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HomemifeatureDiet & Fasting: Taking Control of Diabetes

Diet & Fasting: Taking Control of Diabetes

Low carbohydrate, healthy fat diets are in the spotlight. In June 2017, optometrist Ryan O’Connor spoke to New Zealand’s Professor Grant Schofield about the science behind this approach to diet. This time round, he spoke to Dr. Caryn Zinn about the benefits of combining low carbohydrates and healthy fats with fasting.

Around the world, medical practitioners are promoting the long term health benefits of low carbohydrate, healthy fat diets. Dr. Gary Fettke in Australia,1 Dr. Shawn Baker in the USA,2 Professor Tim Noakes in South Africa,3 Dr. David Unwin in the UK,4 Virta Health in Silicon Valley5 and Dr. Jason Fung in Toronto,6 all advocate that lowering carbohydrate intake can lower blood sugar levels. Additionally, Dr. Fung pairs low carbohydrate, healthy fat diets with fasting in his Intensive Dietary Management Clinic,7 to improve the root cause of Type 2 diabetes – insulin resistance.

Closer to home in New Zealand, whole food dietitian and nutritionist Dr. Caryn Zinn has been clinically implementing fasting protocols with some of her patients. The great results she has been achieving inspired her new book, What the Fast?,8 which she co-authored with Prof. Schofield and chef Craig Roger. What the Fast? follows on from their first two books, both titled What the Fat?

Dr. Zinn advocates the philosophy of ‘live long, drop dead’

I was lucky enough to interview Dr. Zinn about fasting. The knowledge she shared provides a powerful tool that I believe we can use to improve our own health and to help our Type 2 diabetic patients manage their condition in an effort to reduce the risk of complications such as diabetic eye disease.

Dr. Zinn advocates the philosophy of “live long, drop dead”. In essence, she believes we should all live for as long and as well as we possibly can without experiencing a “fading tail end” of chronic disease supported by medications.

Fasting fits into this mantra in two ways. Firstly, it helps to prevent chronic conditions by reducing weight, improving our glycaemic response, and reducing inflammation. Secondly, fasting may help extend our lives via improved cellular repair, nourishing our brain, and optimising our immune system.


To be successful in fasting, it’s wise to start by adopting a low carbohydrate, healthy fat diet. When a person becomes ‘fat-adapted’, their body is used to burning fat as a fuel source, whether it comes from food or the body itself. Missing a meal when a person is fat-adapted means they can carry on doing what they’re used to doing with relative ease – their body simply gets its energy by burning stored fat.

However, if a person’s body is predominantly used to burning carbohydrates, missing a meal will be more difficult and will ‘hurt’. That’s because, rather than acquiring the energy it needs from carbohydrates, the body will need to learn to burn stored fat.


You’d expect that prolonged fasting would make us feel hungrier, however this is not the case because when a person fasts, their ‘hunger hormones’, otherwise known as leptin and ghrelin, soon kick in. Leptin is a hormone, made by fat cells, that decreases appetite. Ghrelin is a hormone that increases appetite, and also plays a role in body weight. By combining a low carbohydrate, healthy fat diet with prolonged fasting, ghrelin levels are lowered and the body and brain tend to become more in tune with cues for hunger and fullness.


Our circadian rhythms tell us that we are least hungry in the morning and most hungry in the evening. What the Fast? proposes the super-fasting protocol, i.e. we should miss morning and daytime meals and eat meals at night when we’re naturally at our most hungry. Additionally, What the Fast? suggests we do this on Mondays and Tuesdays.

Fasting on Monday and Tuesday, while eating ‘super-meal’ dinners, will allow the body to either approach or get deeper into nutritional ketosis; the state in which it burns fat as its primary fuel rather than glucose (sugar).

Dr. Zinn suggests that “low carbohydrate, healthy fat eating is called ‘fasting mimicking’ because it allows the body to keep burning fuel from fat (because carbohydrates are kept low), which means nutritional ketosis is maintained throughout the week until such time as the person eats more carbs”.9


Nutritional ketosis is a normal and natural state in which the brain is using ketones (the breakdown of fat) as a fuel source. “We know that in brain related conditions, there is a defect in the metabolic pathways of glucose utilisation, so by supplying the brain with a different fuel source, we are likely to bypass the defect,” she says.10

As well as producing ketones to fuel the body, fasting stimulates production of Brain Derived Neurotrophic Factor (BDNF) – a protein that can be thought of as ‘brain fertiliser’ according to Dr. Zinn.11 BDNF assists with the development of new connections; can help repair dysfunctional brain cells; and protects healthy brain cells from damage. Having enough BDNF around can protect our brains from neurodegenerative diseases like Alzheimer’s and Parkinson’s disease.12

Additionally, in essence, fasting reboots the immune system, regenerates white blood cells, and replenishes any blood cells that have been lost.13Fasting may boost the body’s natural defences against inflammation by reducing proinflammatory cytokines and immune cells, and inhibiting inflammatory pathways. Indeed, studies have shown that inflammatory biomarkers, such as CRP and some of the interleukins, are reduced by fasting. This has implications for the management of a wide range of immune system deficiencies, such as autoimmune disorders (e.g. multiple sclerosis and fibromyalgia), rheumatoid arthritis, inflammatory bowel diseases, and chronic fatigue syndrome.14

Dr. Caryn Zinn


Fasting increases the rate of insulinmediated glucose uptake.15 In other words, it allows the cells to become more responsive to insulin, which means blood sugar levels are lowered and the amount of insulin required is reduced, in turn reducing insulin resistance. Eating low carbohydrate, healthy fat whole foods goes one step further by ensuring that when we eat, insulin levels remain low throughout the day.

A glucose meter, which highlights the foods that drive up glucose and effect insulin resistance, is an effective tool that your diabetic patients can use to enhance their understanding of the impacts of different foods. The ability to self-test for glucose tolerance using a glucose meter, combined with testing blood glucose levels (HbA1c), will provide them with a indicator of their level of insulin resistance.

Suggest to your patient that they measure their blood glucose before a meal and then after a meal, to see what foods raise their blood sugar (e.g. low carbohydrate vs. carbohydrate based meals). Then, by remeasuring their blood sugar two hours after the meal, they can see the foods which continue to raise blood sugar levels, due to their ineffective insulin response, and those which have a lesser effect on their blood sugar.

In the long run, by choosing lower insulin requiring foods (a low carbohydrate, healthy fat diet) and improving their insulin sensitivity through fasting, your diabetic patients should achieve better HbA1c outcomes, which in turn should reduce the risk or progression of associated complications such as diabetic retinopathy.16

Prevalence of Diabetes and Diabetic Eye Disease 

In New Zealand, 6.5 per cent of the population above the age of 25 are affected by Type 2 diabetes, with the prevalence among Pacific Islanders the highest at 14.5 per cent and Maori at 9.1 per cent.1

In Australia, diabetes is the fastest growing chronic condition; increasing at a faster rate than other chronic diseases such as heart disease and cancer. All types of diabetes are increasing; an estimated one million Australian adults (5 per cent) had Type 2 diabetes in 2014–15, according to self-reported data.2 Proportions were around twice as high in the lowest socioeconomic group (8 per cent) compared with the highest socioeconomic group (3 per cent).3

Diabetes is also the leading cause of preventable blindness in Australia.4 There are currently around 72,000 people in Australia with diabetic retinopathy, with approximately three in five experiencing poor sight.4Diabetic retinopathy occurs in over 15 per cent of Australians with diabetes.

The total indirect cost of vision loss associated with diabetic macular oedema in Australia is estimated to be AU$2.07 billion per annum. This is more than $28,000 per person with diabetic macular oedema.


1. Annual Update of Key Results 2015/16: New Zealand Health Survey, Ministry of Health, Published online: 15 December 2016, Sourced online 12/3/2017, health.govt.nz/publication/annualupdate- key-results-2015-16-new-zealand-health-survey 

2. Australian Diabetes Data sourced from the Australian Government, Australian Institute of Health and Welfare Website which sites the ABS 2014–15 National Health Survey, Sourced online 12/3/2017,. aihw.gov.au/how-common-is-diabetes 

3. The Economic Impact of Diabetic Macular Oedema in Australia, Bayer Australia Ltd, April 2015, Performed by Deloitte Access Economics, Sourced online 12/3/2017, mdfoundation.com.au/ resources/Final_report_Economic_Impact_of_DME_ in_Australia.pdf 

4. Socioeconomic cost of macular degeneration in New Zealand, Macular Degeneration New Zealand, 17 October 2016, Performed by Deloitte Access Economics, Sourced online 12/3/2017, mdnz.org. nz/assets/Deloitte-MDNZ-Cost-of-AMD-FINAL-17- Oct-2016.pdf 


The current guidelines suggest that most people need to eat several times a day – and in fact, every two to three hours17 – which has them constantly in a state of feeding the cells (anabolism or growth). However, the body’s cells need time to rest for self-repair and healing, and that means not feeding them from time to time. In practice, Dr. Zinn has seen how calorie reduction via fasting is much easier to quantify and is likely to be safer for the body’s metabolism long term. By going for long periods of not eating and then eating, the body is kept guessing – and it doesn’t think it’s starving.

Continuously restricting energy intake may indicate to the body that it is consistently receiving less and less energy over time (i.e. approaching starvation). This could result in the body’s hormones behaving in such a way that signals danger, causing them to take action to preserve weight (thyroid is a good example of this).

Five Facts For Fasting 

1. Start low, go slow: eat low carbohydrate, healthy fat foods and become accustomed to using fat for energy.

2. If a 24 hour cycle is too much, start with a smaller intermittent fast by missing breakfast, or eat earlier in the day and miss lunch or dinner.

3. Know why: Hunger and offers of food can be tempting, however, for people with Type 2 diabetes in particular, it is important to maintain the course; diabetes is a chronic and deteriorating condition; with a disciplined approach to diet, it doesn’t need to be that way.

4. Don’t over think it: simply don’t eat for an extended period

5. Monitor your weight and, if you have diabetes, your markers as well. 


It is true that exercising helps burn stored glucose and increases the local muscle insulin sensitivity, but as the saying goes: “You can’t out-run a bad diet”, and typically, if someone is insulin resistant, they have painful joints from inflammation, and are often over weight. This will restrict their interest in, and ability to exercise. Fasting’s anti-inflammatory effects and ability to help lose weight may make exercise more accessible for patients who may already be struggling to get out and partake in some form of exercise.


For low carbohydrate food ideas, check out some of the recipes from chef Craig Roger on the What the Fat? blog including; the salmon and green tea poke (Dr. Zinn’s favourite super meal), low carb sausage rolls, egg rolls, meatballs and koftes, egg cups, and of course New Zealand’s famous, low carbohydrate pavlova.18


People who take sulphonylureas to manage their diabetes mellitus Type 2, such as Glipizide and other insulin promoting medications, as well as those using insulin, must only modify their diet while under strict medical supervision. Additionally, these patients must be cautious about the dose of sulphonylureas they take as it may cause hypoglycaemia. However in the long run, a protocol of consistent fasting and a low carbohydrate healthy fat diet can enable many patients to be weaned off these medications. For this reason, nephrologist Dr. Jason Fung is passionate about fasting coupled with the low carbohydrate, healthy fat diets. He, like other low carbohydrate practitioners throughout the world, is showing that Type 2 diabetes is able to be put into remission. For Dr. Fung this means fewer patients on dialysis; for Dr. Fettke and Baker, it means less lower limb amputations, and for Dr. Unwin it means less cost to the National Health Service in the United Kingdom. Professor Noakes is able to manage his own Type 2 diabetes and for us, as eye health professionals, it means less anti-VEGF and laser, slower onset of cataracts, and less irreversible blindness.

Ryan O’Connor is an optometrist with Headwear in Ballina and Casino, northern New South Wales. He completed his Bachelor Degree in Optometry from the University of Auckland in 2013, following a Bachelor of Science in Anatomy from the University of Otago in 2009. As part of his Science degree he sat papers in functional, reproductive and neuro anatomy, applied physiology, zoology and sports nutrition. A keen rugby player, Mr. O’Connor takes an interest in sports performance and nutrition and drives his endeavours into the field of sports vision. This is complemented by his passion to improve the lives of young children.


1. www.isupportgary.com/articles/enough-isenough- dr-gary-fettke 

2. www.youtube.com/watch?v=Yj_Bc9hdHa0 

3. www.news24.com/SouthAfrica/News/judgmentreserved- in-tim-noakes-appeal-20180223 

4. www.diabetes.co.uk/blog/2015/08/dr-david-unwinpublishes- more-evidence-of-low-carb-diet-benefits-in-the-bmj 

5. www. blog.virtahealth.com/one-year-clinical-trialoutcomes- type-2-diabetes/ 

6. www.dietdoctor.com/authors/dr-jason-fung-m-d 

7. www.idmprogram.com/ 

8. www.whatthefatbook.com/product/what-the-fast 

9. www.youtube.com/watch?v=8BYvHgs-oww 

10. www. ncbi.nlm.nih.gov/books/NBK209323 

11. www.nrcresearchpress.com/doi/abs/10.1139/apnm- 2014-0290#.Wufiu9NuagQ 

12. www.sciencedirect.com/science/article/pii/ S0166223604002589 

13. www.sciencedirect.com/science/article/pii/ S1934590914001519 

14. www.ncbi.nlm.nih.gov/pmc/articles/PMC5682732 

15. www.idmprogram.com/fasting-physiology-part-ii 

16. www.diabeticretinopathy.org.uk/prevention/hba1c_and_ retinopathy.htm 

17. www.health.govt.nz/our-work/eating-and-activityguidelines/ current-food-and-nutrition-guidelines 

18. whatthefatbook.com/recipes