Benefits and cautions of a ketogenic diet

High fat, ketogenic diets are being used therapeutically for a number of health conditions including Alzheimer’s, epilepsy, cancer and obesity. Low in carbohydrate and high in fat – a ketogenic diet might sound like a new idea, but in fact it was the way our ancestors predominantly ate and some would argue it is how we are designed to eat. Ketosis is where the body burns ketones – derived from fats. For most people, glucose from carbohydrates is the main energy or fuel source for the body.

Our ancestors had little access to sources of sugar – just some fruit and wild honey occasionally. In the autumn, they would have eaten large quantities of fruit, gaining fat to see them through the lean winter months. In the winter, this stored fat supplemented their meagre food intake. When the body switches to using fat as its main form of energy, ketones are created, mainly in the liver.

Using fat as the main fuel is called ketosis and our ancestors would have spent a large proportion of time in ketosis. Today, some populations in the world still consume a largely ketogenic diet. For example, the Inuit’s traditional diet is ketogenic –  including nutrient-dense foods obtained from the local environment and comprising largely wild game, marine mammals and fish.

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What is a ketogenic diet?

A ketogenic diet is high in fat, moderate in protein and very low in carbohydrate which causes the body to behave in a similar way to periods of limited food availability. The diet is composed of around 65% – 80% fat with carbohydrate and protein constituting the remainder of the intake.

Ketones explained

Between meals, as well as during fasting, starvation and strenuous exercise, when blood glucose levels fall, fatty acids are released from adipose tissue and can be used by most cells as a fuel source (except brain cells which are unable to uptake fatty acids). In the liver some fatty acids are formed into ‘ketone bodies’ – acetoacetate which is then further metabolised to beta-hydroxybutyrate and acetone. Ketone bodies can be used by tissues, including the brain, as a source of fuel.

How much fat, protein and carbohydrate to eat

In order for the body to switch to ketosis, carbohydrate intake needs to be low eg below 50 g per day of net carbs. Some people may achieve mild ketosis at a higher level of carbohydrate than this, others may need to go lower initially, for example, people who are overweight or with metabolic syndrome may need to reduce to below 20 g per day. Net carbs is the amount of carbohydrate minus the fibre.

In Europe food labels generally show net carbs, while in the US labels show total carbs. Net carbs can be calculated by subtracting fibre from total carbs. Carbohydrates should come mainly from vegetables, nuts/seeds, with small portions of fruit such as berries. At 50 g of carbs per day it is still possible to eat 7+ portions of non-starchy vegetables.

There is no restriction on the amount of healthy fats that can be eaten, however once ketosis has been achieved appetite should decrease. It is important to eat plenty of fat to stay in ketosis. So foods such as avocado, olive oil, coconut oil, MCT oil can be eaten liberally. Nuts, seeds, wild oily fish and eggs provide other sources of healthy fats.

Fat phobia may cause people to reduce carbohydrates without increasing fat in the diet, however, a low carb / low fat diet will not achieve sustainable ketosis. On the other hand, beware – eating a high fat diet without restricting carbohydrate sufficiently may lead to weight gain and other health problems.

Medium chain triglyceride (MCT) oil is often used in ketogenic diets. MCTs are a type of fat that can be rapidly and easily converted to ketone bodies in the liver. Coconut oil is a good source of medium chain triglcycerides, eg caprylic acid, but MCT oil is also available and this contains higher concentrations. It can be eaten off the spoon or added to food/smoothies. When adding MCT oil to the diet it is best to start slowly eg one teaspoon per day to avoid any unwanted gastrointestinal side effects.

Protein in foods can be converted by the body to carbohydrates so excessive protein needs to be avoided. Between 0.8 to 1.2 g of protein per kg body weight depending on the level of activity (ie higher level for those who are very active / undertaking strenuous exercise and weight training on most days of the week).

Fasting can be useful to help achieve and maintain ketosis. For example, a 16 hour overnight fast ie skipping breakfast. This would also include avoiding milk etc in drinks and caffeine which stimulates a blood sugar response.

Benefits of a ketogenic diet

The ketogenic diet, if done correctly, can be an ‘anti-inflammatory’ way of eating. When we eat carbohydrate our blood sugar increases and this creates some level of inflammation in the body. Ketogenic diets can:

  • Lower blood sugar (and thus lower inflammation) and reduce the risk of metabolic syndrome and diseases associated with it
  • Control appetite – ketosis affects ‘hunger’ hormones and allows us to feel full for longer. In contrast, eating a lot of carbohydrates can have the opposite effect
  • Help with weight loss
  • Support memory – research is showing the benefit of ketogenic diets in symptomatic relief from Alzheimer’s and ketosis may have disease-modifying activity through a number of different mechanisms. Increased mental focus can be gained from the diet as ketosis provides a steady flow of ketones to the brain which avoids large spikes in blood sugar levels. The brain’s preferred fuel source is glucose, however, in cognitive decline the brain may struggle to use glucose; this has a dual consequence – the brain is starved of the fuel it needs to function well AND glucose levels in the brain remain high which can cause damage to brain cells. Switching to using ketones as the main source of energy bypasses both these problems and is the therapeutic diet being used by Professor Bredesen in the USA to reverse cognitive decline
  • Improve physical stamina – ketogenic diets are used by some sportsmen for endurance events
  • Improve sleep, immunity, anxiety, mood and overall feeling of wellbeing
  • Epilepsy – The ketogenic diet has long been associated with helping to manage epilepsy. It was discovered to help control symptoms back in the 1920s and was mainly used to help treat children with uncontrolled epilepsy. Controlled trials have shown that the diet can control seizures and more recent results have shown adults as well as children can benefit from it. It can also reduce the need to take anti-epileptic drugs. Specialist dieticians are available to guide patients on the use of this diet.

Is it safe to go on a ketogenic diet?

Some diets which are ketogenic are not recommended, ie diets which are high fat but place little emphasis on the types of fats included (ie they allow processed and inflammatory fats) and diets which encourage protein and fat intake at the expense of vegetables.

The majority of people can safely go on a well-planned ketogenic diet, however, those with serious medical conditions should only undertake this diet under the supervision of a health professional. The diet may not be suitable for those with diabetes, thyroid and liver disease. For example, people with diabetes are at risk of developing a condition called diabetic ketoacidosis which can be fatal. [However, a low carbohydrate diet is recommended for those with diabetes and some people with diabetes may be advised to follow a ketogenic diet with appropriate monitoring and supervision].

For anyone embarking on a ketogenic diet it is recommended that blood monitoring is undertaken at the start and after 2 to 3 months to monitor and check for any adverse changes. Tests to include: Complete blood count, fasting blood sugar, HbA1c, fasting lipid panel, thyroid panel, liver function, kidney function and electrolytes.

Some people can feel unwell in the first few days of changing to this diet – referred to as Keto Flu. This can be helped by eating some salt daily and staying hydrated (urination may increase for a few days).

Increasing fat in the diet and the addition of MCT oil can lead to intestinal symptoms (including diarrhoea), so transition to this new way of eating may be best done slowly, starting with 1 teaspoon of MCT oil per day with food and increasing gradually. If symptoms occur reduce to a lower dose.

Long periods of ketosis can result in loss of muscle and increased fat. Whether this occurs, and how quickly, depends on the person, some endurance athletes use a ketogenic diet very successfully. For the rest of us it may lead to loss of muscle if carried out long-term due to the very low insulin levels. Although in general reducing insulin is one of the benefits of ketosis, one of the actions of insulin is to inhibit gluconeogenesis by the liver (gluconeogenesis is the conversion of protein to glucose); low insulin results in increased gluconeogenesis and muscle breakdown to provide the protein.

Whilst the brain can run on ketones it does require a small amount of glucose. So after a few weeks of being in ketosis, it may be preferable to eat a larger amount of carbohydrates on 1 or 2 days per week (eg a sweet potato and couple of portions of fruit).

There has also been concern raised that ketogenic diets raise cortisol and so some advise that a ketogenic diet should not be undertaken by people under a lot of stress or continued long-term. A 2012 study compared 3 diferent diets (low fat, low carb, low glycaemic index). The study showed the low carbohydrate diet produced the best effects overall but also raised cortisol levels, which can lead to insulin resistance etc. However ketogenic diets have also been shown to reverse symptoms of metabolic syndrome – so this is an area that would warrant further research.

Finally, the intake of certain micronutrients may be lower on a ketogenic diet – this can be minimised by carefully planning the diet. We would also recommend taking an all-round multivitamin / mineral daily.

 A ketogenic diet is not advised for people with certain health conditions. Therefore, we recommend only embarking on a ketogenic diet with advice and guidance from a suitably qualified health practitioner.

Key Takeaways

  • A ketogenic diet is high in fat, moderate in protein and very low in carbohydrate. Fat intake is between 65 – 80% of total energy intake.
  • Foods eaten include olive oil, butter, coconut oil, MCT oil (medium chain triglycerides), wild oily fish, avocado, nuts/seeds and non-starchy vegetables.
  • Ketones are made in the liver and can be used by tissues, including the brain, as fuel.
  • Reported benefits include reduced hunger, improved mental clarity and weight loss. The diet is being used therapeutically for a number of conditions including Alzheimer’s, cancer and epilepsy.
  • The diet may be best used short or medium term. If planned for long-term use then it may be beneficial to have one or two days per week with a higher carbohydrate intake (eg a sweet potato and couple of portions of fruit).
  • Intake of certain micronutrients may be low on a ketogenic diet, we would recommend an all-round multivitamin / mineral daily.
  • Due to the restrictions of the diet, advice of a suitably qualified health practitioner is recommended. It is not suitable for people with certain health conditions.

If you have any questions regarding the topics that have been raised, or any other health matters please do contact me (Clare) by phone or email at any time., 01684 310099

Clare Daley and the Cytoplan Editorial Team

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Ebbeling C B (2012) – Effects of dietary composition during weight loss maintenance: a controlled feeding study. JAMA, 307, 24, 2627-2634

Kemp D & Daly P (2016) – The Ketogenic Kitchen. Gill Books, Dublin

Mercola J Dr (2017) – Fat for Fuel. Hay House Inc

Moore J & Westman E C (2014) – Keto Clarity. Victory Belt


Last updated on 4th April 2019 by cytoffice


12 thoughts on “Benefits and cautions of a ketogenic diet

  1. Thank you for the article.

    The ketogenic diet can be very helpful, but it is not easy to follow this diet plan, especially at the beginning.

    Also, some other benefits of keto diet are helping with skin problems, preventing cancer, protecting the heart.

    1. Don’t gut bacteria need some resistant starch to survive? Perhaps this diet should be combined with some pre-biotics?

  2. A really well written and clear article, putting every aspect of the ketogenic eating style, however there was no detail on how to follow this diet for the beginner, such as cutting out all factory processed foods, all sugar , starch, sugary drinks , alcohol intake and what fruits to avoid.

    1. Hi Peter,

      Thanks for your comment on our blog. I intentionally didn’t include any ‘how to information’ in the blog as a ketogenic diet is quite complex and really best done under the guidance of a Nutritional Therapist who has experience of using the diet. There are a few potential pitfalls and a ketogenic diet is not suitable for everyone. There are a few books on the subject but I really do think this is best done with more guidance.

      We do have some general nutrition advice which covers the points you make in our booklet “Your Guide to Eating Well” – you can download a copy here. This would be a good place to start for anyone wanting to improve their diet – with increased vegetables, healthy fats etc.

      If you are interested in guidance in following a ketogenic diet you could have a look for a Nutritional Therapy practitioner on our website The Brain Health Programme – hopefully there will be a practitioner in your area who can help you (most practitioners also offer consultations via video conference e.g. Skype or Zoom).

      I hope this helps.

      Best wishes, Clare

  3. Now I have 84kgs weight,my body has started developing mild blood pressure and some pain in my ankles n elbow which I think is uric acid,how can I be assisted as per this ketogenic diet..

    1. Hi, it would be better for you to find a practitioner to work with in order to implement the ketogenic diet in a way that would be both gentle and effective for you. It certainly will be able to help you with the problems you have but I always feel that ketogenic diets are best undertaken under knowledgeable supervision.

  4. hi, I am taking statins and blood pressure medication/ would the keto diet be possible while taking these medications?

  5. Hi, I have gallbladder stone size in 13mm and also I have amblical erniya is the right way to do keto diet ?? pls help

    1. I think it would be best for us to have a good look at your diet and get a little more information about your current health concerns. Please complete our online health questionnaire and one of our nutritional therapist team will come back to you.

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