Nutritional Ketosis – consequences of a high fat diet

Before I embark on this post, I would just like to say that Burn & Learn in no way endorses nor seeks to discredit ketosis as a pathway to achieving success with our three key concepts – food, fitness or fulfilment.  The following article simply aims to describe our experience with Nutritional Ketosis. Having said that, taking dietary fat to the extreme honestly brought nothing but suffering for Naomi and myself, and for the first time in many years I felt like I’d lost my nutritional marbles.  What we hope you will get from this article is that it urges you to think long and hard about potential benefits and possible negative consequences of undertaking diets that could be considered ‘extreme’.

So where did this all begin?  Well, after reading many fabulous paleo-esque books that went against standard dietary concepts and promoted the benefits of incorporating full fat in one’s diet, Naomi and I were ‘primed and ready’ to hear about ketosis – a dietary approach where you consume more than 70% fat each day.  So… knowing how well avoiding grain worked for me in the past, I was intrigued to hear that there was a controversial diet approach that would cause glucose levels to drop so low that my body would switch to using (and burning) fat instead. Ignoring for a moment the importance of micronutrients in one’s diet – I was keen to explore this strange concept of rearranging the standard dietary macronutrient structure. So I started as everyone does these days by ‘googling’ the word ‘ketosis’, and from the enormous amount of material I found online, it appeared that the potential, dare I say miraculous, benefits of this otherwise little know approach were widely proclaimed and rarely, if at all, denounced.

Being of above-average health and fitness, without any diseases (as far as I’m aware), I’ll admit that ketosis appealed mostly to my vanity.  From what I read, in 6 short weeks I’d have shed my winter layers and rock a bikini like never before.  In addition, my energy levels and mental clarity would be through the roof. I was so convinced of its merits and believed that I may well blow the lid on a global conspiracy designed to keep us fat and sick.  The people charged with giving us dietary advice, recommending silly things like 6 servings of grain a day, when all the while we could have been eating limitless butter, pork belly and triple cream brie!?

Gripping to a small shred of my sanity…. I did find myself pondering…. this is in complete contradiction to my usual philosophy about wholefoods and ‘balance’. How can fruits and vegetables be so bad?  Were they really so hard to come by as a caveman? Is there really a magical ‘hunger switch’ which can be turned off by eating fat?  Can you really strip kilograms so effortlessly?  Was there really a global conspiracy?

After many hours researching, I was convinced that cream, butter and bacon had been unfairly demonised and deserved another chance.  I recruited my food and fitness partner-in-crime Naomi to road test this hypothesis. We agreed to spend 6 weeks using our bodies as experimental fat reciprocals, ingesting a daily intake of over 75% fat and less than 15% carbs.  We agreed to take the findings to the people by creating a blog.

Some keto dishes are actually quite delicious (

Some keto dishes are actually quite delicious (

Some basic theory

So before I get stuck into fat, let’s start with glucose.  It would be a great idea for you to read this Guide to Carbohydrates by Wellness Mama.

Our bodies run rather efficiently on glucose.  It’s the primary source of the energy to complete a university assignment or climb a flight of stairs. The trouble with the world’s weight and health issues is not glucose per se, glucose is perfectly safe if you do not exceed your body’s energy requirements. However with a western diet full of cakes, biscuits, bread, pastas, sodas and the like, along with sedentary lifestyles, it becomes easy to see that we are in constant danger of stressing (or breaking!) the coping mechanisms of our bodies.

So…. in a nutshell… having too much glucose in our systems causes our glycogen receptors to become full and our bodies have no choice but to store this excess energy as fat.  It doesn’t matter the source of the glucose once your body hits its threshold…. carbs and sugars from any source (even those you believe to be nutritious) will store as fat.

So what is Nutritional Ketosis…..

Nutritional Ketosis takes place when you carefully control your macronutrient intake so that you have a very high proportion of fat in your diet.  By eating mostly fat and very few carbs you deprive your body of glucose and hence your body will then switch to burning ketones (produced by the liver) as a fuel.  Before you warn me it’s dangerous, remember that blood ketone levels in nutritional ketosis are between 0.5 and 3.0 mMol/L (whereas diabetics who experience ketoacidosis are actually around 15 to 25 mMol/L).  For more information on this, read Peter Attia’s post on Is Ketosis Dangerous? Nutritional Ketosis is also championed as a healthful state for the body by a range of highly regarded low-carb experts (Read Steve PhinneyJimmy Moore and Fat Head Blog).  Joseph Arcita outlines a host of benefits to this fat-full approach, including:

  1. Better mental focus
  2. Lowering of cholesterol
  3. Benefits for sufferers of Type 2 diabetes, hypertension, alzheimers and various cancers
  4. Better cardiovascular health
  5. Preservation of lean body mass
  6. Loss of body fat
  7. Blunting of appetite and increased satiation

The Keto Experiment…

In a nutshell the Keto experiment that we set ourselves was to embark on 6 week controlled diet comprising approximately 1500 kcal per day of which more than 75% was to come from fat.  Some of our favourite food options were now off the menu – including most fruits, chocolate, sugar, yogurt and even 80% of vegetables.  We would both have to embrace the concept of full fat cream, butter, low carb vegetables and only the smallest smattering of low carb fruits.

A typical keto-style meal - as much fat as possible!

A typical keto-style meal – as much fat as possible!

The table below shows the difference between your options on full fat versus good carbs.  This hopefully puts it into perspective that we were faced with some serious challenges to reduce portions, increase fats to uncomfortable levels and show some of our favourite fruit and vegetables the door.  Yes, it’s true that fats are more satiating than carbs, however the learning here is that you can have a few wedges of cheese or 2 plates of broccoli!!!  I’m sorry – but you can preach about fats all you like… 2 plates beats 2 wedges.

Full Fat Lean Protein Bad Carbs Good Carbs
(each option below represents approx. 300 kcal)
3 tablespoons of full fat butter 250 gram porterhouse steak no fat 2 potato cakes fried 1.3 kg of cauliflower
3 wedges of camembert cheese 200 grams of poached chicken breast 1 slice of chocolate cake 15 cups of zucchini
2 fried eggs with 1 strip of bacon 250 grams of steamed fish 1 small packet of Red Rooster Chips 6 cups of strawberries

Any good experiment requires data, so to provide us with something to analyse we decided we would monitor our biomarkers and general body measurements, record how we felt and make observations regarding our relative levels of hunger/satisfaction.  We were convinced that by the end of the experiment we would blow the lid on the global carbohydrate conspiracy.

Part of the experiment was not only to look at changes in weight but also to see if we were generally healthier and perhaps happier as well….there’s no point being thin if you are sick.  We wanted to measure more than just our weight and our waistlines, so to put some basic science behind the experiment,  Naomi and I decided to first get our health bio-markers accurately logged through full body DEXA scans and blood tests.  We would then get reassessed at the end of the six weeks and compare the results.  In addition to the before and after analyses, we also decided to monitor our blood ketones on a daily basis.  This involves a finger prick blood test, similar to that conducted by diabetics, to make sure we stayed in the blood ketone range for nutritional ketosis of between 0.5 and 3.0 mMol/L.

Burn and Learn's 6 week Ketosis Experiment involved blood ketone readings three times a day

Burn and Learn’s 6 week Ketosis Experiment involved blood ketone readings three times a day

We then entered our details into a keto calculator to work out our basic dietary plan for the coming 6 weeks.  The keto-calculator is really useful as it tells you not only the calories you should take for your size, gender and age but also helps you work out the proportions of each macronutrient you need to consume to hit your targets.

So, apart from realising keto is tough, what did we learn from this experiment….?

1.     Keto is a massive fail (at least for us)!

The biggest lesson of all was that keto wasn’t for us.  When we looked at the results, none of the key biomarkers showed an improvement, despite a strict and regimented following of the program.  Our bad results included:

  • Loss of Lean Muscle: 200g loss of lean muscle for me; 300 g loss for Naomi.
  • Increased Body Fat:  3% increase for me; 4.2% increase for Naomi.
  • Higher Total Cholesterol: 1 mMol/L increase for me; 2.8 mMol/L increase for Naomi.

2.     Portion control sucks

A key learning of our keto experiment was the question of portion size.  Fats have 9 calories per gram whereas protein and carbs have only 4 calories per gram.  This means if you decide to eat 75% fat in your diet you’d better get used to smaller portion sizes.  The fats quickly suck up your daily calorie allowance, leaving you wondering if that floret of broccoli is a few centimetres too big.  I don’t think I need to explain how ridiculous this is.

It’s really (really) hard to get your portions right. At the beginning – it was tough to get the carbs down low enough to stay in ketosis.  This meant that we often needed to add things to our diet that are not usually considered gourmet, such as spoonfuls of coconut butter and fish oils. Unsurprisingly, by the end – the fats were so high that we felt like we were unnecessarily torturing ourselves.

3.     Keto has side effects!

Some of the side effects we felt during and after the Keto-experiment were

  • Keto Flu.  Lethargy, fuzzy brain, headaches, nausea, sore throat and complete all over body aches. This passes within in a day or so.
  • Fibre Issues.  The lack of fibre in my diet had big consequences. If passing cement at extremely irregular intervals is your thing then by all means try ketosis. I have a newfound respect for all things fibre.
  • Carb backlash. Following keto, Naomi and I both embarked on a 6 week uncontrollable carb binge.  For two girls who have successfully avoided sugar and high GI carbs for years, this was a surprise.  We can only put it down to over correcting after 6 weeks of torture.

4.     If you are not already crazy when you start, you become crazy pretty quickly

Pricking your finger each morning and night to get your keto readings resulted not only in bruised fingers, but an addiction to chasing that perfect keto number. The readings became an obsession and went from 1 -2 fingers jabs a day to more and more jabs, and more and more readings… yes it’s getting certifiable.

We also suffered major mental torture during social events involving food – we really both felt a genuine loss and sadness for carbs.  The thought of eating bread consumed me (even though I don’t usually eat bread)…. saying no to a piece of your friend’s birthday cake, attending high tea (torture!) or saying no to the delicious home-baked food at a family do.  Did I mention it was torture?

5.     Keto isn’t all bad

There were plenty of good things about the Keto diet, Red wine probably being the best. While Keto is so restrictive that virtually all drinks with any flavour are off the menu, red wine and black coffee (due to their low carb properties) are definitely in. Another good thing, and this might be down to personal taste, but I found I could satisfy my unnatural love of roasted cauliflower, literally the most amazing thing in the world. (We will soon be posting a few of our favourite keto recipes).  Keto also helped me to start eating eggs (before Keto, I’d had a lifelong phobia of eggs, but had longed to introduce them due to their overall beneficial properties as a food source). Keto forced me to give them a genuine go, partly as they were one of the staples of the diet and partly because my available food options were so limited.  As a result, by the end of the experiment I had developed a taste for eggs for the first time in my 37 years.

For my part the bonding over keto between Naomi and me was also a key benefit. Naomi and I sent each other countless texts and links to information in an effort to stay abreast of this all-consuming dietary approach. On reflection, this may not be a good thing. Bodybuilders connect over steroids, anorexic girls connect over food avoidance, and drug addicts connect over drugs. I will say the pain of the experiment brought us much closer, and I’m pleased to report we have fully embraced our old wellness philosophies.

But perhaps the most amazing thing about keto was that Naomi fell pregnant!  At least, we like to blame keto for this. Naomi had low body fat pre-keto that was akin to an elite athlete.  By putting on 4.2% body fat she became prime breeding ground.  This is a wonderful outcome.


Since regaining control of our eating patterns, we tend to enjoy (mostly) a balanced diet of fruit, vegetables, lean protein and balanced (and cautious) amounts of full fats.  Energy has returned to normal for me, although the same cannot be said for Naomi who is expecting.

We much prefer to recommend Burn & Learn’s recommended diet as one that allows the embracing of full fats in a balanced way, while allowing the full spectrum of macro and micro-nutrients from a wonderful array of protein, fruits and vegetables.