By Paul Stevenson

Having been in the fitness industry for the best part of a decade I have witnessed and utilized a whole host of different dietary approaches, some seemingly more intelligent than others. Here I want to present a guide to ‘Ketogenic Diets’, an approach that has received a great deal of attention over the past few years.

What is a Ketogenic diet?

A ‘Ketogenic Diet’ is a form of very low-carbohydrate diet (VLCD) that results in the production of the ketone bodies acetoacetate, beta-hydroxybutyric acid and acetone. These ketone bodies are produced as certain tissues in the body, namely the brain, cannot use fat as fuel. Therefore, when glucose is scarce (due to low-carbohydrate intake), the liver must convert fatty-acids into ketones. Generally speaking, carbohydrate intake must be restricted below 100g per day to be considered ketogenic, though overall intakes can vary from person to person.

Ketogenic diets have been used historically in the treatment of childhood epilepsy, but have recently also been used in the treatment of respiratory failure, polycystic ovary syndrome, acne, neurological diseases and certain types of pediatric cancer (Paoli, et al, 2013).

However, more recently focus has turned to the ketogenic diet as a means to treat obesity. Ketogenic Diets really entered the mainstream in the 1970’s with “Dr Atkins Diet Revolution”, and again in the 1990’s with Dr. Mauro DiPasquale’s “Anabolic Diet”, and Dan Duchaine’s “Underground Bodyopus”.

These are some of the foods that help comprise a Ketogenic diet...

These are some of the foods that help comprise a Ketogenic diet…

How do I enter Ketosis?

First it must be understood that even under ‘normal’ dietary conditions, the liver is always producing ketones and they are always present in the bloodstream. A ketogenic diet will increase ketone production, and thus concentrations in the blood will increase. “Thus ketones should not be considered a toxic substance or a byproduct of abnormal human metabolism. Rather, ketones are a normal physiological substance that plays many important roles in the human body” (McDonald, 1998).

Ketosis represents the shift from a glucose-based metabolism, to a fat-based metabolism. Initially any carbohydrate intake below 100g per day will induce ketosis. However, as the brain adapts to using ketones for fuel, less carbohydrate must be consumed to maintain ketosis. Carbohydrate intakes of 20-50g are required for long-term ketosis (Sumithran & Proietto, 2008).

How do I know if I am in Ketosis?

Ketone concentrations in the bloodstream are the only true indictor of ketosis. However, measurement is impractical as a blood test is required. Another way of measuring ketosis is indirectly through the use of Ketostix which detect the concentration of ketone bodies in the urine. It takes approximately 48 hours to reach ‘nutritional ketosis’, but rates will vary depending on activity levels.

Will I lose muscle mass on a Ketogenic diet?

Contrary to the above, ketogenic diets are actually protein sparing. The major mechanism behind the protein sparing effect of ketogenic diets is the body’s shift to primarily using fat and ketone bodies for fuel, resulting in less protein being converted to glucose.

Do I Need to Consider Protein Intake?

As well as ensuring carbohydrate intake is kept below the requirement for the maintenance of ketosis (100g per day initially and less than 50g in the longer-term), protein intake also must be considered. For anyone involved in resistance training or sport of any kind, maintaining the general protein recommendations of 1.8g of protein per kg of bodyweight per day will be extremely important to ensure the preservation of muscle mass.

However, excessive protein intake can be problematic on a ketogenic diet, as 58% of dietary protein will appear in the bloodstream as glucose. In other words, 58g of glucose can be created from 100g of protein (Jungas et al, 1992). This means that protein intake cannot be too high. Thus the bulk of calories on a ketogenic diet come in the form of fat.

Is a Ketogenic Diet Unhealthy?

On the contrary, a great deal of studies have outlined many health benefits of ketogenic diets. Studies have shown Ketogenic diets to be extremely effective in reducing insulin resistance and type II diabetes (T2D):

“Individuals with metabolic syndrome, insulin resistance and T2D (all diseases of carbohydrate intolerance) are likely to see symptomatic as well as objective improvements in biomarkers of disease risk if they follow a well formulated very-low-carbohydrate diet” (Paoli et al, 2013)

For the brain and nervous system health, ketogenic diets can be very beneficial. Paoli et al (2014) describe benefits in the treatment of Parkinson’s and Alzheimers Disease, reduced amount of oxidative stress compared with glucose metabolism and an increased mitochondrial biogenesis pathways, which can help improve brain and neuronal metabolism.

Is a Ketogenic diet sustainable?

There is certainly no reason why someone could not maintain a ketogenic diet in the long-term such as 6 months or longer. However the very restrictive nature of the diet makes it difficult for many people to follow and make a lifestyle. The types of food available on a ketogenic diet are:


  • Meat
  • Poultry
  • Fish
  • Eggs


  • Oils
  • Eggs
  • Butter
  • Cheese
  • Nuts
  • Avocado


  • Leafy Greens
  • Asparagus
  • Broccoli
  • Brussel Sprouts
  • Cauliflower
  • Mushrooms
  • Tomatoes
  • Celery
  • Zucchini
  • Capsicum

Therefore the adoption of a ketogenic diet will mean eliminating most dairy, fruit, grains, beans, legumes, starchy vegetables (such as sweet potato) and slightly sweet vegetables (such as carrots). This can make it extremely difficult to follow in the long-term.

It should also be noted here that good food choices are very important when following a ketogenic diet to ensure that enough dietary fibre is consumed. Many fibre-containing foods are restricted on a ketogenic diet, so supplementing with fibre may also be necessary. Also, it may be very difficult to obtain all the necessary micro-nutrients, meaning vitamins and minerals, from such a restricted diet. As a result the minimal daily carbohydrate intake should consist of maximum amount of vegetables possible. The use of a supplemental multi-vitamin, providing at least the RDA for all nutrients, is advised.

Who might benefit most from a Ketogenic diet?

There are two groups of  Clean Health Fitness Institute Sydney CBD and Chatswood personal training clients whom I recommend may benefit most from ketogenic diets. The first group would be obese members of the population looking to lose body fat. People with obesity tend to have metabolic syndrome, and the benefits of ketogenic diets on improved cardiovascular health and carbohydrate tolerance are well-established.

Secondly, a well-designed ketogenic diet will produce fast fat loss results whilst maintaining satiety in dieters. Indeed, many studies have found ketogenic diets to be extremely appetite suppressing (Gibson, et al, 2014), which is vital for long-term adherence to an energy restricted diet. However, there is a great deal of inter-individual variability in hunger suppression, with some people feeling no appetite-suppression. For these individuals a different dietary approach may be more prudent.

The second group who may benefit from ketogenic diets are figure competitors/bodybuilders who are looking to drop body fat to extremely low levels whilst preserving muscle mass. This is due to the protein-sparing nature of ketogenic diets, in spite of calories being dropped extremely low. The appetite-suppressing nature of the diets will also be helpful to competitors. Depending on how much fat a competitor has to lose this phase of dieting could last anywhere from 6-16 weeks out from the competition.

Take Home Points:

  • Ketosis achieved when carbohydrates are restricted below 100g per day and the body shifts from a glucose-based metabolism to a fat-based metabolism.
  • Ketogenic diets can confer a raft of health benefits, including brain and nervous-system health, improvements in insulin sensitivity, reduced inflammation and reduced risk of T2D.
  • Restrictive nature of ketogenic diets means they can be unsustainable for some people.
  • The obese members of the population and figure competitors/bodybuilders in particular can benefit a great deal from ketogenic diets.


Sumithran, P & Proietto, J, “Ketogenic Diets for Weight Loss: A Review of Their Principles, Safety and Efficacy”, Obesity Research & Clinical Practice, 2008.

McDonald, L, “The Ketogenic Diet”, 1998.

Jungas, R, et al, “Quantitative Analysis of Amino Acid Oxidation and Related Gluconeogensis in Humans”, Physiological Reviews, 1992.

Paoli, A, et al, “Beyond Weight Loss: A Review of the Therapeutic Uses of Very-Low-carbohydrate (ketogenic) Diets”, European Journal of Clinical Nutrition, 2013.

Paoli, A, et al, “Ketogenic Diet in Neuromuscular and Neurodegenerative Diseases”, Biomedical Research International, 2014.

Gibson, A, et al, “Do Ketogenic Diets Really Suppress Appetite? A Systematic Review and Meta-Analysis”, Obesity Reviews, 2014.

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