Can a low carb diet cure diabetes?

A study was recently published in BMJ Nutrition, Prevention, and Health that looked at the effect of a low carb diet on people with type 2 diabetes, and specifically, whether the low carb diet could be used to reverse type 2 diabetes and normalize blood sugar levels.

Type 2 diabetes is the type that is caused by life style choices (as opposed to type 1, which is an autoimmune disease, caused by the immune system attacking the cells that produce insulin). The prevalence of type 2 diabetes has increased enormously over the last few decades, ever since governments started telling people to eat less fat and more carbohydrates.

Of course, correlation is not causation, but it seems reasonable to hypothesize that the increasing levels of type 2 diabetes seen at a population level are due to an increased consumption of carbohydrates. If that is the case, then it should be possible to cure people with type 2 diabetes, or at least lessen the severity of the disease, by getting them to decrease their carbohydrate intake.

That is the basis for this study, which was a cohort study that followed patients with type 2 diabetes at one General Practice clinic in the UK. The authors became motivated to do the study after noticing an 800% increase in the prevalence of diabetes among their patients over the course of 30 years, and after finding that standard dietary recommendations were completely ineffective at reversing diabetes.

A cohort study means that a group of people are recruited, and then followed over time to see what happens to them. There is no control group, and no randomization to different treatments. This makes it harder to say what effect an intervention has, something we will discuss more later in the article.

The study enrolled 128 patients with type 2 diabetes (27% of the total number of type 2 diabetics in the clinic) in a low carb diet treatment program, and followed them for an average of 23 months. The average age of the participants was 63 at inclusion in the study. The average weight was 100 kg and the average HbA1c was 66.

At this point we should probably do a little detour to discuss what HbA1c is. Glucose that’s floating around in our bloodstreams has a certain tendency to attach to our red blood cells. HbA1c is a measure of how much glucose the red blood cells have bound to them, which is a good proxy for the average level of glucose in the blood stream over the course of the last few months. A normal HbA1c is less than 42 mmol/mol. The limit where someone is diagnosed with diabetes is 48 mmol/mol. Between 42 and 48 is considered pre-diabetic, i.e. the person is showing signs of insulin resistance, but has not yet developed full blown diabetes.

The low carb diet program in the study involved a couple of ten minute one-to-one sessions with a doctor or nurse per year, in which patients were coached on a low carb diet. The number of such sessions varied depending on the needs of the individual, but averaged three sessions per participant per year. The participants were also given low carb guidance during their other appointments with doctors and nurses. Optional 90 minute group sessions were also offered every six weeks.

Participants were recommended to avoid cereals, pasta, rice, bread, cakes, biscuits, and tropical fruits (bananas, oranges, grapes, mangoes, pineapples). Instead they were recommended to eat meat, fatty fish, full fat dairy, eggs, nuts, vegetables, and berries (blueberries, raspberries, strawberries). Certain fruits were also considered ok, such as apples and pears.

So, what were the results?

Over the course of follow-up (average 23 months), participants mean HbA1c decreased from 65 to 48. That is a huge reduction, and it is highly statistically significant. It means that the average participant on a low carb diet was able to go from having full-blown type 2 diabetes to a state of being pre-diabetic.

All other health markers studied also improved to a significant extent. Average weight decreased from 100 kg to 91 kg. Average systolic blood pressure decreased from 144 to 133 while diastolic blood pressure decreased from 83 to 78. Those number might not mean much to many readers, but a reduction from 144 to 133 means going from being diagnosed with hypertension to having a blood pressure within the normal range. So not only did the average patient stop fulfilling the diagnostic criteria for type 2 diabetes, they also stopped fulfilling the criteria for hypertension.

One criticism of a low carb diet from proponents of standard dietary recommendations is that it increases cardiovascular disease. This is based on the cholesterol hypothesis (which we’ve already debunked earlier on this blog), i.e. the belief that if you eat more saturated fats then your cholesterol levels will go up and you will get more cardiovascular disease. If you eat less carbohydrates, you will generally compensate by eating more fat, which is why those who believe in the standard recommendations are usually against a low carb diet.

That is why the doctors who performed this study measured the cholesterol levels of the participants. What did they find?

Total cholesterol decreased from 4,9 to 4,4 mmol/l, while HDL (so-called “good cholesterol”) increased from 1,2 to 1,3 mmol/l. At the same time triglycerides (fats in the blood stream) decreased from 2,6 to 1,7. Basically, all markers for cardiovascular disease moved in the right direction, not the wrong direction. So, it seems that the fears of proponents of standard dietary advice are unfounded.

It didn’t matter whether participants had had type 2 diabetes for a long time or a short time, or whether they had full blown diabetes or were just pre-diabetic, or whether they were older or younger. Everyone benefited from the low carb diet, and the biggest benefit was seen in those participants with the highest HbA1c at the start of the intervention.

Among the participants in the study, 29 diabetes medications were stopped, while four were started. 54 participants were on diabetes medications at the start of the study, and of these, 19 were able to become completely medication free. So overall, there was a big reduction in use of diabetes medications among participants. And apart from the reduction in diabetes medications, there was also a 20% reduction in the use of blood pressure medications.

Among the participants who had type 2 diabetes at the start of the intervention, 46% were in drug free remission at the end of the intervention (in other words, they had been cured of their type 2 diabetes, since they no longer fulfilled the criteria for it). In a normal GP practice offering standard dietary advice and regular treatment routines, only 2% are in drug free remission after two years.

What can we conclude?

First of all, there are weaknesses with this study. The biggest weakness is that there was no control group. Without that, we can’t say what would have happened to a group that was getting some kind of sham placebo treatment, and we can’t say how big the benefit of low carb is when compared with that.

On the other hand, most doctors who treat people with type 2 diabetes would probably agree that it’s relatively rare to see people go in to disease remission. As stated, only 2% are in drug free remission after two years with standard recommendations. And, in general, in a group of patients with type 2 diabetes, the number of medication prescriptions increases over time, it doesn’t decrease. That does suggest that the low carb intervention is effective.

A second problem with the study is that there was significant risk of selection bias. Participants who choose to take part in a study are usually more motivated than the average patient, so the benefit seen is often greater than would be seen in the real world. That being said, the results from this study are so impressive that, even if the real world results are much smaller, that could still mean huge health gains for a lot of people.

This study should be followed up by a large randomized controlled trial, in which participants with type 2 diabetes are randomized to either a low carb diet or standard dietary recommendations and followed for a few years, in order to confirm the results and get a clearer idea of what benefits can be expected. Although such trials have been performed earlier, they have invariably been small and/or short term. In the meantime however, I do think it makes sense for people with type 2 diabetes to try the low carb diet that was used in this study, after consultation with their primary care provider, of course, and see what happens.

You might also be interested in my article comparing a low carb vs a low fat diet for weight loss or my article about why deprescribing medications is so important for health in the elderly.

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25 thoughts on “Can a low carb diet cure diabetes?”

  1. Great review that also ties into lifestyle recommendations for the prevention of severe Covid 😉
    There are also studies that looked at the potential of a ketogenic diet (as a more extreme variation, the “no-carb diet”) for diabetic patients, among other indications. https://pubmed.ncbi.nlm.nih.gov/31185843/ , and there have been some complete reversals seen.
    I met some diabetics that had been on that diet for several months, and they reported the surge of energy and vitality they felt with it. Fascinating stuff!

  2. This may be of interest: https://www.theguardian.com/society/2016/apr/07/the-sugar-conspiracy-robert-lustig-john-yudkin A diet I really like, that is high in protein, complex carb and low in animal fat, is this one https://www.valterlongo.com/daily-longevity-diet-for-adults/

    I must say, the above story, plus the unsubstantiated assertions about cholesterol and heart disease, plus the insane reaction to the pandemic have destroyed my trust in the medical profession. While I have been fortunate to come across a few great doctors who looked after my family and I the majority have been fairly mediocre and some have come up with disastrous recommendations. I live in the US where the health care system is the most insane of developed countries and maximizing my longevity to me means relying on a healthy lifestyle and minimizing my interactions with the medical profession.

  3. Dr. Rushworth, it is a pleasure to read this analysis, and may I add something instead of trying to pick errors..

    You may want to have a look at Virta Health (U.S.) and DiRECT (GB) studies on this topic. Ketogenic and brutal caloric deficit (800kcal) approaches were both succesful as above. BTW, DiRECT had 50% of carbs but that was only 130g/d -I guess unintentional low-carb. The “control” group was usual care in both. Which were proven “useless care”, as you more politely mention above. When do they ever learn…when 1% absolute improvement in statin trials was fanfared, it is easy to ignore 67% improvement in T2D diets? Both trials run for more than 2 years. “Control” in quotation means that everybody knew their group. Virta was voluntary, DiRECT was treatment center -based “randomisation”.

    “cured of their type 2 diabetes…” Strong word, but DiRECT published resently a subgroup analysis, where people actually could rebuild the volume of pancreas. This is “cure in earnest” and may enable a full diet later -big news really. If you only cope with restricted diet (low carbs), you are managing a remission.

    The paradox in this context is, that you can not blame the carbs / sugar only for developing T2D. However, if you want to come back, less-carbs mean two edged sword; directly less glucose, but more importantly, less insulin aroused by it. After all, your energy balance as well as hormonal balance is amok when T2D. Now, the 1M$ question is, would this approach help while developing T2D (a process for 10-20 years before blood glucose, the last red flag, alarms)?
    JR

    1. Hi JR,
      Thanks for your comments. Do you mean if a low carb diet can help avoid developing type 2 diabetes in the first place? If that is what you mean, it seems so, since in this study people who were pre-diabetic reverted to having a completely normal HbA1c.

  4. You don’t have any discussion of the patients’ weight. Most people with Type II diabetes are overweight and that seems to be confirmed by your stated average weight of 100 kg.

    My wife is diabetic and weighs 40 kg. (she’s not underweight) It is very important not to generalise about what’s good for diabetics without stating which sub-population of diabetics the advice might be sensible for. There are other causes.

    1. Hi David,
      Is your wife type 1 or type 2? This article is about people with type 2. It is rare for a person with type 2 to not be overweight. But being overweight was not a criterion for inclusion in this study, so there’s no reason to assume that the same benefits couldn’t be accrued even by people with type 2 who have normal weight.

  5. Great article. It was very interesting to learn about how diabetes is actually measured, and how the numbers can be brought down. I had heard that the Ketogenic lifestyle helped with diabetes, as it is low-carb, and now I can see why!

    I’m curious, what are your thoughts on the plant-based/vegan lifestyle in terms of health?

    1. Hi Megan,
      I intend to write articles on this in the future. My personal take is that humans are biologically designed to be omnivores. Studies of paleolithic hunter gatherers have generally found that they got about 50% of their calories from meat, which is far more meat than we eat in western society. I’ve seen a number of vegans in the emergency room with anemia due to severe iron or B12 deficiency. It’s certainly possible to be healthy with a vegan diet, but I don’t think that’s the type of diet humans are evolutionarily designed to have, and therefore I think it’s harder and requires more effort.

  6. Dear Dr Rushworth
    I have recently been learning about the potential role of vitamin K2 in helping to remove calcium deposits from arteries and relocating those deposits to bone and teeth.
    Do you have any views regarding the use of vitamin K2?

    Vitamin K2 Goes Beyond Bone Health

    1. Generally, the way this is accomplished is by not telling the participants specifically which dietary intervention the intervention group will be getting, the participants just know that they are part of a diet study. Then you do low carb in the intervention group, and more traditional diet advice in the placebo group, and you see what happens. That way the participants are blinded to whether they are getting the active intervention or whether they are in the control group.

  7. While carbohydrate restriction has been shown to be therapeutic in many cases of type 2 diabetes, dialing back on linoleic acid and arachidonic acid intakes should, over time, improve insulin sensitivity in most people without having to resort to carbohydrate restriction. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5093368/

    A Mediterranean style dietary approach has been shown to improve markers of metabolic health. In a 2011 paper Norwegian animal science researchers wrote, “Combining reduction of the intake of arachidonic (AA) with enhancement of the intake of oleic acid will, moreover, also be a better strategy for reducing the total extent of in vivo lipid peroxidation, rather than adding more EPA (with 5 double bonds) and DHA (with 6 double bonds) to a diet already over-abundant in arachidonic acid and linoleic acid. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2875212/

    As for type 2 diabetes, the two big issues are insulin resistance and inflammation. For an excellent discussion regarding insulin resistance, search for Omega-6 Apocalypse on YouTube. To learn more about inflammation, Google – Endocannabinoid system saturated fat.

  8. Thank you for your article. I can confirm the results from my own experience. My type 2 diabetes was diagnosed in 2014 and I then took metformin. I was also obese and had high blood pressure and bad cholesterol. In January 2019 I switched my diet to low carb. Three months later I went for a blood test and my doctor couldn’t believe it. During the interview he congratulated me five times on my blood values, which were all within the normal range. After 6 months, I stopped both the metformin and the high blood pressure medication. After a year I had lost 43 kg.

  9. I enjoy each and every post on your excellent blog. Thank you very much for your exceptional work. When it comes to nutrition and diseases caused by wrong nutrition it seems to be pretty simple: Don’t eat crap, and don’t eat too much. No matter if it’s high quality super organic stuff or junk food, don’t eat too much of it. For me, the most important detail in the study is: Most participants were obese, and they lost weight. A carb-free diet might help. It is much easier to eat too much pasta than too much strawberries. A nice big bowl of super tasty pasta is usually way too much. We simply don’t need that much energy anymore. Let alone junk food with tons of hidden calories in it. Eat 100 grams chocolate, and you have to run around 60 minutes or 10-12 km to burn these calories. That’s a high price to pay for a bar of chocolate.

    1. Thank you for the kind words. Another aspect is that foods high in fat/protein/fiber are taken up from the intestine more slowly than foods high in carbohydrates, which gives a longer lasting sense of fullness, and thereby decreases the probability of over-eating.

  10. Thank you for a great summary of the study! I wonder if the results from the low-carb diet are simply the result of consuming a lower amount of calories overall. I don’t know if you’re familiar with Stephen Guyenet’s book ‘The Hungry Brain’, but the main idea is that our modern diet is filled with foods (even those made at home in the kitchen) that a great combinations of salt, sugar and fat. These foods hack the brain and other control systems that otherwise would normally prevent us from eating more than we need. Assuming a (hand-wavy) ‘one can only at so much meat (and other sating foods such as fat), is it simply be that the participants in the low carb diet benefitted from not eating as much as they otherwise would?

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