The Keto Diet Explained

What is the Keto Diet, and should I try it? 

The Keto Diet and Weight Loss Explained

The Ketogenic (or keto for short) Diet has become a popular topic of conversation among the fitness community over the last few years. Recently it hit the headlines again with the 0/5/100 challenge put forward by a top athlete in order to apparently prove that carbohydrates are not important. It has been labelled as an effective method for weight loss and has received criticism for being “just another fad diet”. Since the diet was brought to my awareness via influencers on Instagram promoting the life changing benefits of the Keto Diet a couple of years back, the diet has fascinated me. Despite its miracle effects on weight loss appearing everywhere on my social media feeds, I wondered if it really was the most effective dietary weight loss method or if it was just another hollow and harmful promise.

So, what actually is the keto diet and where did it come from? 

The Ketogenic Diet has been around for a long time, but its use was not designed for the fitness community or primarily for weight loss at all. In 1921, the Ketogenic Diet was first proposed as a medical intervention for pharmacoresistant (drug treatment resistant) epilepsy[1]. Over the years and after a lot of research, the diet has demonstrated an effective treatment for pharmacoresistant epilepsy in children under the supervision of medical professionals and trained nutritionists[2] [3]. It has also been found to be effective for adults with epilepsy and a couple of other medical conditions[4].

The traditional ketogenic diet is defined by its low carbohydrate high fat intake. Typically, this means less than 50g of carbohydrates per day where the recommended average for adults is between 225-325g per day. The emphasis of the diet is placed on the consumption of fat, with fat making up between 75-80% of the macronutrients* consumed (measured in grams)[4].

*the macronutrients are carbohydrates, proteins and fats

Well, what does this mean?

The primary source of energy for our bodies is supplied by carbohydrates. Most carbohydrates that we consume are broken down into glucose, which is the fuel our bodies need to work effectively and efficiently. When we don’t use it immediately it is stored in the muscles and liver as glycogen. Glucose is required for the functioning of various organs including the brain, the heart and the kidneys. The brain is particularly fussy when it comes to glucose due to its high energy requirements and even when resting, approximately 60% of glucose found in the blood is used by the brain[5].

When the body is starved of its primary source of fuel from carbohydrates, the body begins to break down fat in the liver to produce ketones in a process called ketogenesis. These ketones are then used, instead of glucose, for energy by the body and brain[6].

Keto and Weight Loss

There is a lot of evidence currently to suggest that a keto diet aids in and is effective for obesity, diabetes and other metabolic and insulin resistant conditions [5][7].

How and why the keto diet works for obesity is still subject to debate. Some believe it could work through changes to the hormones that regulate appetite, or through the direct appetite suppressant effect of the ketones themselves. Weight loss could also occur through the higher energy demands of breaking down protein to use as energy (gluconeogenesis)[8]. Immediate weight loss may also be due to the breaking down of the glycogen stores and the disposal of the water stored with the glycogen. Despite various different theories, there is no clear, primary mechanism that is understood to drive weight loss when on a keto diet.

I would like to make a note here that of the recent studies I have looked at so far, the results must be taken with caution. Many have very small sample sizes (the amount of people included in the studies) meaning that making conclusions and generalisations about the effects of the diet are very limited. A couple of the studies that have found positive results for the keto diet on weight loss have also been funded by weight-loss companies that promote the ketogenic diet despite the authors stating no conflicts of interest[9] [10].

I think what is also important to note here is that research is often conducted with medical professionals and constant monitoring of the participants health and safety. Many of the reviews and studies conclude that while it seems to be effective for rapid weight loss, the diet should be implemented with caution as well as monitored by medical and/or nutritional professionals [11]. This is not a diet to take lightly.

The Side Effects and Difficulties of the Keto Diet

When choosing foods to eat, it may not be as simple as just choosing foods higher in fat and picking out those that contain carbohydrates.

There are various types of fats, some of which are more beneficial for our bodies than others. While it is important to recognise that no foods are inherently “bad” or “good”, it is well established that there are negative health impacts of consuming a lot of foods high in saturated fats. On a keto diet, there is a concern that people will eat more saturated fats as well as unsaturated fats. Saturated fats have been associated with higher risks of cardiovascular problems[12] and liver disease[13] and research suggests that eating good quality polyunsaturated fats or carbohydrates may help to avoid or reverse the negative health effects[9] [14] [15] .

The long-term effects of the keto diet are rarely studied. Research tends to study the diet for no longer than several months. It is not clear whether this dietary approach can be sustainable for longer periods of time. Many studies have used keto diets and then transferred people or patients on to other more sustainable diets such as a Mediterranean type diet – reintroducing carbohydrates.

There has been a small amount of evidence in children with epilepsy however showing that undertaking the diet for the long-term can affect bone health and bone density[16] [17].  While this result has only been found in children who undertake the diet for a long period of time, it is also good to remember that there haven’t been many longitudinal studies in obese or diabetic adult populations.

There may also be mental health impacts of the diet. The short term and quick weight loss that is often found at the beginning of the diet may lead to obsessiveness and unhealthy attitudes around weight loss. While I have no evidence to support that the keto diet specifically may lead to problematic food relationships (because there is no research about it), there is evidence that dieting in general can lead to or is associated with difficulties with self-esteem, negative and self-blaming attitudes, as well as disordered eating[18] [19] [20].

The keto diet is also just difficult to stick to. The keto diet is incredibly restrictive in terms of what you can and can’t eat. Lots of vegetables and fruits are cut out as well as bread, pastas, rice, dairy, nuts, condiments and sauces, beans and legumes etc. Sticking to this diet can be difficult, expensive and time consuming.


While the evidence does suggest that the keto diet is beneficial for obesity, this does not mean that those of you reading this and looking for a magic weight loss solution should jump on the keto diet train. This is a difficult diet to stick to and the food needs to be carefully planned out to make sure you are receiving all of the nutrients your body needs. You should be monitored on this diet by a medical professional, nutritionist or dietitian. There are side effects to the diet and potentially more side effects that are not yet known about. There is no denying that when carefully administered, the diet can work for specific groups of people, but this should not be considered an everyday diet for the general population.

Disclaimer – I am not a medical professional, and this is not a systematic review of the literature. I have not gone through the entire evidence base for the keto diet however I have tried to take a balanced approach and look at a wide variety of evidence.

[1] Radhika Dhamija, Susan Eckert, and Elaine Wirrell, ‘Ketogenic Diet’, The Canadian Journal of Neurological Sciences. Le Journal Canadien Des Sciences Neurologiques, 40.2 (2013), 158–67 <;.

[2] Neena Baby and others, ‘A Pragmatic Study on Efficacy, Tolerability and Long Term Acceptance of Ketogenic Diet Therapy in 74 South Indian Children with Pharmacoresistant Epilepsy’, Seizure, 58 (2018), 41–46 <;.

[3] Detlev Boison, ‘New Insights into the Mechanisms of the Ketogenic Diet’, Current Opinion in Neurology, 30.2 (2017), 187–92 <;.

[4] Dhamija, Eckert, and Wirrell, ‘Ketogenic Diet’, Canadien Journal of Neurological Sciences, 40.2 (2013), 158-167 <;.

[5] Bob Murray and Christine Rosenbloom, ‘Fundamentals of Glycogen Metabolism for Coaches and Athletes’, Nutrition Reviews, 76.4 (2018), 243–59 <;.

[6] Kymberly A. Wroble and others, ‘Low-Carbohydrate, Ketogenic Diet Impairs Anaerobic Exercise Performance in Exercise-Trained Women and Men: A Randomized-Sequence Crossover Trial’, The Journal of Sports Medicine and Physical Fitness, 59.4 (2019), 600–607 <;.

[7] Ana I. Castro and others, ‘Effect of A Very Low-Calorie Ketogenic Diet on Food and Alcohol Cravings, Physical and Sexual Activity, Sleep Disturbances, and Quality of Life in Obese Patients’, Nutrients, 10.10 (2018) <;.

[8] Antonio Paoli, ‘Ketogenic Diet for Obesity: Friend or Foe?’, International Journal of Environmental Research and Public Health, 11.2 (2014), 2092–2107 <;.

[9] A. Goday and others, ‘Short-Term Safety, Tolerability and Efficacy of a Very Low-Calorie-Ketogenic Diet Interventional Weight Loss Program versus Hypocaloric Diet in Patients with Type 2 Diabetes Mellitus’, Nutrition & Diabetes, 6.9 (2016), e230 <;.

[10] Ana Castro and others, ‘Effect of a Very Low-Calorie Ketogenic Diet on Food and Alcohol Cravings, Physical and Sexual Activity, Sleep Disturbances, and Quality of Life in Obese Patients’, Nutrients, 10.10, (2018), <;.

[11] Sanjay Kalra and others, ‘Ketogenic Diet: Situational Analysis of Current Nutrition Guidelines’, JPMA. The Journal of the Pakistan Medical Association, 68.12 (2018), 1836–39.

[12] Lee Hooper and others, ‘Reduction in Saturated Fat Intake for Cardiovascular Disease’, The Cochrane Database of Systematic Reviews, 5 (2020), CD011737 <;.

[13] Panu K. Luukkonen and others, ‘Saturated Fat Is More Metabolically Harmful for the Human Liver Than Unsaturated Fat or Simple Sugars’, Diabetes Care, 41.8 (2018), 1732–39 <;.

[14] Antonio Paoli and others, ‘Ketogenic Diet and Microbiota: Friends or Enemies?’, Genes, 10.7 (2019) <;.

[15] Fredrik Rosqvist and others, ‘Overfeeding Polyunsaturated and Saturated Fat Causes Distinct Effects on Liver and Visceral Fat Accumulation in Humans’, Diabetes, 63.7 (2014), 2356–68 <;.

[16] AG Christina Bergqvist and others, ‘Progressive Bone Mineral Content Loss in Children with Intractable Epilepsy Treated with the Ketogenic Diet’, The American Journal of Clinical Nutrition, 88.6 (2008), 1678–84 <;.

[17] Peter J. Simm and others, ‘The Effect of the Ketogenic Diet on the Developing Skeleton’, Epilepsy Research, 136 (2017), 62–66 <;.

[18] Simone A. French and Robert W. Jeffery, ‘Consequences of Dieting to Lose Weight: Effects on Physical and Mental Health.’, Health Psychology, 13.3 (19941001), 195 <;.

[19] E. C. Lloyd and others, ‘How Extreme Dieting Becomes Compulsive: A Novel Hypothesis for the Role of Anxiety in the Development and Maintenance of Anorexia Nervosa’, Medical Hypotheses, 108 (2017), 144–50 <;.

[20] G. Terence Wilson, ‘Relation of Dieting and Voluntary Weight Loss to Psychological Functioning and Binge Eating’, Annals of Internal Medicine, 119.7_Part_2 (1993), 727 <;.


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