Understanding The Ketogenic Diet – A Critique.

I have come across so many articles over the years regarding the infamous ketogenic diet. Some have been informative, some have been speculative, and some have been so riddled with misinformation that I don’t know whether to laugh at how comical it is, or cry at how misleading and dangerous it is – as dangerous as these people claim the ketogenic diet to be.

Recently, I have come across an article in the Huffington Post, discussing the ketogenic diet. It seemed to be a rather matter-of-fact article, with a prominent Australian researcher dietitian being interviewed.

What they failed to mention was that this prominent Australian researcher dietitian has vocally condemned low carb nutrition and the ketogenic diet on multiple occasions in a public forum, and is a staunch defender of the Australian Dietary Guidelines, so I wasn’t holding my breath when I read this article.

Unfortunately, as predicted, as I read on, more and more problems jumped out at me, and I couldn’t resist but put some of these bogus arguments to bed. It confuses me how someone who is supposedly one of Australia’s leading researcher dietitians can ignore #RealScience in favour of what I can only describe as “science” that #LooksLikeRealScience but isn’t.

As per my usual style, I have quoted verbatim from the original article found here, and have written my views below.

What is a Ketogenic Diet?

Clare Says: A ketogenic eating pattern is very low in carbohydrates and moderate in protein, meaning a high percentage of total energy intake comes from fat found in dairy products and meat.

A true ketogenic diet is one where carbohydrate intake is extremely low- usually less than 10 percent of your total energy intake.

I say:
A ketogenic diet is definitely characterized by a low carbohydrate, moderate protein and high fat macronutrient split.

How low the carbohydrate intake needs to be, however, varies from person to person, stage to stage of keto-adaptation, and depends heavily on hormonal status and carbohydrate tolerance. To say that a “true” ketogenic diet has less than 10% total intake from carbs is ignorant, because the automatic assumption is that anyone who is in ketosis on a higher carb split is in “fake” ketosis.

The other thing is the assumption that the fats consumed on a ketogenic diet come from dairy and meat. Sure, some do, but most people on a ketogenic diet also consume olive oil, coconut oil, avocados and nuts – none of which are “dairy” or “meat”.

How does a ketogenic diet work?

Clare says: During times of severe energy restriction (such as during fasting or starvation), prolonged intense exercise, or when carbohydrate intake is reduced to around 50 grams per day or less, the body can enter ketosis.

This means that, rather than the body burning its primary fuel source, glycogen (a complex carbohydrate, which in the human body is like petrol for a car), the body must break down fats as its main source of fuel.

If you can flip the switch and get the body to burn predominantly fat, then you produce these things called ketone bodies, which can appear on your urine and they also come out on your breath. They actually smell like acetone, like nail polish remover essentially.

I say:
A ketogenic diet aims to get people into a state of ketosis, where the body is primarily oxidizing fats for fuel. These “things” that our Prof talks about are actually by-products of fatty acid oxidation, called ketones – a water-soluble molecule that can cross the blood brain barrier to act as direct fuel for the brain when glucose is limited. Whilst you certainly can detect ketones in urine and the breath, by far the more reliable and accurate way of measuring ketones are via the blood.

Whilst it is all good and well for us to sit here and wax poetic about likening glycogen to “petrol”, the truth of the matter is, you wouldn’t use petrol in all engines. If we are to entertain our Professor and use her analogy of petrol, then we need to look at it this way – sure, glycogen is like petrol, but not all cars were made to function optimally on petrol. If you start feeding a diesel engine petrol, you are going to run into a lot of problems. This is fundamentally the problem we have today. Some people function quite well on a higher carbohydrate diet – they are metabolically flexible, quite carb tolerant, and have no issues with eating more carbs. In these cases, sure, eat more carbs. However, when you have someone who is insulin resistant, carb intolerant and don’t tend to function well with carbs (Type 2 diabetics fit perfectly into this realm, for example), the solution is not to keep feeding them copious amounts of carbs, regardless of how low the GI is. In this case, we need to promptly recognise that for these guys, their “engine” takes diesel, and we need to swap over to diesel, or we risk killing the “engine”.

Our Prof also seems to be fiercely ignorant and appear to doubt the body’s ability to “flip the switch”, but the truth of the matter is, if our Prof actually understood the #RealScience, she will know that whilst it may take some time to metabolically adapt over, fat adaptation is a sure thing that can be replicated time after time. How do I know this? Because #RealScience.

How Many Carbs Can You Eat And Still Be In Ketosis?

Clare Says: “In terms of grams, it’s somewhere between 20 and 50 grams of carbohydrates a day. To give you an idea of how much that is, one typical big slice of bread from the supermarket has about 20 grams of carbohydrate.”

In a 50 gram carbohydrate diet, you might have a piece of fruit, a slice of bread and a small potato across the day.
“That’s it in terms of foods which are good sources of carbohydrate, and the rest would come from the incidentals you’d find in milk and salad-type vegetables. It’s extremely strict,” Collins said.

“The true, original ketogenic diet can be anywhere from 80 to 90 percent fat, so they really should be considered as medical nutrition therapy. To be used at that level, you really need close monitoring.”

I say:
To be really honest – the real answer to this question is “as much carbs as it takes to still keep you in ketosis”.

For some people this may be 20g, others it may be 50g, but I also know that for some it is 90-100g.

However what we need to look at here are 2 things:
1. Total VS Net Carb
2. Carb quality

When we talk about carbohydrates, we need to look at the fibre content of these foods. Fibre is indigestible, meaning that it resists digestion, and does not ultimately contribute to overall carbohydrates that get broken down in the body. Usually when we talk about carbohydrates in the context of ketosis, we talk about “Net Carbs”, which is “Total Carbs minus Fibre”.
When the Prof gave her example of what 50g of carbs a day looked like, she mentions a piece of fruit, a slice of bread and a small potato a day.

Food Total carb Fibre
A medium apple 25g 4.4g
A slice of bread, wholegrain 12g 1.9g
A small potato 30g 3.7g
TOTAL 67g 10g
Net carb


When you look at that, you think “omg that’s NOTHING! If I eat ANY veg, it will blow my daily limit way over!”

But the truth is, no one who is actually serious about keto would ever opt for any of those foods to be part of their diet. Instead, they would choose nutrient dense, fibre-rich foods, as this not only ensures nutritional adequacy, it also means they get to eat a LOT of food.

Now let’s take a look at how it is actually done:

Food Total carb Fibre
Green beans 100g 7g 3.4g
Zucchini 1 medium 6g 2g
Broccoli, 1 cup 6g 2.4g
Spinach, 100g 3.6g 2.2g
Silverbeet 100g 3.7g 1.6g
Avocado 1 whole 17g 13g
Raspberries 1 cup 15g 8g
TOTAL 58g 32.6
Net Carb 25.4g

What you can see here is that even after close to 1kg of vegetables and berries, your net carb is ONLY 50% of the “50g” our Prof keeps talking about. Being a DAA spokesperson, our Prof’s stance on nutrition is “plant based is best” – well, not going to lie, 2 kilos of “plant based foods” a day is pretty darn plant based to me!

Furthermore, what nutrients do a piece of fruit, a slice of bread and a small potato offer that 2 kilos of different vegetables and fruits don’t offer?

Absolutely NIL.

Even if we were to lower carbs for those who need to consume less to achieve ketosis, the above example illustrates that with a combined 1kg of vegetables and some fruits, this is still achievable, without compromising variety or quantity of food.

So, remind me again how a ketogenic way of eating is all “meats and dairy” and “restrictive” again?

C’mon Prof – I find it worrying that a professor in dietetics would attempt to wilfully mislead the general public into believing that low-carb is restrictive and meat-based. However, if it isn’t wilful misleading, it concerns me more that a professor in dietetics doesn’t already know this information. Either way. I am concerned.

How Do You Know If You Are In Ketosis?

Clare says: While it depends on “many individual variability”, the time it takes to burn fat and produce ketone bodies is typically about three days of carbohydrate restriction, or three days of severe total food restriction, Collins explained.

“The way you find out if you’re ketogenic (if you’re producing ketones) is you buy keto test strips at the chemist and you test your urine.”

I say:
Yes, there is a lot of individual variability – like hormone levels, metabolic health, current dietary intake, et cetera that can affect how quickly or slowly someone gets into ketosis. However “blowing” (as per previous reference of nail-polish breath) or “peeing” ketones is not exactly the same as burning fat for fuel as is evident in those who are properly keto fat-adapted.

Let me explain.

Ketones are by-products of fatty acid oxidation. Our bodies produce ketones routinely when the liver breaks down fat. However, the production of ketones alone is not suggestive that the body has switched over to using fat as its primary fuel. When we talk about the physical, mental and metabolic benefits of ketosis, we are actually talking about the benefits as seen in those who are properly fat-adapted. This is something that can often take weeks to months to properly achieve.

So, quite apart from the fact that the Prof assumed that “producing ketones” equated to being “ketogenic”, she also made the grave mistake of assuming all forms of testing are equally reflective of being ketogenic, and finally makes a fly-away comment about how buying keto test strips to check urine ketones will suffice in concluding whether or not someone is in ketosis.

If the Prof looked into the #RealScience further she would have realised that there are in fact 3 different ketones – acetone, acetoacetate and beta-hydroxybutyrate. Of these 3 ketones, acetone is what is detected in the breath, and is a ketone that results from breaking down acetoacetate. Acetoacetate is usually detected in the urine, and is excreted in this method when there are excessive ketones in the body.

When you test urine, blood and breath ketones you will see that there is very minimal correlation between rising or falling blood ketones, and that of urine and breath ketones. Further to this, urine ketone levels decrease as someone becomes more and more fat adapted, as their body will become more efficient at using ketones, instead of just peeing it out.

Because of these subtleties, we believe that blood ketone readings to assess the level of beta-hydroxybutyrate is typically the best way to assess ketosis. As per Phinney and Volek, nutritional ketosis is achieved when blood ketones are consistently sitting between 0.5-3.0mM. Whilst ketones can be safely higher, it isn’t always better or even necessary.

The Pros of a Ketogenic Diet

1. Effective short-term weight loss

Clare says: According to the Dietitians’ Association of Australia (DAA), following a ketogenic diet will “undoubtedly result in short-term weight loss” which probably comes down to a few factors:
• A reduction in total kilojoule intake
• The depletion of liver and muscle glycogen stores and associated water
• A reduced appetite(which is a side-effect of metabolising ketones, and also due to satiety associated with eating foods containing fat and protein)

I say:
Not going to lie – the DAA is not a very reliable place to be quoting anything on the topic of low-carb or ketogenic nutrition, considering the DAA still believes that saturated fats cause heart disease, and low carb diets are fads. When you jump onto the DAA website and browse through their list of Hot Topics, you can see just how mislead they still are when they desperately try to stamp authority on topics that they frankly have no authority over. The most comical part is how they are constantly trying to convince the general public to see an APD (which I am one, by the way) on topics that they show no leadership, understanding or even openness towards – yet, apparently, they are still the go-to experts? Frankly I am a bit embarrassed by that, especially when their go-to alternative is the Australian Dietary Guidelines, which still to this day believe that saturated fats are found in commercial biscuits and cakes.

My point is further substantiated in the fact that the DAA believes that a ketogenic diet works because of a “kilojoule reduction”. Last time I checked, the entire premise behind the ketogenic diet was a change in macronutrient ratio – not a kilojoule deficit. In fact, in most cases, if one was to simply swap out their carbs for fats, gram for gram, they will in actual fact end up with more kilojoules. At no point is it suggested or even recommended that this way of eating needs to be (or even should be) a kilojoule reduction.

Also – for everyone who has ever tried to cut calories when eating a “portion controlled” diet, the number one complaint is that they are always hungry. So, again, not going to lie, if someone was able to feel more satisfied, eat plenty of food, and lose weight, I hardly see that as a negative thing that our Prof makes it out to sound.

2. May help to manage epilepsy in children

Clare says: if you have a child whose seizures are so severe and frequent, no medications are working, have frequent accidents and need to wear helmets to protect their heads, then of course you would try it. This is why it’s quite annoying how flippantly the ketogenic diet is being discussed as “hey, yeah, let’s go keto”.

I say:

Hold. Up.

So, what I am hearing you say here, Prof, is that there is a diet made up completely of natural, real, whole foods that can fix a debilitating condition and return to someone their quality of life that no medication with a staggering list of side effects can achieve; yet – you don’t see the wonder in how food has effectively trumped medicine in this circumstance, and instead of then realising how this natural and non-invasive way of eating should be the first line approach, you taunt at it like it is a crappy last-resort?

Can we not see the irony in all this?

Also – if currently dietary protocols are so effective at improving the health of the population, why would so many people so “flippantly” decide to try a ketogenic diet and realise through the process that all their joint pain has gone, their brain fog has disappeared, they no longer think about food all day long, their energy levels are better, their mood is better and the weight that has been accumulating around their midsection has now successfully come off, allowing them to realise that they aren’t just getting older – but they were in fact getting sicker, something a change in diet and metabolic pathway via the ketogenic approach has helped them fix.

Something that if only you would read more into, instead of just applying your hard-wired confirmation bias against, you would realize is grounded in #RealScience, unlike the ADGs which you blindly push, which at best only #LooksLikeRealScience.

3. May have positive effects in the treatment of some cancers

Clare says: “I will preface this with: do not try this at home,” Collins said.

“There is research, predominantly in animals studies, looking at the use of the ketogenic diet for optimising outcomes during cancer treatments. This is absolutely medical nutrition therapy at its highest level. If you throw yourself willy-nilly onto a ketogenic diet during cancer treatment, you risk becoming malnourished.

I say:

Look – I won’t disagree in that the effect of a ketogenic diet on cancer is currently not well established, and that a ketogenic approach is definitely considered medical nutrition therapy in the context of cancer treatment. However, I do not believe that following a ketogenic diet during cancer treatment will lead to you being malnourished. The only reason anyone would think that is because they fundamentally think that the ketogenic diet is malnourishing, which is simply not true.

The cons of the Ketogenic Diet

1. It can lack phytonutrients, fibre and B-vitamins

Clare says: Due to the carbs found in many fruits, vegetables, whole grain and legumes, these healthy, high-fibre foods are extremely limited, which can lead to issues such as constipation and nutrient deficiencies.

“What concerns me about the people who are absolute purists on the ketogenic diet, is it means you’re cutting out groups of food which offer a lot of protection — namely vegetables providing phytonutrients and fibre which help with bowel cancer and managing body weight,” Collins said.

I say:
The truth is, there are extremists in all different styles of eating, and extremism is not what we promote, no matter what it is in the context of.

Even “healthy eating” at the most extreme has been dubbed “orthorexia” and is not encouraged.

However, when we talk about the ketogenic diet, it is important we look at it in a very objective way, based on it being a macronutrient manipulation to assist those, who would benefit, enter into a state of nutritional ketosis. When we look at what a typical person would do on a well-formulated ketogenic diet, plant-based foods like vegetables, avocados, nuts and plant oils such as coconut oil and olive oil are encouraged and consumed in abundance. Well sourced, quality meats, fish, poultry and eggs are also encouraged, as are some dairy products such as cheese.

When you look at the ketogenic diet objectively, you will realise that it is a diet rich in phytonutrients, fibre (as we have sufficiently demonstrated in my earlier example) and B-group vitamins. In fact, I cannot think of a single nutrient that “wholegrains”, breads, pastas and high-sugar fruits offer that cannot be met on a ketogenic diet, and I hereby challenge the Prof to come up with one herself.

2. Can affect gut health

Clare says: As well as helping to fill us up, fibre is vital for a healthy gut, such as supporting the growth of ‘good’ bacteria and keeping the bowel lining healthy. With Australians on average already not meeting the recommended daily amounts (25g of fibre for women and 30g for men), a ketogenic diet will make it harder to meet these targets.

“Long term, coming back to a dietary pattern which allows them to eat whole grains, lots of vegetables and fruit is what’s best for their overall health and wellbeing,” Collins said.

I say:
Firstly I need to point out (again!) that a ketogenic diet is not void in fibre. Based on our earlier calculations, if you were to go by “50g of total carbohydrate” you will still be able to consume 30g of fibre, which according to our Prof, is meeting the fibre needs of both men and women. Furthermore, this works out to be less than 25g of net carb a day – so, if you were to double the carbs to make up 50g net carb, you will be consuming TWICE the amount of fibre that our Prof deems necessary for “gut health”.

However, as we understand the gut better, we know that the indigestible fibres feed the gut by fermenting in the large intestine to short chain fatty acids. Funnily enough, butter and cheese are two of the richest dietary sources of butyric acid, a short chain fatty acid.

So, the only way I see that a ketogenic diet affects gut health is in a positive way, providing ample sources of short chain fatty acids to fuel healthy gut microbiota.

3. It’s not sustainable

Clare says: One thing the ketogenic diet ignores is that not all individuals will benefit from, or even require, the diet — nor is it sustainable for the long term.

As the DAA explained: “The key to maintaining a healthy weight in the long-term is an eating pattern that is sustainable over time. With this in mind, dietary recommendations should always be tailored to an individual — as everyone is unique, and what works for one person, may not work for another.”

“You’re not going to have much joy eating on a ketogenic diet. You’re going to have sticks of celery with cream cheese for snacks and bacon and eggs for breakfast, but there won’t be any warm toast or flavours from a range of vegetables, fruits and legumes,” Collins added.

Other short-term side effects of ketosis can include fatigue, bad breath, nausea and headache.

I say:
Lucky for the general public, the DAA is not the one doing a ketogenic diet – therefore it is completely not up to them or the Prof to decide what is, and what isn’t sustainable long term for each individual of the public.

The worst part of this entire statement is the Prof’s petty attempt to convince the reader that breads, fruits and legumes are more palatable and inviting than bacon, eggs and cream cheese. Worst still, she throws in some short term side effects to completely deter someone from thinking keto is a good idea – I mean, nobody wants short term nail-polish breath…right?


The part that riles me up the most really is the fact that The Huffington Post decided to write a feature on the ketogenic diet – however the tone was set from the get-go that this was one not in favour of the ketogenic diet. Not only did they use all journalistic attempts to make keto sound like the worse-off cousin to the ADGs, they also interviewed the Prof, one of the most well known anti-low carb dietitians the country has seen.

There are so many experts who would have done a much better job; so many individuals who have such inspiring stories of their own health journey with keto to share – yet, a dietitian that more or less calls the ketogenic diet an unsustainable, nutrient poor fad was the one chosen to talk about a topic she has no personal experience with, and by the looks, no #RealScience knowledge on.

Feng-Yuan Liu

Feng-Yuan Liu is the Founder, CEO and Senior Dietitian of Metro Dietetics.