  3. Dr. Bret Scher, MD Team Diet Doctor
    Thanks Eileen! I really like your perspective on this. I wish more people thought like you do. Thanks for your comments!
  4. Sally
    I started Low Carb eating to see if it would help me with the symptoms of ME (myalgic encephalomyelitis). Sadly, Low Carb is no cure for ME, but my symptoms abated somewhat, so I stuck with it.

    Low Carb is helping me in another way though. Having gained a few pounds due to my illness-induced sedentary lifestyle, I am now pleased to note the scales gradually dropping back to a healthy weight for my height. I wasn’t really expecting to loose weight, because I was eating LC to satiety, and thinking only of making the transition to the new way of eating. Yet there it is, I am down about 18lbs in 7 months, bringing my BMI to 24.

    This is so simple. No need to count calories. No feelings of hunger, or deprivation. And after the first few adjustment weeks, I’ve no urge to eat sweet stuff. I never thought I would become so relaxed about turning down desserts!

    Another thing. Before LC, I always really felt the cold. Now I’m eating LC, this is much less of an issue. Perhaps that increased metabolism mentioned in the article accounts for my new found warmth? Lots to think about, but I’m sure happy to keep eating this way.

    Thanks Diet Doctor. :)

  5. Nate
    This study is great news. The LCHF diet is slowly getting the recognition that it deserves. Unfortunately, I read the comments at the end of the New York Times article and saw most people still think the diet cannot work long term or gives one heart or cancer problems. We still have a long way to go to change the damage done by "scientists" using bad science, opinion, corporate selling points (lies?), or just wishful thinking to give dietary advise.
  6. Karen
    Thank you! Great article.
  7. Claudia
    If only my teachers would accept the progress in science. But no, the Dietary guideline is the Bible and you‘ve to eat around 55% of carbs a day. And yes, a calorie is a calorie. Period! It’s like a relegion for them. In 2022 I‘ll finally call myself a nutritional therapist and I’m pretty sure until then the case against carbs / sugar just gets stronger and stronger. It‘s kind of a weird experience to learn outdated stuff and to recall it correctly at the exam, even you know better. But that’s just how it is. Patience is key and nobody as myself is in charge of what to put into my mouth. At least ... I’m free.
    Reply: #10
  8. Greg Hill
    I've been saying for a long time that the entire concept of counting calories is just plain nonsense, because of the enormous differences between the way the number of "calories" in foods are measured in scientific laboratory experiments, and the way in which our bodies actually process those foods. For example, a molecule of fat can potentially be "burned" as a source of energy by my body, in which case the number of calories it contains is a useful value. But what if that same molecule is used instead as part of a cell wall? In that case it contributes absolutely nothing to my effective energy intake and logically, therefore, should not be counted as a source of "calories" at all. A similar observation could be made of protein, which of course can be "burned" as a source of energy if need be, but most of the time is used in probably thousands of different ways which -- including in the calculation, as is almost never done, the higher energy cost of simply digesting it -- may ultimately cause more calories to be burned in its utilization than it is said to contain as a potential source of energy. But for some reason nobody ever seems to even mention that. A "calorie" in food counts as a calorie in our metabolism only if we end up either using it directly and immediately as a source of energy or storing it as fat to be used as a source of energy at some time in the future.

    Although certainly interesting, the results of a study like the one reported here are woefully incomplete. We loose a lot information when we treat all members of a group as being physiologically equal to their statically computed "average" member. We could learn so much more from a similar (albeit three times as expensive to run) study that observed every subject under all three test conditions. We almost certainly would find that some individuals would fare better in each of the three test conditions than in the other two, especially if we were measuring more than simply the number of calories "burned" and assessed other quality of life and health measures such as their motivation to get physical exercise, their mental acuity (as opposed to "brain fog"), and their levels of chronic pain.

    Also, besides a "calorie" not necessarily being a true calorie in terms of its energy contribution, I think we also would need to look more closely at the fact that "a calorie from carbs" is not just "a calorie from carbs." It also varies a lot according to the type of carbs (e.g. simple/refined vs. complex, or glucose vs. fructose which are metabolized entirely differently) not only in terms of how our bodies process and utilize them, but also in terms of how they affect our gut microbiome.

    The bottom line is, rather than just blindly following the "dictates" of some kind of "scientific" finding in terms of what constitutes a healthy diet, each of us ultimately really needs to experiment around and find out what kind of diet works best for ourselves as unique individuals.

  9. Aleksejs
    The "calorie is not a calorie" really starts to drive me nuts. Calorie is a calorie.
    Different foods affect differently how body utilizes fats, carbs and protein.
    By eating high processed carb diet you get fatter because more calories is stored because more insulin is released, compare to whole food low carb diet. Not because "calorie is not a calorie".
    Our bodies are very complex system. Counting calories from food we consume and then use some empirical number to multiply with our body weight to analyze the energy flow in our bodies is way to simplistic, especially for obese sick people, who's metabolism is really damaged.
    As far as i know from google and every nutrition plan/guides, all the presentations i saw on these website and youtube channels, it says that fat and carbs are mainly used as energy source, but protein is mainly used to build muscles and other body parts.
    Then question is: Why do people count the protein they eat as calories consumed (4 kcal/g), when its used as building material?
    In Dr. Ted Naiman's "Too much protein is better than too little" presentation you can see that people who ate more protein lost more weight compare to lower protein diet (diets were "isocaloric"). According to basics of fats, carbs and protein knowledge these diets are not isocaloric, unless you burn them in fire, but as we know protein is not burned for energy primary in human body, but rather is used as building material. So people, who ate the higher protein diet, ate less energy, a.k.a. calories (carbs and fats), and to get energy for body needs they burned stored energy (aka mainly stored body fat), thus leading to bigger weight loss. This makes more sense (thou this is just my thoughts just using logic and the knowledge i have), than saying "calorie is not a calorie", which doesnt tell anything how our body works.
    Replies: #12, #13
  10. Candy Lind
    Claudia, maybe you’re destined to present a Doctoral Dissertation that contests or refutes all the dogma you’re having to choke down. Stand strong! Question Authority! 👍🏻
  11. Leonie Johnston
    Claudia, us diabetics need nutritional therapists like you. I have a constant battle in South Australia trying to find a nutritionist who knows as much about LCHF as I do ;a retired teacher with no medical background other than my own health issues - I’ve been type 1 for 34 years and on a pump for 6 years. With a Diabetic Association so far behind the most recent findings, I’m left to fly solo, with the help of Diet Doctor & similar sites. It’s disgaceful and all diabetics deserve better. So many with type 2 could get off all their medication as well as leading healthier lives.
  12. Greg Hill
    Aleksejs, you and I obviously share the same basic beliefs about all this. (Please see my earlier comment.) We just choose to use language to talk about it differently. When I hear the words "a calorie is a calorie," I assume that what the person saying that really means is "a potential calorie eaten can only be either burned as a source of energy or stored as fat." They simply don't understand the scientific facts as you have (clearly and, I believe, correctly) explained them in your comment. You, I, and Drs. Scher and Ludwig apparently all agree about all of that.

    One way of countering the assertion that "a calorie is a calorie," meaning that potential calories eaten has to equal calories either burned or stored as fat, would be to say, "No, that's simply not true." But using casual English language in a conversation it's easy for me to mean just exactly that and nothing more by saying "No, a calorie is NOT a calorie." Of course a calorie as defined by physics is a calorie as defined by physics. But when you hear the words "a calorie is not a calorie" your mind apparently represents that statement in what I believe is too literal a sense. When I hear those same words, my mind just automatically skips over the unintended literal interpretation and goes directly to the intended meaning of it, much like what happens when I hear someone unintentionally or even intentionally use a malapropism. If I notice it at all I just get a quick chuckle out of it and move on. We are just using casual conversational English here, which often is not as strict as what would be expected in a peer-reviewed journal article. We are a growing community of people from all walks of life and levels of education, and our goal is to share information and ideas in ways that pretty much anyone can understand, without quibbling over each other's exact choice of words.

  13. Alicia
    Aleksejs, I agree with you. The saying "a calorie is not a calorie" should only be used in immediate response to someone saying "a calorie is a calorie", otherwise it's out of context and meaningless. I prefer the more meaningful expression "it's not about the calories". The unfortunate focus on the energy content of foods for weight control seems to cause low carbers to spend more time refuting this than explaining the carbohydrate-insulin theory of why we gain weight. It's not until someone has an understanding of the impact of carbohydrate on hormones and the impact of those hormones on fuel storage and release, that they can replace the old model of why we get fat with the new model. I like to say that high insulin levels create a one-way door to allow fuels to be stored in cells but not get out again, and it's not until insulin levels fall, that a 2-way door is restored and fat/fuel can flow out of cells to be used. Thanks, Jason Fung, for creating this simple visual metaphor that anyone can understand.
  14. Emily Lovell
    I wish people would just try low carb. Just give it a try before you knock it.
    I also have always had suspicion since I was in highschool that big food companies and big agriculture somehow influenced the food chart/pyamid.
  15. Jonathan
    Another poorly designed study demonizing carbohydrates. Deep sigh.
    Reply: #16
  16. Valeria

    Another poorly designed study demonizing carbohydrates. Deep sigh.

    Explain why you think the study is poorly designed. Explain how you think the study would be precise and accurate. Explain the conclusion you take away from the data gathered in this study and why it doesn't prove it's hypothesis.

  17. Debra
    My nephew and I have both reversed our Type II diabetes, and now my sister, who has been diabetics for many years, is asking us questions with great interest. That's the whole point of these studies, and this get the word out and to educate as many people as we can. The non-scientific explanations are essential for people like my sister who have limited science education. Thank you Diet Doctor. You may save my entire family!
  18. Zoe
    I've known for a long time now learning for myself that "it's not about the calories, but the quality of the food". I've been on low-carb for 2 years now and I have maintained my weight ever since and kept it off (no change on the scales at all). I'm pretty small, only 4'11 and now weigh 45kg's. I was 60kg's before and it was not healthy. I was always eating the standard high-carb high-sugar diet that convectional way. I decided to learn for myself if there was an alternative way to maintain my weight. Upon looking, I discovered HFLC. It changed my life for the better. I've stopped eating sugar immensely, because I discovered that it also ages you (I'm a weight and appearance freak so I care). HFLC has changed me for the better. I no longer treat weight loss for the short term and i feel better than ever. Amazing diet, or maybe you can't call this a diet. In fact it's a "Fixing the biochemistry diet" Or "Working with the body upon fixing yourself" Amazing I feel so much more upbeat and I'll continue to live this way for many years to come!!!!
  19. Rebekka
    There is a lot of talk about this on Instagram, to me it looks like a massive campaign against this knowledge, hammering ferociously that a calorie is a calorie, no matter what. The people who post and comment act very strange, as if ready to defend that statement with their lives. Is this not propaganda? If a few people think that, fine, let them think that, but this looks like an organised campaign, tons of posts, anyone who challenges this or comments the opposite gets attacked and bullied, trying to shut down anyone who does not agree. From looking at several posts like this I don't think his is not a coincidence, someone is behind this, organising this. How can this be stopped? You can always report posts on Instagram, but you can not report something as misleading any more, you only have the option of "I simply don't like it" or reporting that someone is committing an actual crime. It's very frustrating.
  20. 1 comment removed
  21. Nidal
    The most recent study up to my knowledge was published in JAMA. There was no significant difference in weight loss between low-fat and low-carbohydrate diet. That basically means a calorie is a calorie. Theoretically, I agree with the idea that we should not count protein when we count calories. Although in vitro 1g equals 4 calories, but in vivo we do not burn protein. We burn carbs then fat.
  22. 2 comments removed
  23. Andrew Graham
    Not a metabolic ward study, no total control on calories consumed.
    Study is interesting however results do not mean either diet plan was superior.

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