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If you follow me on Instagram (@holdaway_dietitian) you will know that I recently undertook an experiment following a strict ketogenic diet for a fortnight. I did this while also tracking my blood glucose levels with a FreeStyle Libre (a ‘flash glucose monitoring system’), as well as assessing blood ketone levels via separate finger-prick tests. This blog will focus more on the ketogenic diet, and in due course I will write a separate blog on my experience using the FreeStyle Libre.

I kept track of my blood ketone levels with regular finger-prick tests.

With this experiment I wanted to do it as thoroughly as I could over the course of just over two weeks. I thought the best way to write this post was to answer the most common questions people asked me along the way, and those that I often get asked as a dietitian. If you have any other questions, please feel free to ask!

So, what is the ketogenic (‘keto’) diet? Basically, it is an extremely restrictive diet whereby you consume less than 20g of total carbs per day, or about 5% of your total energy intake. To put this in perspective, one slice of your average bread is about 15g of carbs. However, the level of carbs required to get in ketosis varies between individuals. For example, a more active person might get away with eating more carbs (~50g/day) but still manage to stay in ketosis. On the keto diet it is essential that most of your energy comes from fats (70-80%) and the remainder is from protein. It is important that you don’t eat too much protein either, and I will explain why later. Obviously, for someone as active as me whereby carbs are key for good performance, I knew this experiment was going to be tough both mentally and physically. I managed to stick to between 15 – 25g of total carbs every day.

What is nutritional ketosis? Ketosis is a normal metabolic state. It can be undertaken by the body for months, or even years. Ketosis is a metabolic state whereby your body is burning fat as its primary fuel source instead of its preferred fuel of glucose. This is achieved through accelerated production of ketones by carb restriction.

Carbohydrate intake and ketone levels

How do people get into nutritional ketosis? I got into ketosis quite rapidly with a tactical plan. I stopped eating around 7pm Saturday night and then ran fasted for an hour 9am Sunday to drain my muscle and liver glycogen stores (our reserve of glucose for the body to use). I then broke the fast around 11am with my first keto meal of the experiment (16 hours fasting + 1 hour of exercise included + no more carbs). By the following day I was making good levels of ketones. Without exercise it would typically take 2-3 days to start making good levels of ketones. However, fasting and exercise can accelerate ketone production.

So can I just eat loads of protein? No. As mentioned above protein also needs to be moderated. This is because excess protein can stimulate a similar insulin response to carbohydrates (but much more modest). Excess protein can also be converted into glucose. Everyone has their own protein needs depending on their body size, activity levels, and age. Protein intake will typically range between 0.8 – 1.5 g/kg/day for most people on the keto diet.

What are ketones? Ketones are energy containing substances derived from body fat that has either been stored (as body fat) or eaten (in recent food intake and is being transported in the bloodstream). Being in ketosis is a natural state for the body and is the automatic mechanism that kicks in when our short-term supply of stored glucose (known as glycogen - stored in our liver and muscles) runs out. Babies and children get into ketosis quite rapidly compared to adults.

What foods did I miss the most while on keto? Fresh fruit (I was craving green pears!), eggs on nice whole grain toast (the real kind), and nice milky coffees…because nut juice (aka almond milk) just doesn’t cut the mustard for me personally!

Did keto change my relationship with food? Yes, a bit, temporarily. I think if I continued to do keto for months on end I would easily become obsessed. Being an A-type personality at heart, trying to be ‘perfect’ with a highly restrictive diet is a recipe for disaster. Even as a dietitian with my focus being on balance and enjoyment with all food, obviously excluding dietary experiments like this, it was triggering in terms of negative food thoughts. This is a classic example of just how toxic diets are to our mental wellbeing!

Is the keto diet a calorie restricted diet? It shouldn’t be. The keto diet when done correctly is a satisfying diet so you will often find you will feel satisfied with less. You shouldn’t often feel hungry with a well formulated keto diet. Although calorie counting is not required, tracking of macronutrients is vital if you are wanting to stay on track and also testing semi-frequently with finger prick blood ketone strips.

How do I know I’m in ketosis? The most accurate way is with a finger prick test with a meter that measures blood ketones, as shown in the top picture. It is always interesting having patients come in and say they are doing the keto diet but after doing a bit of a food recall they are still eating 100 - 150g of carbs per day and then a simple finger-prick test confirms nil ketones. However, often these patients have improved their food intake by cutting out high-sugar and highly processed foods which is good for anyone's health!

How was my exercise performance? My exercise performance suffered in the short time frame (2 weeks) BUT perceived effort of exertion improved by week two. In the first week ALL exercise felt like death, but my runs in the second week felt slightly better. A small amount of this was probably psychological too. For example, even before starting one of my higher intensity interval sessions I knew it was going to hurt (more than usual) – and it sure did!! In fact, one of the workouts I couldn’t complete the last couple of reps, my whole body felt like it was seizing up and just felt so weak and jelly-like! Recent research shows it takes 3-4 weeks for your body to become ‘fat-adapted’ to burning fat for fuel rather than glucose. Most research supports the concept of carbohydrates always being superior for high intensity exercise, but endurance athletes may benefit from a low-carb, high-fat intake only ONCE they are fat-adapted. The issue is, many studies undertaken that compare carbohydrate fuelled exercise to fat-fuelled exercise often include athletes that are not yet ‘fat-adapted’, i.e. short-term results. Research is always evolving, so watch this space.

What about meals? Although time consuming, it was enjoyable making everything from scratch and trying different recipes, e.g. homemade keto bread, homemade burger buns, keto pizza bases, and seeded crackers, they were all delicious! Some of these recipes have now become favourites in our household as many keto recipes are also naturally gluten free which is awesome. Obviously being a nutrition-focussed individual, I was always looking for ways to get as much nourishment as I could while still meeting my macronutrient targets. However, I can see people who are not as clued up in nutrition may just revert to food options that are not as nutrient-dense and end up lacking in dietary fibre as well as vital minerals, electrolytes and vitamins. A keto diet doesn’t make someone healthy, in fact, people undertaking any type of highly-restrictive diet are at greater risk of inadequate nutrition.

Delicious keto pizza

How do you know how much carbohydrate you’re eating? It took up a lot of time and effort weighing every single gram of ingredients ...and I mean down to every gram. I got a bit sick of having to track my intake so meticulously all the time, scales, app, scales, app, record, look up, google, weigh, triple checking food labels etc. As nice as the meals were, the preparation and measuring that went on before I could eat became a bore and added unnecessary stress. When you’re tired and hungry having to weigh and track everything so precisely it is just a nuisance. Although I do use nutrition tracking apps off/on for personal interest and with experiments, it should be noted there is always going to be some error and variability in what you are EXACTLY eating. It doesn’t matter how pedantic you are, even in some of the best nutrition studies it is nearly impossible to know exactly how much an individual is eating and burning. It’s always a ‘pretty good estimate.’

Keto bread was a great addition to busy work day lunches.

What about side effects? One of my favourite side effects while undertaking the keto diet was how satisfied I was between meals and how much my appetite was suppressed. Some days I struggled to meet my energy requirements as I continued to eat to my bodies cues (I am a strong believer of intuitive eating and listening to your body) of which sometimes this just wasn’t enough. This is likely where people see weight changes undertaking the keto diet (i.e. energy deficit) rather than the actual spread of macronutrients. Calorie deficit = weight loss. The first and second day of the keto diet were the hardest, mainly due to extreme fatigue and feeling irritable, besides from that I didn’t experience too many other negative side effects, with the exclusion of exercise. I noticed a big increase in my thirst, and on average my fluid intake was about double that of my normal intake. I also experienced unpleasant sensations of ‘seizing up’ while exercising, like cramp, but it felt like I couldn’t move my neck and my arms were stiff – weird, and very unpleasant! I found exercise psychologically and physically harder too, like a lot. As mentioned above, exercise was not very pleasant with no carbs.

Keto wraps

What about weight loss? As to be expected I had rapid weight loss due to the depletion of glycogen stores and fluid loss in the first few days. My weight change overall was -2.5kg during the experiment and I gained +1.5kg back as soon as my usual food intake resumed. Since the experiment I have remained at a slightly lower weight.

What about eating out? Social situations were tricky – even just wanting to have some nice fresh fruit off a platter – nope … Or one bite of cake to celebrate someone’s birthday – get real! Food is such a big part of social occasions, and as humans it is a way we come together and celebrate. No one likes being the odd one out because they can’t eat anything!

What about my cholesterol levels? I was surprised by these. I had baseline levels done in July, of which everything else remained consistent until I undertook keto. On the last day of my keto experiment I got a blood test to check my lipid profile. My total cholesterol and LDL had both increased by 1.0mmol/L EACH. I was surprised by how rapidly these changes had occurred, and not in the right direction! My overall cholesterol levels were still ok, but LDL is not one you want to be increasing. I’m not sure I would want to find out how my levels would trend if I were to continue keto longer term!

Can anyone do keto? No. Please go and see your doctor before putting yourself on this diet, even if you think you are otherwise healthy as it is still a good idea to keep track of regular blood work. This diet is not for the faint hearted and can be incredibly dangerous for people with some medical conditions (e.g. type 1 diabetes) or people on certain medications.

Overall, I found the experience a great learning curve. I feel much more confident when I have patients quizzing me about the diet, and I also have a greater understanding of the research out there. Whilst undertaking the diet I spent quite a bit of time each day reading and researching, especially around low carbohydrate diets and athletic performance. A lot of the research is still quite mixed and conflicting, but the takeaway surrounding sports appears to be that high-intensity exercise is always better with carbs in the system, but endurance athletes may be able to 'fat-adapt' over time and perform well on lower carb, higher fat diets. I also think I am more open to the idea of lower-carb (not keto, just lower carb) eating in some population groups (e.g. insulin resistant individuals) or athletes ‘training low’ before carb loading to get a bigger impact come race day.


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