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Ketogenic Diet

The ketogenic diet is a form of dietary therapy for epilepsy.

The traditional or "classic" ketogenic diet usually involves a ratio of 3 to 4 g of fat to every 1 g of protein plus carbohydrate. This means that about 90% of the calories in the child’s diet come from fat. Some children may need a slightly different ratio. Children on the ketogenic diet have to eat mostly fatty foods, like butter and cream. They cannot eat starchy foods like bread and pasta.

Benefits of the ketogenic diet

Although it does not work for every child, the diet has been shown to reduce seizures, even in children whose seizures have failed to be controlled with medication. In some children, it may eliminate seizures altogether. The diet may be effective as soon as one week after starting; however, it can take a few months to judge whether the diet will be effective. If it is successful in controlling seizures, it may be continued for several years under the guidance and monitoring of your child's doctor.

The ketogenic diet may also have some other positive side effects, including improvements in mood, behaviour, attention, and social functioning.

The ketogenic diet is primarily used to treat epilepsy. However, there are some metabolic disorders in which the body is unable to efficiently use carbohydrates as a fuel, including glucose transporter protein deficiency and pyruvate dehydrogenase deficiency. The ketogenic diet is a preferred treatment for these conditions as well.

Limitations and side effects of the ketogenic diet

The ketogenic diet may cause some mild side effects in some children, including dehydration, constipation, vomiting, high cholesterol, and kidney stones (due to uric acid build-up in the blood). Some families notice mood changes such as hyperactivity or irritability. More severe side effects include loss of bone density, alteration in the blood electrolytes, and poor growth. Infections may also be more severe in a child treated with the ketogenic diet.

Some side effects are reversible once the child goes back to her normal diet. For example, once the diet is ended, there tends to be a growth spurt. Some side effects, such as constipation, can be treated: ask your child's doctor and dietitian. Other effects need to be closely monitored by your child's medical team.

Ask your child's doctor to explain all possible side effects, what you should watch for, and what action you should take for each one.

It is also important for your child to take specific vitamin and mineral supplements. Your child's doctor and dietitian can advise you on these.

Before deciding to try the ketogenic diet, it is important to note that:

  • The diet is very restrictive, especially for a child. The diet controls the type of food and the quantity of food. Some children may feel isolated at school because they cannot eat “normal” food.
  • The diet will not work unless it is followed carefully, and some children are unable or unwilling to follow it.
  • It can be time-consuming and tedious to prepare. This usually gets easier as families adapt to the new routine.
  • It is not a balanced healthy eating regimen for the long term.
  • It might not work for some children, no matter how closely they follow the diet.
  • It is not safe for children with certain metabolic disorders, such as fatty acid oxidation defects.
  • The diet has some potentially serious medical side effects. Children must be followed closely by a doctor during treatment with the ketogenic diet.

Starting the ketogenic diet

Before starting the ketogenic diet, your child will need a full evaluation. This will include a physical examination, with measurement of her height and weight and a number of blood and urine tests. The team will also ask for a diet history for your child, including what she eats at home, what she does and does not like to eat, how much she eats, whether you see any problems feeding her the diet, and whether your family has any cultural or religious food restrictions.

The ketogenic diet is usually started in the hospital. Your child will be admitted to hospital for a stay of 5 to 8 days. You may be asked to feed her a specific low-carbohydrate menu the day before.

In the past it was common for some children to undergo a complete fast, which could last up to 36 hours, before starting the diet. During this period, they could not eat any calorie-containing foods and could only drink water, diet drinks, or diet jello. However, recently, most doctors are starting the diet without this prolonged fasting period.

As your child begins the diet, ketones will appear in the blood and urine. These will be measured at regular intervals. Your child's blood sugar will also be measured.

The diet is gradually introduced over several days so the body can get used to the change in food. Supplements of vitamins and minerals are also given to maintain a balance. Water and fluids may be restricted or encouraged, depending on the individual child.

While in the hospital, your child will be closely monitored with urine and blood tests, and your child will be watched for any side effects such as low blood sugar, vomiting, or lethargy. Your child may feel a bit tired during this initial period as her body is getting used to the diet.

Some centres now start dietary therapy without a hospital admission. However, thorough training of caregivers is still required.

Learning to use the ketogenic diet

In the meantime, the team will train you on how to administer the diet. A dietitian will explain how to plan menus, what food to use, how to read nutrition labels, how to prepare the food, quantities, feeding times, and side effects to watch for. She will give you vitamin and mineral supplements that your child will need, and explain where to buy more. She will also help you with strategies for dealing with problems you may encounter while your child is on the diet, including illness, hunger, refusing food, dehydration, constipation, low blood sugar, and high or low ketones.

A nurse will train you on how to measure your child's blood sugar and urinary ketones and how to keep track of her body weight, fluid intake, and seizure activity.

After about 5 days in the hospital, once the diet is established, there are no complications, and you have been trained on the diet, the child is released from the hospital and you can continue the diet at home. The team will explain what to do if you have any questions.

Using the ketogenic diet at home

Sticking closely to the diet is very important to ensure your child has given it a proper try and to see if it can control your child's seizures. It will take several weeks or even months on the diet to see if it reduces your child's seizures. However, straying from the diet, for example by having a couple of extra cookies, can have an almost immediate negative effect. If you find the diet too restrictive, speak to your dietitian and doctor to discuss ways to alter it to make it easier to use. Changes to the diet could mean changes to content, quantity, or scheduling.

Children on the ketogenic diet require frequent monitoring, usually every month for the first few months and then usually every 3 to 6 months. Check-ups will include measurements of weight and height, as well as urine and blood tests.

Between appointments, you will need to keep track of your child's seizure activity, urinary ketone levels, blood sugar levels, fluid intake, and body weight.

Because your child is growing, the diet may need to be adjusted periodically to give her enough energy.

Some medications, including over-the-counter cough and cold medicines, IV fluids, and even toothpaste, have sugar (carbohydrates) in them. The dietitian will explain how to avoid using any medications with carbohydrates. Whenever you take your child to the doctor, or get a new prescription, you need to inform them that your child is on the ketogenic diet.

Discontinuing the ketogenic diet

After several years of well-controlled seizures, in consultation with your child's doctor, the diet may be tapered off. Alternatively, if it is not working or you find it too restrictive, the diet may be tapered off or your child’s doctor may suggest switching to a different diet.

The ketogenic diet should not be stopped abruptly. It is usually tapered slowly over a 3- to 6-month period, during which the levels of protein and carbohydrate are gradually increased and the level of fat is reduced. Your child's dietitian and doctor will work with you to discontinue the diet.

Elizabeth J. Donner, MD, FRCPC