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Ketogenic Diets in Review: How they work, bold claims, potential benefits & my thoughts.

Updated: Feb 11, 2019

Ketogenic diets seem to be doing the rounds again as the cool and trendy diet for max health and rapid fat loss.

In the brief time that I’ve been interested in health and fitness (4 years give or take a year) I’ve seen the keto trend surface at least 3 times. I dread to think how bored of it some long standing industry professionals must be. Nevertheless there is always new emerging data on keto as it’s popularity never seems to completely diminish.

I’m going to try and keep this one concise as there are a lot of points I’d like the touch on. Excuse the bluntness.

So, what actually is a ketogenic diet? True keto is around P20% C5% F75% or even higher on fats. Initially keto diets were as much as 90% fat.

There is a lot variation on where these % margins lie but in my opinion keto need to be:

  • Extremely low carb. 50g or less or 20g or less, depending on the person.

  • Some protein, but not too much (protein also creates insulin response).

  • High fat.

High protein diets are not ketogenic.

How does it work? Our body can use either fatty acids or glucose for energy, it has no real preference. It’s a chemical reaction the happens either way and the body will use what is there.

Glucose is the energy source our bodies primarily run on when we eat a mixed diet. When we eat carbs they are generally stored in the muscles and liver, via the signalling of insulin, as something called glycogen which is an energy reserve for the body to pull on when we need it.

Glycogenolysis refers to the breakdown of these glycogen stores in muscle and liver when we use them to maintain blood glucose levels during periods of fasting. This is happening between meals and when you are asleep, not just when intermittent fasting.

So how does this relate to keto?

If you take away carbs or go on a starvation diet/ fast the body will stop doing the aforementioned glucose energy system after a while and switch over to using something called ketones for energy.

This is because when we stop eating or remove carbs, we run out of stored glucose (glycogen) within 2-3 days, and have to find some other fuel source so that we don’t die. Enter ketogenesis:

Ketogenesis is the metabolic pathway that produces ketone bodies, which provide an alternative form of energy for the body. Ketones are produced in the liver. About 72 hours into starvation, ketogenesis is happening and we enter ketosis.

If you want to read more about how exactly we make ketones check out this article:

Is this healthy?

Some tissues (brain, muscles, liver + more) are conditional glucose users so can use either glucose or ketones for energy. Some tissues (red blood cells and CNS) are unconditional glucose users so they can only run on glucose. This means we need about 100g of glucose a day in order for these to function properly and us to live. Fortunately we can actually synthesise about 120g of glucose on our own without the need to eat carbohydrates. Glucose can be formulated from gluconeogenic substances (amino acids, triglycerides etc.) when needed, for example on a ketogenic diet.

So it’s not dangerous to be in ketosis and the body can function adequately using ketones for energy.

However, it does depend on how you define ‘adequate’ function.

Ketones can’t replace glucose in terms or anaerobic metabolism (high intensity stuff like HIIT and some weight training) but for aerobic work they are an adequate substitute for glucose. In my opinion being on a keto diet when you perform a lot of anaerobic activity is not optimal.

So, now that we know what keto is let’s look at some of the common claims surrounding it.

‘High fat intake isn’t bad for your cholesterol’

Anything consumed in excess has potential to be harmful. Even water, you can die from drinking too much water in one go. Eating a high fat diet is going to affect people differently. If a person wants to embark on a keto diet then learning the difference between saturated, monounsaturated and polyunsaturated fats is important in my opinion. Chronic consumption of high saturated fat intake can have the potential to raise LDL cholesterol and increase risk of cardiovascular diseases. Dunking huge blobs of butter and coconut oil in your coffee everyday might not be the best idea if you have family history of hyperlipidemia (high cholesterol).

‘Ketogenic diets are better for fat loss’

When calories and protein are matched both ketogenic and conventional diets report the same amount of total fat loss. There is no benefit to going keto purely for a higher rate of fat loss.

Some research on this topic:

‘Eat more fat = burn more fat’

Of course you are burning more fat, you are eating more fat, the net fat metabolism is higher. The same applies if you were eating more carbs. If you eat more carbs then you will burn more carbs, the net glucose metabolism is higher.

Fun fact: if you eat more fat, you will also store more fat. If you eat more carbs you will also store more carbs.

This does not translate to burning more body fat in either case unless calorie intake is controlled, i.e. you are in a caloric deficit.

Caloric deficit still rules, it doesn’t matter what ratio of fat to carbs you eat.

‘No insulin is released with keto so it’s impossible to store fat’ ‘Insulin = evil’ ‘HORMONES!!!’

A hormonal response to a surplus or deficit will never supersede the surplus or deficit. Calorie control still matters more than anything insulin can do whilst in a surplus or deficit.

Having high insulin responses whilst in a deficit isn’t bad or negative for fat loss. Having low insulin responses whilst in surplus isn’t disastrous for making gains either.

Caloric input rules. Hormones can respond to caloric input for sure, but hormones cannot alter or supersede the caloric input. Deficit or surplus drives hormones, it’s not the other way around.

It doesn’t matter HOW you create a calorie deficit as long as you make one if your goal is weight loss. If going keto means you can stick to your deficit each day or week, then this is fine.

‘Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize.’

‘I watched a documentary on it!’

Documentaries have no incentive to tell you the truth.

They are made purely to stir up interest and make money, shocking I know. If the goal of the documentary is to frighten your about your food choices how helpful is that really? That is fear mongering that takes advantage of the naive general public. Conveniently, these documentaries almost always provide you with a simple solution. In this case of ’The Magic Pill’ it’s to go keto and all of your ailments will be cured.

I am pro education but unfortunately the documentaries on Netflix misconstrue evidence to the point where it is no longer recognisable as fact in order to suit their own agenda. They are looking for a reaction so the claims made are highly sensationalist and are rarely backed up with reputable science.

Sorry to break it to you, but ’The Magic Pill’, ‘What The Health, ‘Forks over Knives’ and more were made for entertainment purposes, not to teach peer-reviewed science to the masses. Science is boring and complicated because it almost always doesn’t give clear, definitive answers. Boring doesn’t make for great TV. However claiming an extremely high fat diet can cure cancer and make you lose fat at a rapid rate is exciting and tempting to watch.

For context, there a full analysis here on every claim made in ‘What The Health’ and it turns out that 96% of the studies cited didn’t meet the claims that the documentary made. That’s pretty appalling as educational content in my opinion.

What about exogenous ketones?

We don’t have conclusive human studies or hardly any human clinical trials on this at the moment. I don’t think rodent trials are a good enough reason to start taking exogenous ketones.

What about sports performance?

Meh. I’ve seen nothing good yet.

Is it good for anything?

Yes. Potentially. I think these 3 things are worth looking into:


There is some evidence in rodent studies of ketones and ketogenic diets having a positive effect on tumour growth. There are a lot of different types of cancer so it’s not possible that keto could be a universal treatment and I think it’s too early to draw conclusions but it may worth talking to your Doctor about.


Recent research suggests that brain disorders like Alzheimer’s, Parkinson’s and other neurodegenerative diseases are related to metabolic disorders so ketogenic dieting could have potential for positive outcomes.

Please get medical supervision from someone other than Dr. Google if you want to try this stuff.



  • Don’t use a ketogenic diet or fasting alone to try to cure stuff.

  • Don’t go on a random keto diet just to ‘be more healthy’.

  • You don't need to go keto in order to lose bodyfat.

  • Please seek medical supervision from someone other than WebMD if you have any of the above diseases or conditions that may possibly benefit from a keto diet and want to try it out.

My thoughts on keto diets Negatives:

  • Ketogenic diets are almost always not sustainable in the long term and carry a high risk of weight regain.

  • Food selection is very restrictive.

  • It’s difficult to eat out.

  • Takes a while to adapt to ketosis, some people struggle more than others.

  • It’s not the optimal diet for those doing anaerobic training or who want to perform at a high level for strength.

  • It’s not the optimal for muscle building as insulin is primarily an anabolic hormone.


  • Potentially could be helpful if you have cancer, Alzheimer’s, epilepsy or some other diseases.

  • If ketogenic dieting helps a person achieve a calorie deficit when the goal is weight loss then this it is helpful.

  • Some people report higher levels of satiety on a ketogenic diet. If this increases dietary adherence then this is helpful.

  • Less movement in blood sugar levels. If this is important to you for a medical reason then it could be seen as beneficial.

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