What is the ketogenic diet?

A ketogenic (or 'keto') diet is a low-carbohydrate, high-fat diet. While it has benefits as a medical treatment for certain groups of people, there is little evidence to support it as a long-term weight loss diet.

People on a ketogenic diet eat:

• a very small amount of carbohydrates
• some protein
• a high amount of fat

When you eat, your body mainly breaks down carbohydrates into glucose, but it can also break down protein from food or muscle if needed. This glucose is then used for energy to help your body function.

If you eat more fat than carbohydrate or protein, then your body will break down the fat into 'ketone bodies' (or 'ketones') as energy. This process is called ketosis.

If too many ketones build up in your blood, it can lead to ketoacidosis. This is a life-threatening state where your blood becomes too acidic.

What do you eat on the ketogenic diet?

On a ketogenic diet, you usually eat only 20 to 50 grams (g) of carbohydrate per day. As an example, 50g of carbohydrate is equal to about 2 slices of bread and a banana. Carbohydrate makes up about 10% of your daily intake on a ketogenic diet. This means your body breaks down fat for energy and stays in a state of ketosis.

What is a carbohydrate?

Carbohydrates, or 'carbs', are important nutrients. They are an excellent source of energy for the body and especially the brain. You need carbohydrates to avoid ketoacidosis — this is when ketone levels in your blood become dangerously high.

As well as energy, most foods that contain carbohydrates also give your body vitamins, minerals and fibre for good bowel health.

Read more about carbohydrates.

What is a fat?

Fats are an essential part of your diet. They are a source of energy and help you absorb vitamins. There are different types of fats — some are healthier than others.

People on a ketogenic diet eat large quantities of fats.

Read more about the different types of dietary fats.

What is a protein?

Your body needs protein to function properly. Protein can come from animal and plant sources. People on a ketogenic diet should eat enough protein for their body weight.

Read more about protein.

What should I expect on a ketogenic diet?

When you first start a ketogenic diet, you may experience rapid weight loss in the first few weeks. This is due to water loss because you are not eating as many carbohydrates.

The main foods you will eat on a ketogenic diet include:

• meat and fish
• eggs
• cheese
• oils
• cream
• avocado
• nuts

You may have some low-carbohydrate vegetables, such as lettuce and cucumbers. On a typical ketogenic diet, you will have only small amounts of rice, pasta, fruit, grains, bread, beans and starchy vegetables such as peas and potatoes.

It can be hard for you to get all your daily recommended nutrients while following the ketogenic diet.

Talk to your doctor or an accredited practising dietitian before you start a ketogenic diet. They can make sure that it's safe for you and that you get the right amounts and types of fats, fibre and vitamins and minerals.

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What are the effects of a ketogenic diet?

A ketogenic diet usually leads to short-term weight loss. This may be because the diet is high in fat which keeps you feeling full for longer.

There are some possible short-term negative effects of a keto diet, including:

• gastro intestinal (tummy) side effects
• headache
• nausea
• bad breath
• dehydration

There is an effect known as the 'keto flu', which can happen when you first begin a ketogenic diet. You may feel:

• dizzy
• tired
• constipated
• difficulty exercising

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The ketogenic diet as a medical treatment

There is evidence that the ketogenic diet can help manage some medical conditions, including neurological disorders, obesity and metabolic disorders. Be sure to talk to your health professional before starting the keto diet as a treatment.

Epilepsy

The ketogenic diet can be helpful if your child has epilepsy and continues to have seizures while on antiepileptic medicines. Your child should only start a ketogenic diet if their neurologist recommends it, and with the support of a specialised dietitian. Your child will also need supplements to make sure they get all the vitamins and minerals their body needs.

Diabetes

If you have type 2 diabetes, a ketogenic diet may improve blood sugar management in the short term. However, the long-term effects are not known, and eating a high-fat diet can raise your cholesterol levels.

Other conditions

There is limited evidence that the ketogenic diet can treat or cure cancer. Speak to your doctor if you are thinking about a ketogenic diet for health reasons, as there are health risks, and the diet is not right for everyone.

The ketogenic diet for weight loss

The ketogenic diet is often promoted for weight loss in people with type 2 diabetes. It can usually help in the first few months but the weight loss often doesn't last.

In people without diabetes, there may be short-term benefits but more research is needed to understand the long-term effects.

The ketogenic diet can be hard to maintain because it limits what foods you can eat. This means many people drop out of the diet. This can also contribute to unhealthy, 'yo-yo' dieting behaviour. The key to maintaining a healthy weight in the long-term is a healthy eating pattern that you can follow over time.

Risks of the ketogenic diet

Low-carbohydrate diets such as the ketogenic diet can affect children's growth and should be avoided. Eating a ketogenic diet can also affect your nutrition — you may not be getting the nutrients that you need each day.

If you take insulin or certain medicines for your diabetes (especially type 1 diabetes), you may be at increased risk of having low blood sugar (hypoglycaemia) while following the ketogenic diet. There is a risk of diabetic ketoacidosis if you take certain medicines — particularly SGLT-2 inhibitors — and follow the ketogenic diet.

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It is also not recommended to follow the ketogenic diet if you:

• are pregnant or breastfeeding
• are at risk of an eating disorder
• have type 1 diabetes
• have kidney disease

What are ketone supplements??

Ketone supplements are supplements that can increase the level of ketones in your body without the need for low-carbohydrate diets. Speak to your doctor before taking ketone supplements.

When should I speak to my doctor?

Be sure to speak to your doctor before you start the ketogenic diet to make sure it is the right choice for you. They may refer you to a dietitian to help you get enough of the right nutrients in your diet.

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Resources and support

• Find an accredited practising dietitian from the Dietitians Association of Australia, or call 1800 812 942.
• Dietitians Australia has an example low carbohydrate menu to give you an idea of what foods you would be eating on a ketogenic diet.
• If you or your child is diagnosed with epilepsy, and want to check if a ketogenic diet is a good option:
  • Visit Epilepsy Action Australia or call 1300 37 45 37.
  • Visit Epilepsy Australia or call 1300 852 853.
• The Royal Children's Hospital Melbourne also has information on ketogenic diet therapy for epilepsy in children.
• You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.