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Keto diet

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 3 minutes read

The concept of a keto diet (short for ketogenic) is for fat to provide the bulk of your daily required calories – about 80 to 90%. Protein provides a small proportion, and carbohydrates provide a smaller proportion still. This can come from certain fruit, vegetables, and dairy.

The idea behind it is for your body to switch to using energy from fats rather than carbohydrates as the fuel. This lowers the sugar level in your blood and increases the production of ketones, a chemical made by your liver as it breaks down fats. Ketones give this diet its name.

Initially, the diet was developed as a medical intervention to help lower the number of seizures in some people with severe epilepsy. It's still used in some treatment programs, but it's not common and must be led by an epilepsy specialist and a nutritionist or dietician.

Diabetics need to lower their blood glucose level, so a ketogenic diet could be beneficial in those with type 2 diabetes and prediabetes. But any long-term impact and effectiveness still need to be determined. And it does bring side effects, which can have implications for your health, so it's important to speak to your doctor or specialist doctor before starting this diet, and it should be monitored by a nutritionist who will need to tailor the diet to you.

How long does it take to kick in?

It can take around four weeks for your body to adapt to using a different energy source. Side effects include stomach upset, dehydration, an imbalance of certain electrolytes (salts) in your body (sodium, potassium, and magnesium), and bad breath. It risks a phenomenon known as keto-flu, where people experience difficulty thinking, tiredness, and difficulty sleeping. Long-term side effects can be a lack of essential nutrients needed to keep your body healthy, so supplements may be needed to prevent this.

Although the keto diet has the word diet in its name and can cause some weight loss, it's not actually what we would recommend using for this alone. This is because it is very restrictive with regards to food groups, and if used long-term, you could end up lacking essential nutrients that you would normally get from a more varied and balanced diet. It has not been proven to be more effective in the long term than following a low-calorie and low-fat diet that is balanced and varied.

When should I see my doctor?

You should speak to a healthcare professional before commencing a keto diet. This could be by booking a routine visit with your doctor or seeing your nutritionist or specialist doctor.

What will my doctor do?

The doctor will initially discuss your reasons for starting a ketogenic diet and check if it is right for you by asking about current or previous medical issues and any medication you are on. They will take initial health checks such as your blood pressure, pulse, and weight, and they may offer blood tests to look at things like your current cholesterol level, blood sugar levels, and levels of certain salts in your blood. You will also need to be referred to a dietician who will oversee the nutrition plan. You will also need to be regularly monitored by your doctor and likely undergo regular blood tests.

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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