Low-carbohydrate diet shown to have considerable potential to protect against type 2 diabetes

Type 2 diabetes is a condition characterised by generally elevated levels of blood sugar (glucose), usually as a result of ‘insulin resistance’ (insulin not doing its blood sugar-lowering job very well). Between a state of health and type 2 diabetes, the medical profession has defined a state known as ‘impaired glucose tolerance’ (IGT). Here, insulin functioning tends to be impaired and blood sugar levels on the high side, but not so bad as for the criteria of type 2 diabetes to be met.

In some respects, IGT can be thought of as a potential stepping stone between health and type 2 diabetes: 25 – 75 per cent of people with IGT go on to develop type 2 diabetes within a decade, apparently.

If someone was to give three words of advice for someone with IGT they would undoubtedly be ‘cut the carbs’. Cutting back on sugar and starch in the diet is what I have found works best for improving blood sugar control and perhaps retaining some insulin sensitivity. There are other things that might be considered too (such as physical activity, if this is not currently a feature of someone’s life), but scaling back carbohydrate intake would be my number one piece of advice.

I was therefore interested to read a recent study in which a ‘low carbohydrate diet’ (LCD) was trialled in a group of 72 individuals with IGT [1]. Half were educated about low-carbohydrate eating and encouraged to adopt this diet for a year. The other half of the group was left to its own devices. For a free pdf of this article, click here.

Here is a description of the intervention for the ‘LCD’ group.

The LCD group was admitted to hospital for 7 days to participate in an educational program. On the first day of the program, a physician gave a lecture about the LCD using slides that lasted for 60 minutes. On the second day, the subjects received individual lessons from nutritionists, pharmacologists, and nurses. After that, they ate the LCD every day and studied the diet using a textbook that was given to them. In compliance with the LCD, rice (the main dish) was offered at lunchtime only. The target was a total intake of 1,300 kcal per day. The nutritional composition of the food was 30% carbohydrates, 25% protein, and 45% fat. On the fifth day, the subjects completed some tests on the LCD (30 questions, true/false test), and discussed their diet with nutritionists, nurses, and physicians at a lunch meeting on the LCD. After that, they reviewed the diet and were discharged from hospital.

The individuals in this group were instructed to aim for a maximum daily intake of carbohydrate of 120 grams (a higher threshold than popular low-carbohydrate diets).

At the end of study, 12 months, the LCD group saw significant improvements in practically every parameter measured by the investigators, including:

  • Body weight
  • Fasting blood glucose level
  • HbA1c (measure of blood sugar control over approximately the last 3 months)
  • Fasting insulin level
  • Measures of insulin sensitivity
  • ‘Healthy’ HDL cholesterol level
  • Triglyceride levels

Crucially, about 70 per cent of the group saw a return on blood sugar levels to normal, compared to only about 8 per cent in the control group. Not one person in the LCD group developed diabetes during the study, compared to 5 (14 per cent) in the control group.

The results clearly show that compared to ‘doing nothing’, restricting carbohydrate helps people with IGT. One might argue that perhaps another sort of diet (e.g. a low fat one) would work even better. However, as the authors point out, other studies have found that in those with IGT, low-fat eating leads to a one-year incidence of type 2 diabetes of between 2.0 and 12.5 per cent. This does not compare so favourably the 1-year incidence of 0 per cent found in LCD eaters in this study.


1. Maekawa S, et al. Retrospective study on the efficacy of a low-carbohydrate diet for impaired glucose tolerance. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy 2014:7 195–201

31 Responses to Low-carbohydrate diet shown to have considerable potential to protect against type 2 diabetes

  1. Anna 4 July 2014 at 4:30 pm #

    I am always grateful to hear about these studies, despite being perplexed that good money and time are actually being spent investigating the obvious. I did not need a study to tell me that cutting carbs was the logical thing to do when I developed IGT three years ago. Like those in the study, I saw a return to normal blood sugar levels after adopting a low carb diet (30g net carbs per day) and I have not developed diabetes to date. It is nice to see this confirmed.

  2. Antje 4 July 2014 at 5:56 pm #

    In my opinion this diet was not only (relatively) low carb but also low calorie.
    Also the numbers confuse me a bit.
    30% of 1300 calories is 390 calories is 97,5 grams carbs.

    • Jonathan Bagley 9 July 2014 at 4:48 pm #

      Antje, the group given the LCD were told to aim for a maximum daily intake of 120 g a day during the long period of the study. They underwent a 7 day educational stay in hospital to help them stick to the diet long term. It was during this stay they were given the 30:45:25 diet which,as you say, works out at 97.5 g of carbohydrate.

      • Jonathan Bagley 9 July 2014 at 4:51 pm #

        Also the long term diet was unrestricted in total calories. Only the 7 day educational stay in hospital diet was restricted to 1300 cals.

  3. Suyaa 4 July 2014 at 6:24 pm #

    The results don,t surprise me at all. I finally put myself on a Vlcd because at my last diabetic review all the doctor wanted to do was give me was more medication. I said no way changed my diet completely and have lost one and a half stones in 2and half months! Prior to this I had never actually lost weight on any low fat diet ever. I look at all the rubbish out there think of my now brilliant blood glucose and svelte figure and know that I will never return to the proper diabetic diet that was actually making things worse ! We need more evidence like this it is clearly the only way to go and makes me wonder why more people aren’t obese!”

  4. Stephen Rhodes 4 July 2014 at 6:42 pm #

    There is now fairly conclusive evidence to indicate that the number of copies of the AMY1 gene an individual has is inversely associated with the likelihood that they will become obese, leading Professor Tim Spector, Head of the Department of Twin Research and Genetic Epidemiology at King’s College London and joint lead investigator to say:
    “These findings are very exciting. While studies to date have mainly found small effect genes that alter eating behaviour, we discovered how the digestive ‘tools’ in your metabolism vary between people – and the genes coding for these – can have a large influence on your weight. The next step is to find out more about the activity of this digestive enzyme, and whether this might prove a useful biomarker or target for the treatment of obesity.

    In the future, a simple blood or saliva test might be used to measure levels of key enzymes such as amylase in the body and therefore shape dietary advice for both overweight and underweight people. Treatments are a long way away but this is an important step in realising that all of us digest and metabolise food differently – and we can move away from ‘one-size fits all diets’ to more personalised approaches.”

    [Read more: Link Between Obesity and ‘Carb Breakdown’ Gene Identified | Medindia http://www.medindia.net/news/link-between-obesity-and-carb-breakdown-gene-identified-134039-1.htm#ixzz36Wem0DKr ]

    Elsewhere I have read that it those with higher numbers of copies of the AMY1 gene who have better blood sugar control, and that this is considered to be the mechanism by which obesity does not result in that cohort.

    Should these studies not also have looked for IGT to see if it is associated with the number of copies of the AMY1 gene as the AMY1 gene count should be a more definitive test than measuring salivary amylase?

  5. Vicente 4 July 2014 at 7:39 pm #

    Thank you Dr Briffa for this interesting post.

    A friend of mine is a T2D and has recently started a low-carb diet. His blood glucose levels have returned to non-diabetic levels except just after waking up (dawn phenomenom?). Now he is using less insulin than he used to. He is really excited with the results.

    His doctor doesn’t know about the new diet, so he is on his own.

    My point is that we need the health authorities to stop recommending T2D to eat the foods that make them sicker and sicker day by day. Health authorities have a lot of power of influence and I am afraid that when faced with the dilemma of a) eating what they see make them healthier or b) following their doctors’ recommendations, most diabetics would choose the latter. I suppose my friend would. And it is not his fault.

  6. Brenda 4 July 2014 at 9:23 pm #

    I had 2 parents with T2 diabetes (one on insulin) plus 2 siblings and cousins etc. I went on a very LC diet for preventative reasons and the proof was in my recent bloods tests for A1c down from normal 5.2 to a better 4.8. I plan to stick with this way of eating for good.

  7. William L. Wilson, M.D. 4 July 2014 at 10:48 pm #

    There’s no question that a low carb diet can prevent or reverse type II diabetes. The problem is, the medical profession doesn’t seem to be interesting in this approach. They want to “manage” diabetes using drugs and insulin. They want patients to “count” carbohydrates but to me this seems ridiculous. Can anyone say “dog chasing tail”? Physiicans get paid very well to do so but get nothing for preventing or reversing diabetes. According to this approach physicians should have donuts in their waiting room!

    Thankfully there are still a few physicians like Dr. Briffa and myself who do the right thing regardless of financial issues. The good news is that patients can grab the bull by the horns and take of the problem without any intervention by the medical profession. All you need to do is eliminate processed food and transition to a whole foods diet. It’s low risk and simple. What more could you ask for?

  8. Nigel Kinbrum 5 July 2014 at 5:23 am #

    “The nutritional composition of the food was 30% carbohydrates, 25% protein, and 45% fat.”
    The energy composition of the food was 19.2% carbohydrates, 16% protein, and 64.8% fat.

  9. Edward T. 5 July 2014 at 7:05 am #

    Great post and comments. I noticed 2 out of 6 commentators used VLCD diets with no mention of reduced carbs – I’d be very interested to hear Dr. Briffa response on this approach v. simply lowering carbs by eating real food

    • Dr John Briffa 5 July 2014 at 9:40 am #

      Hi Edward

      Different people have different tolerance of carbohydrate, and therefore different approaches are legitimate. I generally advise a diet lower in carbohydrate than is traditionally advised, but I’m also open to the idea of very low carbohydrate diets, particularly in individuals who appear to have very low tolerance of carbohydrate.

      • Stephen Rhodes 5 July 2014 at 12:35 pm #

        “particularly in individuals who appear to have very low tolerance of carbohydrate”

        The trick will be spotting those individuals before they have done themselves any serious damage.

        Do you know whether there is any initiative to carry out genetic testing for the number of copies of the AMY1 (and AMY2) genes an individual carries – ideally in childhood and possibly along with blood typing as it may prove to be that important over a lifetime?

        It must be possible since the research that has been carried out specifically determined this parameter.

      • M. Cawdery 5 July 2014 at 6:11 pm #

        Your comment “One might argue that perhaps another sort of diet (e.g. a low fat one) would work even better.” surprises me.

        Carbohydrates (complex, starch etc) are all absorbed as C6 sugars, mostly glucose (stimulating insulin) or fructose (converted to triglycerides in the liver). Why then should a low fat diet “work even better”?

        Glucogenesis from protein or fat would be limited presumably to specific need.

        • Dr John Briffa 6 July 2014 at 6:58 am #

          M. Cawdery

          Yes, I agree it’s nonsensical that a low-fat diet would be the best diet for those with IGT, but you know there are many health professionals who still advise this very diet (complete with ‘starchy carbs at every meal’) to those with type 2 diabetes or its precursor. As you know, I don’t favour this sort of diet at all.

        • Sean Raymond 18 July 2014 at 9:28 am #

          Hi M. Cawdrey.

          I just wanted to point out that fructose isn’t converted to fat via de-novo-lipogenesis in the way as is commonly believed and which you suggest. This myth seems to stem from animal studies where indeed it appears that in Mice about 50% of it will be converted to TAG. However, in humans the science seems pretty conclusive – under 5% of fructose will undergo DNL. However, even if it was converted to fat, you need to ask yourself a question – what would be the issue? I say this because when you eat fat (which doesn’t need to be converted to TAG!) this doesn’t automatically mean that you will increase adiposity so even if fructose was converted to fat at a rate of 50% (which it certainly isn’t) we can see that within the context of energy balance this isn’t going to matter.

          When I argued this point recently I was told that what I had said is too simplistic and that when fructose is consumed we would be in a fed state, meaning we will be awash with insulin meaning that lipogenesis is underway which will result in that fructose becoming storage lipid whilst fat itself does not cause insulin release. I am sure you are aware that we do not eat diets that are so compartmentalised and that the meals we eat are mixed and so we will always have an insulin response when food is consumed. Regardless, I personally do not hold to this idea that the insulin response itself causes adiposity as is argued by the like of Gary Taubes – although the idea is interesting I feel there are too many holes which haven’t been explained.


  10. Ellen K 5 July 2014 at 7:25 am #

    Speaking as a fattie, it’s quite inspiring to read that losing 10% of your body weight along with a modest reduction in carb intake can produce such a positive result. At least in the short term. And if you are Japanese.

    Still, worth a go.

  11. M. Cawdery 5 July 2014 at 9:50 am #

    I seem to remember that a study was done (Newcastle???) on a very low calorie diet (~600 Kcals/day Kcal is what is usually called “a calorie”). The result was a “cure” but I suspect that it was in new cases of Type 2.

    • Jonathan Bagley 9 July 2014 at 5:02 pm #

      A Ch 4 programme was made testing the Newcastle 800 cal diet against an unrestricted calorie low carbohydrate diet, which won hands down. The people on the 800 cal diet became miserable, couldn’t keep to it and the outcomes were worse. Nevertheless, the Newcastle researchers still keep banging on about the wonders of 800 cals a day and this event has almost been airbrushed from history, except for here


      Scroll down to Extreme Diet Ward, August 2013. From what I recall, this is an accurate account.

      • Jonathan Bagley 9 July 2014 at 5:02 pm #

        correction: not an unrestricted calorie diet, but 1600 cals a day.

    • David 9 July 2014 at 11:12 pm #

      There was a study but it’s gone quiet. Low carb, severely so, and monitored. “Cure” perhaps, but I don’t recall it being restricted to new cases. Anybody know?

  12. Vierotchka 6 July 2014 at 8:04 pm #

    Never fond of carbohydrates and sugar, I have been for decades on a low to no carbohydrates and no sugar way of eating. That did not prevent me from developing Type 2 Diabetes and becoming obese after my menopause.

    • Cindy C 7 July 2014 at 3:59 pm #

      I wish we could always prevent diabetes, but we are affected by how our parents and grandparents and on down ate, as well as gene mutations, hormones, antibiotic use, stress, chemicals in the environment, and so on. If you waited until menopause, you were likely doing things to delay it, thus preventing some damage.

      • Ellen K 9 July 2014 at 2:09 pm #

        Diagnosed Type 2 two years ago but it seems to have left me since I ….. er, stopped drinking. It took about a year but it slowly left me. If I were tested for the first time today, I would be “normal, no action” and I’m not taking any diabetes drugs but now I am stuck with this horrible diagnosis.

        But it is worth a go, all you T2s out there. Just think of all the money you’ll save. And you will still be able to eat cakes.

  13. Cindy C 9 July 2014 at 3:56 pm #

    This was in the news today. I have read similar. We do know what we eat affects our microbiome to some extent. Our mood, and health can improve by what we eat, but we are a long way from solving all our health problems with diet, and changing our microbiome alone.


  14. Mike 14 July 2014 at 1:24 pm #

    The word is slowly getting out there.

    I was diagnosed with T2 last November with a H1ac of 8.3. I adopted VLC, mostly paleo approach and 7 months later my a1c is 4.2 and I am closing in on 100 lbs weight loss.

    My success was so dramatic that I converted my doctor to low carb and she is now recommending it to her patients.

    And the T2D diagnosis has been removed from my medical record. 🙂

  15. SueG 14 July 2014 at 3:46 pm #

    “but you know there are many health professionals who still advise this very diet ”

    You are correct. I accompanied my friend to her GP for the results of her blood tests, she was told the GP wanted to see her. As prophesied by me, she was told that her cholesterol was elevated (to 5.7 – wow) and her GP told her she was also a bit overweight. She proceeded to print out a diet sheet from the internet for her. This turned out to be a low fat diet, printed from the NICE website and was a diet devised by a Doctor in 2006 which was peer reviewed by ……. his wife, also a GP!

    The diet was compromised of advice I thought went out years ago, only 3 egg yolks a week, skimmed milk, low fat spreads. I was outraged on her behalf. Fortunately over the years she has actually listened to me and the diet sheet went into the bin. I suggested she wrote to the practice to remonstrate with them but that’s a step to far for her so I have to be content with knowing that she will ignore the advice. Just how long is it going to take for whoever authorises such “wisdom” to update to proper, sane, diet recommendations? Who is actually in charge of dispensing guidelines for GPs?


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