How ketogenic (low carb high fat) diets work

A really nice paper was just published by Paoli, Rubini, Volek and Grimaldi in the European Journal of Clinical Nutrition titled “Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets”

You won’t see a better review paper for summarizing the latest in how we think carbohydrate restriction affects various aspects of metabolic health; from weight loss to neurological issues to acne (yes acne!).

A second excellent review article was also published in Nutrition Today by Volek (again!) and Phinney, the low carb gurus. This one is called “A New Look at Carbohydrate-Restricted Diets: Separating Fact From Fiction”. Again this is an excellent scientific review paper.

What I should be doing in this blog is simply drawing your attention to this good work and you can go and check it out for yourself.

Except I’m aware that unless you work at a university, that’s easier said than done. You’d have to buy the papers, which means that most of the people who stand to benefit from the knowledge won’t.

Actually, copyright publishing is a scam of the highest order. What happens is that guys like Volek and Phinney put in heaps of work, often that work is paid for by either public institutions, or by research grants gained through public funds. They then (usually) slave away in the degrading process of blinded peer review, often having to respond to inane comments and endless rebuttals. When they are done, they then sign all of their IP over to a journal, which keeps it all for no cost (and all profit) in perpetuity. Can you imagine anywhere else in the business world that would happen besides academia? It’s laughable, but it is actually what happens to us academics everyday and frankly, we no longer find it funny.

Anyway, I digress. What I really want to do here is summarize the two reviews.

Let’s start with the Nutrition Today paper by Volek and Phinney, which is a nice synthesis of the available evidence for the biology of human energy regulation and homeostasis, and how a carbohydrate restricted diet operates. The main points here are:

  1. Saturated fat levels in the blood are not associated with dietary saturated fat intake, but dietary carbohydrate intake. They show evidence from both randomized controlled trials and population data for this.
  2. They discuss in detail what the keto-adapted (fat adapted) state is; how this comes about, including increased beta oxidation of fat, decreased hyperinsulinemia, and a reorchestration of substrate utilization in the body, including the use of ketones to fuel brain function. It is interesting that the majority of practicing dietitians, endocrinologists, cardiologists, and public health physicians have never heard of any of this.
  3. They point out what is a very important and obvious set of outcomes, which are well documented in the scientific literature; that treating a patient with insulin resistance with a low fat/high carb diet is palliative and going to make the problem worse. If you are having trouble getting glucose into your cells, then reduce the glucose load stupid!
  4. They show a nice little diagram, which I have reinterpreted and redrawn below, to show the role of dietary carbohydrate in metabolic (dys)function. To quote the authors “The major point is that SFA (saturated fatty acids), and the response to eggs, has a totally different metabolic behavior when consumed in the context of a low carbohydrate diet.”Slide1
  5. They show a meal plan for a typical low carb daily meal. This is excellent as it shows what real and tasty foods we are talking about.

2500 kcal daily food intake restricting carbs

Breakfast (scrambled eggs with sides of spinach and sausage)

  • Scrambled eggs: 2 large + 1 tbsp palm oil
  • Mozzarella cheese: 1 oz
  • Pork sausage: 2 links (48 g)
  • Chopped frozen spinach, boiled: 3/4 cup (142.5 g) + 1.5 tbsp butter


  • 1/2 Avocado: 67 g
  • Swiss cheese: 2 oz (56 g)

Lunch (broiled salmon and a side salad)

  • Broiled Atlantic salmon: 4 oz + 1 tbsp butter
  • Mixed baby greens: 2.5 cups
  • Diced tomatoes: 1/4 cup
  • Chopped onion: 1/8 cup
  • Feta cheese: 1 oz
  • Black and green olives: 4 each
  • Blue cheese dressing: 1.5 tbsp


  • Peanuts, oil-roasted: 1 oz
  • Hood Calorie Countdown milk: 1/2 cup

Dinner (sirloin with sauteed mushrooms and cauliflower ‘‘mashed” potatoes)

  • Beef sirloin tips: 3 oz
  • Olive oil: 1.5 tbsp
  • Sauteed mushrooms: 1/4 cup
  • Olive oil cooking spray
  • Cauliflower ‘‘mashed potatoes’’: boiled cauliflower 1 cup + shredded cheddar cheese 1 oz + Butter 1 tbsp
  • Sugar-free jello: 1/2 cup (121 g)


  • Protein: 134 g
  • Carbohydrates: 42 g, Fiber 20 g
  • Fat: 204 g
  • Cholesterol: 853 mg
  • SFA: 81 g
  • MUFA: 78 g
  • PUFA: 28 g

Reproduced from Volek and Phinney (2013), Nutrition Today

Now on to the second paper in the European Journal of Clinical Nutrition titled “Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets”. This is a comprehensive scientific review of the evidence and emerging evidence for the treatment and prevention of a range of chronic diseases with carbohydrate restricted (ketogenic) diets. I have adapted one of their figures into two new ones, showing the state of scientific evidence (strong and emerging separately) for “therapeutic uses of the ketogenic diet”. Hopefully these figures are self-explanatory.

I draw your attention to the “suggested mechanisms” under each one. I’m not going to go into these in detail but it is worth looking at these two figures and noting a few things:

  1. Carbohydrate restricted diets are a legitimate and well documented approach to the treatment of a wide range of issues.
  2. There are common mechanisms, mostly about reducing the load of insulin the body has to deal with. This is because the body has to dispose of less dietary carbohydrate. This point is seemingly lost on most in the field of chronic disease prevention and treatment. Hyperinsulinemia is a problem in itself, reducing it helps.
  3. As well, there are associated mechanisms associated with high insulin. There are problems in the IGF pathway, mitochondrial function, and inflammation.



There is now strong evidence to show that low carbohydrate diets are safe and effective treatments for several conditions, and have some likely positive effects for other conditions.

So that’s it. Two great papers. Hopefully I have captured the essence of what they are saying and where the evidence is at. This is important to get out there into the public and health community. While it’s all behind the paywalls of journals it won’t. So hopefully this helps.

44 Comments on “How ketogenic (low carb high fat) diets work

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  2. Thank you for this excellent summary. Could you please make some comments on the appropriateness of a low carb, high fat diet for endurance athletes?

    Thank you in advance!

    Best regards,

    Kasper Janssen
    Sport physician
    The Netherlands

  3. Excellent post and linkage here Sir. You’ve nailed the academic writing/publishing process to the letter.

    • THat’s fair enough, we all have our opinions. I think you are correct about excess of everything. I agree that part of that is environmental. But, two points. First weight and energy homeostasis is largely hormonally drive and those hormones are insulin and leptin. Insulin is largely controlled by glucose intake.

      MOst important though is too look at experimental trial where different approaches are pitted against each ther. I linked one of these above – out last week where the LCHF approach outperformed the other(s). If you have data on a better performing regime then I’m prared to change my mind as any scientist should be….

  4. Thank you for the the review. What are your thoughts on the place of Low GI / high GI foods in this debate?

  5. Hi grant, ive just started following your blog and find the information insightful and refreshing . Ive been doing my own low carb thing and have really noticed an improvement in overall energy levels and mood. The big kicker is after recovering from a hamstring injury, i was worried about energy levels while exercising. Now im mot where i want to be(15 weeks away) but im easily getting through 3 hour runs(70-75% heart rate) on water. I cant wait to tackle an ironman and some ultras. Are you aware of the work prof Tim
    Noakes does and is he aware of your work? Also have you heard of Tim Olson? He just won the western states 100mile run for the second year in a row, he is a low carb athlete who
    Is just smashing it. Love the blog and i cant wait to read some more.
    Heres a piece on tim olson

    • Tht ankhs yes I know of both Tims and communicates bit with Tim Noakes, who I awesome.
      Tim Olsen going well with LCHF but a GU per hour racing which is something we are learning from. Good luck and thanks for the support

  6. Hi Prof. Grant,

    Thanks for a good article. I also wrote about these studies from the point of view of acne.

    I was wondering if you could answer a quick question. As you probably know, some cases of acne are very much driven by insulin/IGF-1 signalling and in such cases adjusting dietary macronutrient ratio can be very helpful.

    I’ve just seen conflicting data on what’s the best approach to take. For example, I saw a recent systematic review of dietary composition to treat PCOS ( That paper concluded that as long as one sticks to low GI carbs and good quality fats dietary composition doesn’t matter that much. I’ve also read several studies comparing MUFAs to low GI carbs for insulin resistance. I don’t have the papers in front of me now, but as far as my memory serves MUFAs might have slight edge but nothing significant.

    Any comments? I haven’t seen the paper on Nutrition Today you talked about.

    • That’s a great question. The answer I think depends on how insulin sensitive you are. I think I want to cal that “metabolic health”. If you can move glucose out of your bloodstream quickly then high quality carbs are great because they produce very small insulin and glucose peaks. On the other hand, and I think there are good data emerging on this, if you are insulin resistant then the glucose and insulin peaks will be high and the area under the insulin curve massive for even good quality carbs. This will drive up insulin and bugger up the IGF1 pathways leading to all sorts (including acne). I have written on this see

      Remember metabolic health is driven by diet, exercise, stress and the presence or absence of other toxins int he environment. Probably nutrition is the most important as that provides the actual glucose directly stimulating insulin.

      • Thanks for your reply. I also looked at your other post. Not too long ago a similar study was done in adule male with acne and showed 296% higher insulin level in OGTT as compared to men with clear skin.

        The problem, I think, with that post is that you mostly talk about short-term studies that indeed show higher insulin load for carb meals. I think this is not 100% in-line with longer studies that show improvements in metabolic health even in diets that are higher in carbohydrates.

        For example, this systemic review looked at different dietary approaches to T2D and concluded that the Mediterranean diet works the best. I don’t know that criteria for ‘low carb’, but it’s probably higher in carbs than what you would call low carb diet.

        Here’s another meta-analysis. Again the low-carb was still fairly high in carbs (<45%) and the results favored the lower carb diet.

        My point is that clearly even moderately high carb diets improve metabolic health, as long as those diets are 'healthy'.

        What I wanted to know is whether there's rationale for recommeding low carb or ketogenic diets over moderately carb restricted diets (say <40% of carbs) that are low in high GI carbs and otherwise healthy? Especially keeping in mind that sticking to a ketogenic diet is probably much harder than sticking to a moderately carb restricted diet.

      • I agree people do better on modest carb restriction especially compared with the standard American diet. The extent to which most people do better on a ketogenic diet to a lower carb one is debatable. My point though is if you are insulin resistant then you may have to consider more severe carb restriction. The thing is that a massive proportion of the population falls into this category.

        The major studies you quote a re all good but still have to be careful abotu what low carb means in these meta analyses. As you say <45 percent hardly qualifies.

        Also that producing more ketones might have other beneficial effects on cognition, sleep, inflammation in general etc etc which all need further work.

      • OK, perhaps best we can say at the moment is that there are no health harms in more severe carbohydrate restriction and that it may better for people with insulin resistance.

  7. Great site. Really useful account of workings of the diet. I’m a medical journalist in the UK and I’m getting very interested in this approach – wrote recently about synthesised ketones work at Oxford (can go into it more if that would be useful).

    I’m trying to reconcile accounts of the low carb diet that come from people using it to treat kids with epilepsy (about the only medically approved use as far as I can see and then used for a fraction of the kids it could benefit) and the account of sites like yours.

    The epilepsy dieticians describe it as pretty challenging – lots of butter,cream, very restrictive, few vegetables, constipation, need for nutritional supplements, something that is hard to do but worth it because having dozens of fits a day is far worse.

    But the tone of your accounts is much more relaxed, perfectly doable, in fact the best way to eat all the time.

    Seems to me one big difference is limit put on carb intake – the epilepsy lot say about 25 gm a day any more than that and you are likely to tip out of ketosis rapidly fill up glycogen stores and put on weight. Then have to go through 2 week run into get back into ketone production. Disaster.

    You don’t seem to have those worries.

    Who’s got a more realistic assessment?

    • Very good questions really. I am not sure I know the answer for epilepsy. I’ve gone for a “get fat adapted” and then use the dual fuel system of ketosis and glucose for the chronic diseases because I’m not sure you need to be in a state of nutritional ketosis all the time. In fact that might down regulate thyroid and leptin at least in some people leading to other issues.

      Epilepsy is a bit different (I’m not expert in that by the way) because it is acute. You are having seizures or you are not). Everything else we are talking about is essentially chronic disease through metabolic dysregulation.

      The dysregulaiton is because the system is running entirely on glucose and is hyperinsulinemic. Restoring normal human metabolic function is a matter of getting the carbs and insulin under control and people seem to do well.

      Epilepsy though is probably a related but different and specific mechanism. So who knows really if you can still get results by coming in and out of ketosis. If anyone else knows how strict you need to be on a case level I’d be keen to know.

  8. Click to access Long%20term%20effects%20of%20ketogenic%20diet%20in%20obese%20subjects%20with%20high%20cholesterol%20level.pdf

    All 66 subjects received a ketogenic diet consisting of less than 20 g of carbohydrates in the form of green vegetables and salad and 80–100 g of proteins in the form of meat, fish, fowl, eggs, shellfish and cheese. Polyunsaturated and mo- nounsaturated fats (5 tablespoons olive oil) were included in the diet. Gradually, the amount of carbohydrate is raised from the original 20 to 40 g in order to supply sufficient glucose to sustain the cells with few or no mitochondria such as erythrocytes, cornea, lens, renal medulla and leukocytes.


    To determine the effects of a 24-week ketogenic diet (consisting of 30 g carbohydrate, 1 g/kg body weight protein, 20% saturated fat, and 80% polyunsaturated and monounsaturated fat) in obese patients.


    The weight and body mass index of the patients decreased significantly (P<0.0001). The level of total cholesterol decreased from week 1 to week 24. HDL cholesterol levels significantly increased, whereas LDL cholesterol levels significantly decreased after treatment. The level of triglycerides decreased significantly following 24 weeks of treatment. The level of blood glucose significantly decreased. The changes in the level of urea and creatinine were not statistically significant.

    All 83 subjects received the ketogenic diet consisting of 20 g to 30 g of carbohydrate in the form of green vegetables and salad, and 80 g to 100 g of protein in the form of meat, fish, fowl, eggs, shellfish and cheese. Polyunsaturated and monounsaturated fats were also included in the diet. Twelve weeks later, an additional 20 g of carbohydrate were added to the meal of the patients to total 40 g to 50 g of carbohydrate. Micronutrients (vitamins and minerals) were given to each subject in the form of one capsule per day.

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  10. I know fat is the preferred energy for endurance activities, but what’s your take on people who perform hiit, maximum strength resistance training, or other anaerobic styles of training?

      • True, but with carbohydrates below 20-50 on a daily basis, how do the glycogen storage a used up get replenished if one is training 4-5x a week at these intensities?

  11. Hi Grant

    Thanks for this post, it’s so interesting ! My partner Clint and I are only ketosis newbies and trying to learn more about it for our own health. He’s a personal trainer (primal, not typical. More into MovNat-type training) while I used to be one so we’re both very much interested in health. We’re fans of paleo/primal eating as well.

    I have thyroid and parasite issues (among other things) so am trying to find the right nutrition for me in order to improve my health, and not have to take supplements unless absolutely necessary.

    ** Can you please provide any information on ketosis and it’s effect on hormones and also parasites/gut health, or any websites/resources to look at?

    So far we’ve only tried ketosis for 5-6 day periods then having a couple of days of normal paleo/primal eating. The first week I ever did it I was a cranky tired mess! Clint usually eats low carb anyway because he enjoys it so he was fine. But me with the hormone and other issues… I struggled! But now when we do it I’m fine. We don’t measure but we estimate we eat about 20-30g carbs per day when we’re trying to get into ketosis and we use the ketostix to test. I’ve been told the one-week-on-a-couple-days-off method is actually pretty good…

    ** what are your thoughts on that?

    I’d like to gather some more information and in a couple of months I’m hoping to see a local Weston A. Price-trained GP where I live (who often recommended ketogenic diet to patients) to see if his methods could assist me. My goal is to have balanced hormones, good energy levels, no acne, and a healthy weight before I try to have kids in the next few years. I’d also like to have a healthy happy gut too.

    Thanks for your help 🙂

    • I would say that if you are going to try ketosis then you probably need to be pretty strict for a few weeks on the carbs < then can go back to some carb cycling – one day a week extra carbs. In fact, if you have thyroid problems this will probably be essential to avoid down regulaiton of leptin and thyroid hormones.

      Regarding gut parasites, I'll read Chris Kresser's new book – he has the best advice there on this.


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  13. My husband suggested we try this after hearing you on Newstalk ZB recently. He had been feeling unwell for about 6 months and no doctor could find out what was wrong. The nearest thing to match his symptoms was diverticulitis, but even eating with that in mind didn’t seem to help. Until we started LCHF. We are both feeling marvellous with no low energy times and our skin is looking great, eyes clearer and hair shinier, but the big thing we are both really happy about is that ALL our aches and pains have gone! I had arthritic fingers and could not click my fingers, but know I can click away and there is absolutely no pain. I had also developed a very sore hip and knee which was keeping me awake at night and that is completely cured too. My husband feels the same – he is a farmer and ex rugby player and his sore elbow, shoulder and various other body parts are now completely pain free!
    However, one disappointing aspect is that we have only really lost 1-2kg each in the 6 weeks we have been doing this. We both experienced a bit of hunger at first, but now we know what to eat to keep us full and we are certainly not over the top. In fact I did wonder if we were eating enough fat, but maybe we are eating too much. So what should we cut down on? Fat or protein? We do eat a couple of pieces of fruit a day and a handful of almonds. I have also been making the scandinavian crackers from sunflower seeds/sesame seeds/flax seeds/chia/psyllium and we often have those as a snack with a bit of cheese or home made chicken liver pate. But not too much I’m sure. And we don’t eat large meals now. I could do with losing about 10kg and my husband could lose 5kg. We would love to stick with this as it suits us and we feel and look so much better. Any suggestions?

    • Look = I’d love to write something here about you guys – but would really need some diet data form you – the amount of carbs, protein and fat you are eating in grams each day – you would need ot record your diet for a few days on an diet calculator – like easy diet diary if you have an ipad or iphone or myfitnesspal online. Otherwise, its just too hard to make a guess abotu whats going on with you guys. I’d love to help if you can do this – regards Grant

  14. Hi Prof Grant,
    I love reading your posts, however, I had a question about LC/HF for hypothyroidism? From my personal experience of following a LC/HF diet of 1,800- 2,000 calories a day I have noticed a reduction in my thyroid hormones which increased my T4 and reduced T3 (even though I was on zinc and selenium supplements & iodine intake balanced). I also had a massive hypoglycemic episode (even though healthy weight & HBA1C normal). From analysis of my diet (on Foodworks) it looks like some days my carb intake was around 20g, other days around 50g. So my question is how can you determine the best level of carbs for healthy hormones? Have you read any good research on ketogenic diets for Hashimoto’s/Hypothyroidism or even Hyperthyroidism??

  15. Hi Prof Grant
    I have a few health issues (Diabetes 2, PCOS, Hypothyroidism, onset Diabetic Kidney Disease and Hypertension). I have done extensive reading on LCHF and have been adapted my lifestyle over the last 6 weeks. I’m doing well on LCHF, but I am worried about my kidneys. I have not found any literature on how this will affect my kidneys. Do you know of any research on the matter? Do you know any GPs that support this way of life in Auckland?

  16. Hi Prof Grant

    I have a few,health issues (Diabetes 2, PCOS, Hypothyroidism, Hypertension, onset Diabetic Kidney Disease). The traditional way of eating as per the food Pyramid was not working for me, I was gaining weight while starving myself. I had to take drastic action. I read about LCHF extensively and have adapted my lifestyle over the last 6 weeks. I have lost almost 7kg, reduced my insulins by 80% and feel great! My only concern is the effect this will have on my kidneys. I have not found any literature on the effect of LCHF on kidneys. Do you know of any research? Do you know of any GP’s that support this way of life in Auckland?

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  18. The weight and body mass index of the patients decreased significantly (P<0.0001). The level of total cholesterol decreased from week 1 to week 24. HDL cholesterol levels significantly increased, whereas LDL cholesterol levels significantly decreased after treatment. The level of triglycerides decreased significantly following 24 weeks of treatment. The level of blood glucose significantly decreased. The changes in the level of urea and creatinine were not statistically significant.

    All 83 subjects received the ketogenic diet consisting of 20 g to 30 g of carbohydrate in the form of green vegetables and salad, and 80 g to 100 g of protein in the form of meat, fish, fowl, eggs, shellfish and cheese. Polyunsaturated and monounsaturated fats were also included in the diet. Twelve weeks later, an additional 20 g of carbohydrate were added to the meal of the patients to total 40 g to 50 g of carbohydrate. Micronutrients (vitamins and minerals) were given to each subject in the form of one capsule per day.

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  21. I love your article, thanks for explaining! I find a low carb higher fat diet makes me feel more energetic and is perfect for fat lose and muscle retention!

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  24. I notice the above article mentions neurological disease but I hear little mention of the ability of a low carb diet being able to treat migraines – which I have found to be very successful. I was getting ‘stomach’ migraines with frequent aura which left me feeling out of sorts. I was highly sensitive to noise and people and had a lot of down time each day recovering, although I hid it well. Often I felt I had been run over by a truck – just by being around people. I didn’t realise how low level my functioning was until all my symptoms disappeared from eating low carb. I wish my doctor had suggested taking a look at my diet instead of handing out the pills.

    • No. Children need to grow and will have higher growth hormone levels, which may increase lipids in ketosis just because they’re using fat to grow.
      Or it may be due to undereating on the keto diet – for all we know, these children, many of whom have been seriously ill from birth, have trouble eating normally – as lipids are also raised in anorexia. These changes aren’t seen at all in epileptic kids on the modified Atkins or low GI diets, which are around 70g/CHO per day, so are specific to keto diets, are not always seen in these studies, tend to decrease with time, and have not been linked to any adverse outcomes.

  25. Pingback: Ketogenic Diet General Articles & Specific Disorders

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