Keto diet: Do the benefits outweigh the risks?

The Vitl Nutrition Team / 3 Jun 2021

Our in-house nutritionist breaks down the keto diet, weighing up the benefits and the risks.


What is the keto diet?

It is a high fat, low-carbohydrate diet with moderate amounts of protein, which mimics starvation and forces the body into ‘ketosis’. This is a metabolic process whereby the body starts burning fat as its main source of fuel instead of glucose (a carbohydrate which is readily found in our diet; wholegrains, pasta, rice, bread, legumes, fruits and vegetables). Ketosis produces ketones, which are used by the liver to fuel the body’s cells (including the brain) instead of using the most readily available source, glucose. When following the diet, one way to know whether you are indeed burning fat is to measure the quantity of ketones in your urine. It can take a few days to reach the state of ketosis. 

The ketogenic diet is a recognised, non-invasive treatment for intractable epilepsy. This diet is not for everyone, however. It has been really hyped up in the media, but it is a therapeutic diet - it was originally developed as a last resort treatment for patients with epilepsy and is still used for that purpose.  

What are the benefits of the keto diet?

Keto is being seen as a beneficial diet to help you lose weight, especially for those who can more easily adapt to a very low-carb diet, and keep their protein and fat intake high. For type 2 diabetic patients it can be beneficial as it is a way to control blood sugar levels. By reducing the amount of carbohydrate in the diet (20- 50g/day) the blood sugar levels will stay relatively steady and the body will not produce as much insulin (which is the hormone released to take glucose out of the blood and store it in our cells). Still, following this diet must be done under careful supervision of a medical professional for those with a chronic lifestyle disease. 

Another benefit this diet can have is on weight loss. Those who are obese or overweight can benefit from following a keto diet as the body will use fat stores as its main source of energy. It is a diet that is easier to sustain than others as, although you are cutting out an entire food category, there are many alternative products that can be eaten instead. That being said, once a normal diet is resumed, weight will likely return.

What are the risks?

A common drawback from following the keto diet is the side effect known as ‘keto flu’. This can happen usually in the first week or 2 of following the diet and the main symptoms are fatigue, irritability, tiredness, sugar cravings, nausea, headaches and poor concentration which can last for between 3-5 days (or longer, depending on your genetics). The reason behind these symptoms is that the body needs time to adjust to the reduced amount of insulin in the body. It takes time for your brain and other organs to adapt to using a different source of energy. 

You may also notice you experience constipation due to the change in the composition of your diet. By removing all carbohydrates, you are reducing your fibre intake drastically which may impact your gut microbiome and lead to digestive discomfort. 

This diet may be useful for some demographics, however, it is not suitable to be followed long term, due to the deprivation of nutrients typically found in carbohydrates. The main concern is around B vitamins typically found in wholegrain products (wholemeal bread, pasta, legumes) as well as the rich array of vitamins and phytonutrients found in fruit and starchy vegetables. This can put you at risk of micronutrient deficiencies.  

Another risk of the keto diet is the high intake of saturated fats. Increased intake of this type of fats found in butter, meat fat and processed products has been linked to a risk of developing hyperlipidaemia, which, left untreated, can lead to severe metabolic and cardiovascular conditions. It is important to make sure to eat unsaturated (good fats), found in e.g. olive oil, nuts and avocado, to make sure your keto diet’s constituents are cardioprotective. 

Last, but not least, being a quite new diet, the long term effects of ketosis on our liver are still to be established. It is important to always remember that ketosis is a mechanism activated by our body under the lack of glucose (the main and initial source of energy of our brain, muscle and tissues). 

Although the ketogenic diet might yield weight loss and provide benefits for glucose levels, it has potentially dangerous side effects. Especially in patients with type 2 diabetes, it is necessary to balance the potential increase in cardiovascular risk because of the unfavorable lipid profile observed with keto diet with the benefits deriving from weight loss and improvement of glycemic control.