Dietary Analysis – The ketogenic diet by Tania Logan, Dietitian and Diabetes Educator

Christina ReynoldsDietetics & Diabetes Education

This is the second instalment of my analysis of some of the dietary trends that are currently popular. In this article I’ll discuss what the ketogenic diet is about, analyse the scientific evidence available and give you my verdict on whether it is worthwhile or not.

The diet

While the ketogenic diet has been a very popular diet over the past few years for weight loss and diabetes management, it has actually been around since the early 1900’s.  The diet was originally prescribed to help control seizures in children with epilepsy.

The ketogenic diet aims to force the body to burn fat stores for energy instead of the usual pathway where is utilises glucose for energy.  The breakdown of fat produces ketone bodies which can be used as an alternative energy source.  This means less insulin is required to deliver energy to our body which may reduce inflammation and oxidative stress.

There are numerous versions of the ketogenic diet available today.  Most are based on a very low carbohydrate intake of 20 – 50 grams per day. This is minimal when one apple is approximately 15 grams of carbohydrate.  Ketogenic diets are high in fat but don’t contain lots of protein.  It is important not to include too much protein on a ketogenic diet as this also stimulates glucose production and inhibits ketosis. 

Ketogenic diets avoid bread, cereals, and grain based foods.  They avoid fruit, starchy vegetables like potato and sweet potato as well as legumes.  They encourage plenty of other vegetables.  They also encourage lots of high fat foods including nuts, seeds, avocado, oil, butter and cream.  They include moderate amounts of dairy products including full cream milk and cheese, as well as meat, chicken, fish and eggs.

Once you start a ketogenic diet, it can take 2 to 3 weeks to achieve ketosis.

The evidence

There is evidence that ketogenic diets can assist with seizure control for epilepsy and there are suggestions that they may be of some benefit in the management of Parkinson’s disease and Alzheimer’s disease.

While some studies show weight loss on a ketogenic diet, the evidence does not show a clinically significant weight loss at 1 year when compared with a low fat diet.  

There is evidence to suggest that a ketogenic diet does improve lipid profile and cardiovascular risk factors.  It may also improve glycaemic control in people with diabetes but can also increase the risk of hypoglycaemia.

Possible benefits

Reducing carbohydrate intake from highly refined, processed foods is very beneficial.  This includes avoiding:

  • takeaway foods including pies, pizza, burgers, chips
  • savoury snack foods like chips, corn chips and crackers
  • sweet biscuits, cakes and pastries 
  • lollies and chocolate
  • ice cream and other desserts
  • cordial, soft drink, fruit juice
  • milk drinks including milk based coffees

Reducing your intake of these foods will assist with weight reduction, improve lipid levels and cardiovascular risk, as well as improve blood glucose levels.

Possible side effects

There are a number of side effects that are common on a ketogenic diet.  These are common for the first few weeks while the body is getting used to producing ketones for energy but they can persist past this time. These side effects include:

  • Tiredness, lethargy and fatigue
  • Dizziness or light-headedness
  • Bad breath due to the ketones being produced by the body
  • Constipation due to the reduced fibre intake
  • Electrolyte imbalances
  • Leg cramps
  • Vitamin and mineral deficiencies particularly calcium, magnesium, selenium, zinc, vitamin D and phosphorus

Gut health can also be impacted on the ketogenic diet.  A very low carbohydrate diet has less fibre and resistant starch which is essential for the health of the gut microbiome.  A healthy gut is very important to our overall health and wellbeing.

There is a suggestion that a low carbohydrate diet may affect the body’s ability to utilise carbohydrate as an energy source in the longer term.  This means that when reintroduce carbohydrate after the ketogenic diet, you may be more insulin resistant in the long term.  There is also some evidence that reintroducing carbohydrate can also impact on blood vessel and cardiovascular health.

People with diabetes who are taking diabetes tablets or insulin need to be particularly aware of an increased risk of hypoglycaemia.  With a reduced need for insulin on a low carbohydrate diet, medication needs to be adjusted before starting this type of diet.  Please see your GP or Endocrinologist, Diabetes Educator or Dietitian before you reduce your carbohydrate intake.

In a nutshell

While a ketogenic diet may assist in the management of epilepsy, Parkinson’s disease and Alzheimer’s disease, unfortunately it may not be a particularly effective at assisting with long term weight management.  There may be some improvements in lipid profile and cardiovascular risk as well as glycaemic control in people with diabetes, but this may be offset by deteriorations in these markers when carbohydrate foods are reintroduced.  A healthy diet with fewer refined carbohydrates will assist with these improvements without going keto.  My recommendation is to reduce your carbohydrate intake and improve the overall quality of your diet without going on a ketogenic diet.  You can do this by:  

  • Reducing  your intake of processed foods
  • Reducing  your intake of sugar 
  • Choosing wholegrains instead of refined carbohydrates
  • Increasing your intake of vegetables
  • Including nuts and seeds
  • Including good quality plant based fats like avocado and olive oil

If you would like help with developing healthy eating or lifestyle behaviours, or if you would like practical assistance for making any of these suggested changes to improve your health, please contact me. You can find my contact details and how to book an appointment on our website at

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