Did a low-fat diet result in more fat loss?


It’s a never-ending debate. Should you avoid carbs or avoid fat to lose weight? The media loves it.

Unfortunately in later years there’s been many many scientific trials showing a clear winner: low carb results in statistically significantly more weight loss. It’s been shown in more than 20 human studies ranging from 3 to 24 months of duration (list of 18 of the studies). A low-fat diet has won a total of 0 (zero) such studies… so the excitement was sort of waning.

But then a small study this week seemed to show the opposite and the media went crazy over it:

BBC: Low-fat diets ‘better than cutting carbs’ for weight loss

The excitement seems a bit misplaced for at least two reasons. To start with, as a sort of side note, the low-fat diet actually resulted in less weight loss (1.3 kilos compared to 1.85 kilos on low carb). So the “better weight loss” part seems at least up for debate.

Confused? Well there’s an explanation.

More Fat Loss

The low-fat diet actually resulted in more fat loss. According to one measurement in the paper a loss of 0.588 kilos (1.3 pounds) of fat compared to a loss of 0.529 kilos (1.2 pounds) in the low-carb group. So the low-carb group lost more weight (presumably more glycogen and water) while the low-fat group lost more body fat.

The two big problem with this study?

  1. First, it was only six days long!
  2. Second, it was conducted in a locked ward, meaning the participants could only eat the food they were served. Thus the reduced appetite on a low-carb diet (the key advantage) was artificially removed as a factor.

What Happens After the 6 Days?

I actually think these results are perfectly accurate. If you cut carbs the body will continue to burn your body’s stored carbs in the first few days, while it adapts and ramps up the fat burning. Importantly this is only temporary as the body’s supply of carbs is very small and will only last a few days, like six days or so… hmmm…

If you instead cut out the fat from your diet, well the body will have to immediately start using the fat reserves.

The problem is what happens AFTER six days. Here’s a hint from the study, here’s what happened to the participants’ fat burning:

In the blue reduced carb (RC) group fat burning is going up like crazy. In the red reduced fat (RF) group the fat burning is actually decreasing slightly, even though they are on a semi-starvation diet.

So here’s the situation after six days in the two groups:

  • The low-fat group has lost slightly more body fat but at the same time reduced their fat-burning capacity.
  • The low-carb group has lost more weight and more glycogen but slightly less body fat. However their fat burning is speeding up a lot (and their glycogen stores are getting low) so it’s time to really burn the fat.


So there we have it. The low-fat group is slightly ahead after six days, when it comes to body fat, but they are burning fat much slower.

The low-carb group is just behind, moving much faster.

Who will you bet on long-term (meaning 3-24 months) when it comes to weight loss? As low-carb has won 20+ studies and low-fat 0 (zero) studies in that time frame I know where I’d place my bet.


New Major Study: A Low-Carb Diet Yet Again Best for Both Weight and Health Markers!

Swedish Expert Committee: A Low-Carb Diet Most Effective for Weight Loss


Of course it’s debatable whether this really was a “low-carb” diet at all, as the diet contained as much as 140 grams of carbs per day. But let’s not even get into that for now.


  1. Walter
    Did someone just waste a few million dollars to call out Gary Taubes?

    Here's my problem with the study:

    - the pool of people is all fairly healthy - no diabetes, not insulin resistant, lipids are good, insulin levels are decent too.
    - the low fat level is about 8% - that's literally a tablespoon of butter and no more fat rest of the day.
    - if low fat is less than 10% fat why isn't low carb less than 10%?

    The classic definition of "low carb" comes from Atkins so this should have been 20grams of carbs for 2 weeks and then 50grams.

    I say this not at all convinced that Taubes is right about insulin driving obesity. I think low carb diets work so well because they supress appetite, drop water quickly and protein is highly thermic.

    What a waste of money.

  2. PaleoLC
    Hej Andreas!

    You have seen that the "LowCarb" group had 140g of carbohydrates per day. Not LowCarb in my world.


    Reply: #3
  3. Dr. Andreas Eenfeldt, MD Team Diet Doctor
    Yes I saw that, it's under "PS" at the bottom of the post. It's not very low carb, no.
  4. charles grashow

    What you FAIL to mention is this

    "In the long term, there are no differences in the effect on weight loss between advice on strict and moderate low carbohydrate diets, low fat diets, high protein diets,
    Mediterranean diets, diets aimed at achieving a low glycaemic load or diets containing a high percentage of monounsaturated fats."

    Replies: #10, #17
  5. Bob Niland
    The fats in the not-really low-carb diet are not adequately identified. Which PUFAs? They claim 2.9 grams of n3, but don't break that down by ALA, DHA and EPA, which is not unsurprising, given the incompetence in the rest of the effort.

    This looks very much like the anointed are running deliberately sabotaged trials to forestall having to apologize, for a few more years, for 40 years of failed and fatal dietary policy.

    Expect exactly zero of the breathless pop news headlines or stories to mention that inconvenient matter of six days.

  6. tz
    What debate?
    Only be carefully constructing biased experiments can they show cutting fat does much.
    Cutting Carbs has been shown effective for three centuries.
    There was no "never ending debate", the science was settled until the late 20th century when they promoted pseudoscience.

    I often hear criticisms of "holistic medicine", but that at least might be wrong or right, but the medical consensus was so wrong, stupid, evil to be pseudoscience on the level of phrenology.

  7. Shannon
    Thanks for the clarification , what a stupid study and a waste of time and money!
  8. Arthur H
    I believe we waste our time trying to debate with people on low fat/high carb diets. It is a well known fact that our brains need 25% of our bodies cholesterol, that being the case, these people would be cholesterol deficient in the brain department. A wise man once told me that it is futile to try and have an intellectual debate with an unarmed adversary !
  9. Peter
    I suspect this little "study" was sponsored by Coca Cola. :-)
  10. Dr. Andreas Eenfeldt, MD Team Diet Doctor
    That's an expected result of falling compliance in all diet groups in these trials.

    According to Occam's razor there's no need to try to invent another cause:

  11. Rachel
    I saw this on an Australian morning show, extremely short segment with no detail. I just rolled my eyes and tucked into my bacon and eggs ?
  12. Ellot
    I am wondering if the National Institute of Diabetes and Digestive and Kidney Diseases, which sponsored this study, has some kind of vested interest. Certainly they are on the saturated fat is bad train, but anything else?
  13. BobM
    I like the crossover design. Other than that, there's not much to like. I'd have preferred seeing a month at least on each diet (you can't adjust to fat burning for 2+ weeks), unrestricted calories, and less than 50 grams per day of carbs for low carb. Of course, the low carb diet would've won, so perhaps that's why they made this so poorly designed.
  14. smc
    Of course this study is complete garbage, for the variety of reasons pointed out above. But that doesn't matter. The media has gotten the headline that it wanted. For years we'll be hearing about the "recent studies" that showed low-carb diets to be inferior. Science doesn't seem to matter these days, only sound-bites.
  15. smc
    I particularly like the statement in the article that states "...the study had 'debunked' many of the claims that low-carbohydrate diets were better...". The authors of this study should be drummed out of any honest professional society to which they now belong.
  16. Ansive
    Could someone explain the Fat Oxidation chart?

    I'm counting about 2800 calories in the 6 days of the study. Dividing by 9 yields 310g of fat oxidized in 6 days.

    Problem 1: I'm not getting the quoted 529g of fat loss.
    Problem 2: How did the low fat group lose more fat in the first 6 days if they oxidized less fat than the low carb group?

    Am I reading the chart completely wrong? (maybe it's just burned fat, which is then offset by ingested fat, or maybe I don't understand the 0 kcal level chart reference)

    Reply: #29
  17. Murray
    Suppose one half of the population are round holes and one half are square holes. Then round pegs and square pegs are randomly distributed among the population. About one half the round pegs fit and one half of the square pegs fit. Committee conclusion: peg selection makes no difference.

    My conclusion: don't entrust your health to committees.

  18. Zepp
    Did a low fat diet beat a low carb diet for fat loss?

    Weight loss vs. fat loss

    The headline could also have been “reduced carb dieters lost 46% more weight than low fat dieters”. This was a finding of the study – the average weight loss with the reduced carb diet was 1.9kg in 6 days; the average weight loss with the low fat diet was 1.3kg in 6 days – that’s a difference of 46% if you want to play the misleading relative numbers again. A genuinely low carb diet (under 10% carb intake) could have achieved a 2-3kg loss in 24 hours, as approximately 500g of glycogen would have been depleted and approximately 2kg of water along with it.


  19. BobM
    After reading the study more closely, I have no idea what this studies proves or disproves. Apparently, they wanted to replace the same amount of calories for fat or for carbohydrate. If they wanted to decrease the calories further, they would not have been able to exclusively reduce only fat or carbs without also affecting protein (and/or fat):

    "Given the composition of the baseline diet, it was not possible to design an isocaloric very low-carbohydrate diet without also adding fat or protein. We decided against such an approach due to the difficulty in attributing any observed effects of the diet to the reduction in carbohydrate as opposed to the addition of fat or protein."

    So, they never really tested a low carbohydrate diet.

    Yet they make comments like:

    "Furthermore, we can definitively reject the claim that carbohydrate restriction is required for body fat loss (Taubes, 2011)."

    I've read both of Taubes's books multiple times. I don't remember him ever stating this. I think even Taubes would agree that one can reduce calories (even fat calories) and still lose bodyfat (at least initially).

    I think it's an interesting experimental design, as they're attempting to change only one variable at a time (though they're changing both calories and fat or calories and carbs, so it's really two variables). It's just the study design does not have much bearing on reality.

    To me, it seems almost like they take issue with what Taubes has said, and they went gunning for him. They designed a study (and got the results they wanted) simply to "disprove" the "carbohydrates are bad" theories such as those proposed by Taubes. Unfortunately for them, the study design was so restrictive that it doesn't really prove or disprove anything. That is, the study was for a certain set of conditions that wouldn't exist in the real world (people going on a low carb diet would not only decrease their carb content, but also reduce their calorie content more than this study provided for, and possibly change other variables such as protein too).

  20. Almira
    But, isn't it great though? I mean... you can go 'almost' low carb and lose body fat, although a little fewer than Very Strictly Low Fat--that I doubt anybody can follow it in long term
  21. Guido Vogel
    Though I agree with many of the comments here, isn't true that the study demonstrated that you CAN lose fat without cutting carbs?

    In a 30% calorie restriction with extreme low-fat (7.7%) and baseline carbs (29%) fat is burnt, weight is lost and insulin goes down.

    If so, what is the metabolic pathway? Either via
    1) Reduced insulin secretion or
    2) Another metabolic pathway
    3) Combination of 1) & 2)

    What are your thoughts Andreas?

    Replies: #22, #23
  22. murray
    The study makes two important claims. First, that it is possible to lose body fat without reducing carbs. That seems to be established, if the control diet has enough fat to make it possible to run a calorific deficit by reducing just the fat and nothing else.

    Note this says nothing about how one got fat in the first place. That required elevated insulin. In my personal experience, eating excess fat alone does not do that and I can eat 3000+ surplus calories of fat per day and not gain any body fat. Sam Feltham had the same experience, which he chronicled.

    Losing body fat without reducing carbs means that there were sufficient time periods in the day that insulin went to a baseline low enough between meals to permit release and burning of stored body fat. By keeping carbs above genuine low-carb, a meal would produce enough insulin even on the "reduced carb" diet thus storing fat absorbed from the fat in the meal. (In my experiment, the carbs were too low to trigger much insulin.) With the very low fat diet, the insulin triggered by the carbs would have little fat from the meal to store and so would not have the same fat-storing impact as a fat and carbs meal, as would be the case "in the wild." I think that is the key, the person has to be very low dietary fat for reduction of fat diet to work, to mitigate the effect of the insulin. So the design was result-oriented in that respect.

    The second claim is that low-fat outperformed low-carb. This was not established in general. Every low-carb advocate I have read has said there is a one to three week break-in period, perhaps longer, for the metabolism to shift to efficient fat metabolism. So this six-day study seems "designed" to measure results before the transition to predominantly fat metabolism has occurred. That part of the study appears to be chicanery. The projection is simply not empirical.

  23. Bjarte Bakke Team Diet Doctor
    You can lose weight on a low-fat diet. I think the main reason why is that the worst food sinners, processed junk foods and especially sugars, are not part of low-fat diets.

    Another interesting question to ask is:
    What way of eating will lead to weight-loss in both the short and long term and make the person feel great?

  24. Guido Vogel
    Table 4 shows insulin data:
    Insulin (pg/ml)
    Baseline 12.6 ± 2
    Reduced Carbs: −2.76 ± 0.77
    Reduced Fat: −2.04 ± 0.8

    So the low-fat group reduced insulin almost as much as the reduced-carbs group, with the same amount of carbs.

    It is possible to burn fat and reduce insulin without cutting carbs. That seems to be an interesting finding even though the low-fat diet is not a real-life diet.

    1) How does low-fat diet reduce insulin if carbs are constant in relation to baseline diet?
    2) Is reducing insulin still the only mechanism or are any other mechanisms at work? If yes which?

    If the researchers wanted to validate whether carb reduction was required to burn fat loss, why introduce a low-carb group. Why not all 19 on low-fat. That would have generated more robust data.

    Reply: #25
  25. murray
    I wasn't sure how to interpret the baseline insulin data on a quick scan of the report because the discussion section of the report said insulin did not decrease on the ultra-low fat diet.

    I still think the result is best explained by there being no dietary fat for the insulin to shuttle into fat cells post-meal and insulin levels would have abated by the time liponeogenesis had kicked in from the carb load. However, without the fat storing, the leptin signalling from fat cells would have been weak, which is why low-fat dieters typically report ravenous hunger in contrast to low-carb dieters. This might be sustained for six days in a metabolic ward with no subject-initiated food selection, but in real life success is influenced by eh effect of the diet on appetite. So the metabolic scenario is quite contrived.

  26. Guido Vogel
    @murray: thanks for the explanation. Bill Lagakos advised to skip all words in the article and just focus on METHODS and RESULTS :-)

    Lots of questions can and need to asked, but apparently reducing carbs is not the only way to reduce insulin/burn fat. Be it in a theoretical scenario.

  27. Melisa
    I'm glad I found these comments. I was shocked when I heard this "study" on the news stating that it was now a "fact" that low fat diets worked better. Really, after 6 days??
  28. Richard David Feinman
    What is reported for all the variables are averages and large variation. Do we really know what the results are. How many people did better on diet A and how many on diet B? Until we know that, we don't know what happened in the experiment.
  29. PhilT
    Re Problem 2 - the RC diet had an increase in fat oxidation that was quite a bit less than the reduction in energy intake, so they were drawing on carbohydrate (glycogen) reserves. This would have lasted about 8 days by my estimate.

    The RF diet took away ~800 kcal of fat and saw a small decline in fat oxidation, hence body fat was been drawn on to the tune of 700 kcal rather than the ~400 kcal in RC.

  30. Zepp
    Who bothers.. the studiy say that jojo banting works.. at least for six days.. who didnt kno that befor?

    They could have opened a book about human biocheia, instead!

    First there is a concern about a sustainable diet.. for free living humans!

    At second.. if they have opened that book they should have noticed that there are time for adaption for a ketogenic diet.. at least 3 weeks.. not six days!

    But anyhow.. they didnt try an ketogenic approche at all!

    I think those how got some knowledge, say that 20E% carbs is kind of a limit.. and less then that.. one enter in to a ketogenic state.. and then other things happen.. then a modest reduction of carbs!

  31. Martin
    This study baffled me for a day or two. How come 2.5 times more carbohydrate diet can result in more fat burned??? Then came up with two things:
    First- it was not a diet intervention only but has an exercise component (1 hour/day with intensity at will)
    Second- The 5 days baseline diet was always a very high carbohydrate diet.
    The two point relates in this way: When you eat a run-in very high carbohydrate diet you loose the machinery (enzymes and gene transcriptions ) to metabolize a reduced calorie, high carbohydrate diet (no high fat metabolizing machinery, if you ever have it prior to this). Then thrown to this hypocaloric diet and regime of one hour of exercise, you may find the exercise daunting. So you will choose the least exertion because you don't have the gas to do otherwise.
    Given a 5 days baseline diet of 25, 20, 55 carbohydrates, proteins and fats; and 55, 20, 25 carbohydrates, proteins and fats for the second row, would give slightly different results, I think.
    Furthermore, the exercise will reduce the glucose in blood and glycogen stores in liver and muscle, easing the job of insulin to drive glucose to be burned or stored in those tissues instead of the liver to turn those sugars to fat.
    The study design is acceptable, but the results could lead to wrong conclusions if you don't have background information...


  32. bill
    The researchers state in their discussion, "Furthermore,
    we can definitively reject the claim that carbohydrate
    restriction is required for body fat loss" referencing Taubes.
    They ignore that the claim was "..the only meaningful
    way to lose fat … is by reducing the amount of carbohydrates
    consumed." They disingenuously ignore the word "meaningful"
    and then design a protocol that could never accomplish any
    meaningful fat loss in humans. Heck, two of their subjects
    couldn't even stay on the diets through the whole study.
  33. Zepp
    Who cares.. for six days?

    Anything can happen in a six day trial.. thats the moste concern I have!

    Another thing is what happens in six months!

    The anohter thing to have concern about is if they ould achived the same thing free living?

    Well the study conferm that jojobanting works.. at least for six days.. anyone that have doubts about that?

    Its another waiste of money and time!

  34. Eric
    The study? Seems to have been designed for the results obtained. Who benefits from creating such stuff and passing it off as anything else but junk?

    Is this cover for the sponsors and sponsors of the sponsors?
    Follow the money!

  35. Wade Henderson
    Too funny, after years of everyone here touting the superiority of low-carb diets when put up against "low-fat" diets.... when the actual "low-fat" diets used were most often anywhere from 28% to 35% fat...
    Now everyone is screaming about the "low-fat" diet actually being a real "low-fat" diet, under 10%.. and the low-carb diet used for comparison, not being a real low-carb diet.

    Its like a mirror image of what has been going on here for years, using false "low-fat" diets and touting their poor results.
    Where was everyone here when false "low-fat" versions were used?

    People are funny, seeing and reading only what they want to see.
    Clearly a great portion of the population can lose weight on either "real" low-fat or "real" low-carb.
    As to 8% to 10% being impossible long term versions of low-fat, that is just silly.

    People can choose which diet fits their personal tastes and their particular health profile.
    Smart folks can carefully choose either one. Neither is superior for everyone.

    Reply: #36
  36. Zepp
    Who says that LCHF is superior for everyone?

    Who says that a fixed macronutrient composition is superior for everyone?

    Who say that macronutrient composition is the only thing one have to bother about?

    Who says that LCHF is the same for everyone?

    The thing is on this forum, that we provide advice for those that like to test a low carb diet/or a ketogenic diet!

    If one like to know what happens if one reduce carbs to 20E% or less.. there are plenty of information in books about human biochemistry!

    The thing is still that calorie counting is a tautology.. it dont explain that much.. about human biochemistry.

  37. Walker Casamayor
    When that gas is low, you need to refuel, which is where gels and GUs come in. If your body could burn fat, Phinney thought, you could go a heck of a lot longer before refueling. So Phinney put a small group of elite male cyclists on a low-carb diet to test it out—forcing their bodies to tap into the fat stores.
  38. Andreas, thanks for providing us with your clear take on the Hall paper. Yes, the RC group was burning more glycogen during the 6 days compared to the RF group and the model works. The paper does not provide anything practical in terms of treating obesity in the real world, Hall says that himself. Especially with hunger and appetite removed from the equation, the study was only a metabolic ward experiment looking at energy balance and NOT best diets.

    The big issues frustrating most are the misleading title (NOT head-to-head best diets) and the Taubes bashing. Guess Hall just wanted to get everyone's attention... mission accomplished.

    BTW, I heard Hall speak at ASBP in Denver this past April (we all missed your presence Andreas). He discussed his energy balance model. He's clever and I found it interesting.

  39. bill
    Here's another study by Hall, et al, which may
    be published in the near future:


    If you read this study protocol, you can predict
    Hall's interpretation:

    He has the same participants first eating a SAD
    where they will become or stay unhealthy. They
    will be out of shape after eating 300 grams of
    carbs and then 4 weeks of 50% carbs. Those
    same subjects will then start a 4 week transition
    to a ketogenic diet. So while these out of shape
    people will have the keto flu during their 4 week
    transition, that's when Hall will test their energy
    expenditure and disingenuously say, "See, the
    ketogenic diet is bad for people."

    Stick with Volek and Phinney for your information
    on performance and energy expenditure on a ketogenic diet.

  40. Ian
    The low carb trial had 8 times as much weight loss as the low fat, in the measly 6 days! 'The RC and RF diets both led to weight loss, but significantly more weight was lost following the RC diet.' (p7) Very 'significantly'. And yet their "mathematical model" showed little difference projecting well into the future?

    'Model simulations were used to design the study and the successful predictions of the observed 24-hr RQ changes were included in the clinical protocol.' (p9) ???

    Reply: #42
  41. Ian
    Did the model calculate for the highly nonlinear effect of carb depletion? They talk about net macronutrient oxidation rates, but does the model include the limited glycogen stores used up by the low carb process?
  42. Ian
    OK, it seems I was reading the model projection rather than the experimental data for weight loss (in Figure 3 F). There was still weight loss, and surprisingly different from the model. I still wonder what would happen when you hit glycogen depletion, which seems unlikely in a method allowing 140g/d of carbs for 6 days?
  43. Maki
    I think that the obvious problem with this study is that it had only 19 participants, with that few people individual differences between people will be more important for the results then diets used.
  44. Waleed Mahmoud
    I happen to think that contrary to all above comments, that although low fat diets are evidently the winner in shedding weight from people who are overweight; it is the low fat diet, or more accurately, the no fat diet that may proceed further in scraping off the remaining stubborn fat that is the main cause of major cardiovascular and metabolic illnesses.

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