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Is Keto Appropriate for the Treatment of Diabetes?

Recent media articles have highlighted the debate between low-carb and low-fat diets for treating diabetes. In this article, Cliff examines recent media reporting and the evidence for diet and the treatment of diabetes.

The big fat debate over whether keto-style diets are right for reversing type 2 diabetes

John McCrone

Stuff News | August 19, 2019

Article Summary

“If a low carbohydrate diet could reverse type 2 diabetes, you would think experts would be rushing to recommend it. So why the caution?”

In this article, the case of Taupō GP Dr Glen Davies is highlighted. Dr Davies has been applying a low-carb dietary approach to treat type 2 diabetes for several years. The approach has led to the remission of diabetes and metabolic syndrome for many of his patients. However, the medical community and many in the research community are yet to embrace low-carb nutrition as a component of the treatment of metabolic disorder and diabetes.

Since the 1970s we have eaten more overall and we eat more ultra-refined and processed foods and this has led to an increase in the prevalence of diabetes, metabolic syndrome (pre-diabetes) and obesity.

Researchers like Otago University’s Professor Jim Mann have consistently criticised ketogenic diets due to the perceived dangers of saturated fat typically found in higher quantities in lower-carb and consequently higher-fat diets. He suggests that people should derive half of their calories from carbohydrate. On the other hand, Professor Grant Schofield of AUT takes a contrary position. He highlights that almost all the current research shows little to no danger from saturated fat.


In my humble opinion… (but what would I know, I’m only one of a handful of people who have actually completed their doctorates specifically in ketogenic diets!) low-carb approaches are the single best intervention for those with diabetes. To ignore this is to blatantly disregard the evidence for low-carb in relation to metabolic syndrome overall.   

What’s best for treating diabetes?

While many diets including the Mediterranean diet,1-4  and vegan and vegetarian diets5 can improve blood sugar control and help to reduce the risk of developing diabetes (in fact, ANY diet that is based on natural, unrefined foods is likely to help you avoid diabetes), the research is also clear that low-carb diets are the most effective for treating diabetes.

the research is clear that low-carb diets are the most effective for treating diabetes

Low-carbohydrate diets significantly reduce blood glucose levels and improve glucose control.6 They also consistently improve the most important cardiometabolic risk factors such as triglycerides and HDL cholesterol, more than standard-care, or higher-carbohydrate diets,7 which stands in contrast to the claims of cardiovascular risk from these diets (and remember that those with insulin resistance adhere better to carbohydrate restricted diets).8 Overall, low-carbohydrate and ketogenic diets are more effective than other dietary interventions for the treatment and management of diabetes with an approximately 150% greater reduction in HbA1c (a measure of average blood glucose levels) as a result of low-carb diets.9

…but should we be worried about saturated fat in low-carb diets?

There is an almost complete lack of any strong evidence that saturated fat worsens cardiovascular (heart and vascular) health. I have reviewed aspects of this evidence in previous articles and issues of CARR and almost all reviews of the scientific evidence find little or no association between saturated fat intake and CVD mortality.10-12  For example, a Cochrane review of randomised studies of the effect of modified or reduced-fat interventions on total and cardiovascular disease (CVD) mortality by Hooper and colleagues showed no overall effect of the diets on either outcome (total mortality: relative risk 0.98, 95% CI: 0.93 to 1.04; and for CVD mortality: relative risk: 0.94, 95% CI 0.85 to 1.04).13 That notwithstanding, some few people might experience significant worsening of LDL cholesterol when on a low-carb diet that is significantly high in saturated fat. I have found in clinical practice (assuming a low-carb diet is actually indicated for the client) that a simple substitution of some higher saturated fat oils (like butter and coconut oil) for unsaturated oils like olive, flax, and hemp, addresses this rapidly.

What about fibre?

In the article above, Professor Mann makes the point that high ‘high carb’ diet is mostly necessary to address getting enough fibre. However, one does not need to be higher carb in order to get enough fibre and gut-supporting resistant starches. In fact, in my experience, often when people are attempting to follow standard dietary guidelines, they end up eating relatively low amounts of fibre, especially in relation to their overall carbohydrate intake, because they are eating a lot of low-fat, high-carb, refined foods that are listed as ‘heart-healthy’ options (i.e. ‘heart tick’ foods). A lower-carb diet that includes plenty of veggies contain plenty of fibre and this has been demonstrated in research led by my colleague Dr Caryn Zinn, in which their healthy, low-carbohydrate diet exceeded recommended fibre intakes by 50%.14

Research by Dr Caryn Zinn has shown that a healthy, low-carbohydrate diet exceeded recommended fibre intakes by 50%

The take-home messages from the evidence are that:

  • Low-carb diets are most effective for the treatment of diabetes
  • Those with existing metabolic syndrome are likely to adhere to low-carb better
  • Saturated fat intake is not of major concern in a low-carb diet
  • Low-carb diets based on healthy, unrefined foods contain more than the recommended intake of fibre
  • Diabetes risk can be lessened through any diet that is based on natural and unprocessed foods


1.            Esposito K, Maiorino MI, Ceriello A, Giugliano D. Prevention and control of type 2 diabetes by Mediterranean diet: A systematic review. Diabetes Research and Clinical Practice. 2010;89(2):97-102.

2.            Schwingshackl L, Missbach B, König J, Hoffmann G. Adherence to a Mediterranean diet and risk of diabetes: a systematic review and meta-analysis. Public Health Nutrition. 2015;18(7):1292-9.

3.            Esposito K, Maiorino MI, Bellastella G, Chiodini P, Panagiotakos D, Giugliano D. A journey into a Mediterranean diet and type 2 diabetes: a systematic review with meta-analyses. BMJ open. 2015;5(8).

4.            Sleiman D, Al-Badri MR, Azar ST. Effect of Mediterranean Diet in Diabetes Control and Cardiovascular Risk Modification: A Systematic Review. Frontiers in Public Health. 2015;3(69).

5.            Lee Y, Park K. Adherence to a Vegetarian Diet and Diabetes Risk: A Systematic Review and Meta-Analysis of Observational Studies. Nutrients. 2017;9(6):603.

6.            Meng Y, Bai H, Wang S, Li Z, Wang Q, Chen L. Efficacy of low carbohydrate diet for type 2 diabetes mellitus management: A systematic review and meta-analysis of randomized controlled trials. Diabetes Research and Clinical Practice. 2017;131:124-31.

7.            Gardner CD, Trepanowski JF, Del Gobbo LC, Hauser ME, Rigdon J, Ionnidis JPA, et al. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion: The DIETFITS randomized clinical trial. JAMA. 2018;319(7):667-79.

8.            McClain AD, Otten JJ, Hekler EB, Gardner CD. Adherence to a low-fat vs. low-carbohydrate diet differs by insulin resistance status. Diabetes Obes Metab. 2013;15(1):87-90.

9.            Jirapinyo P, Devery A, Sarker S, Williams G, Thompson CC. Tu1931 – A Comparison of Diet Plan Outcomes in Diabetes Management: A Systematic Review and Meta-Analysis. Gastroenterology. 2018;154(6, Supplement 1):S-1057-S-8.

10.         Skeaff CM, Miller J. Dietary fat and coronary heart disease: summary of evidence from prospective cohort and randomised controlled trials. Ann Nutr Metab. 2009;55(1-3):173-201.

11.         Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. The American journal of clinical nutrition. 2010;91(3):535-46.

12.         Mente A, de Koning L, Shannon HS, Anand SS. A systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease. Arch Intern Med. 2009;169(7):659-69.

13.         Hooper L, Summerbell CD, Thompson R, Sills D, Roberts FG, Moore H, et al. Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database Syst Rev. 2011(7):CD002137.

14.         Zinn C, Rush A, Johnson R. Assessing the nutrient intake of a low-carbohydrate, high-fat (LCHF) diet: a hypothetical case study design. BMJ open. 2018;8(2):e018846.

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