The ketogenic diet. Is it as effective as it seems?

Carne, pescado y huevos

What is a ketogenic diet?

The ketogenic diet is characterised by being very low in carbohydrates, between 20 grams and 50 grams per day. Less than ten per cent of the energy we consume every day would come from them, when under normal conditions they represent at least 50% of our food.

"Generally, a ketogenic diet includes many meats, eggs, processed meats, sausages, cheeses, fish, nuts, butter, oils, seeds and fibrous vegetables," says Pablo Ojeda, a dietitian specializing in TCA and obesity.

On 20 January a study was published in Nature Metabolism showing the effect of a very strict ketogenic diet on a group of mice. The diet consisted of 99% fat and one per cent carbohydrates.

What was observed is that, at the beginning of this diet, the risk of diabetes and inflammation was reduced and its metabolism improved. After a week, mice showed a reduction in blood sugar levels and inflammation. However, what the researchers found was that when the body is in this mode of ingesting 99% fat and 1% carbohydrates, in addition to producing a breakdown of fat, a storage of fat also takes place. When mice continued on a high-fat, low-carb diet for more than a week, they consumed more fat than they could burn, and developed diabetes and obesity.

The food technologist and dietitian-nutritionist, Beatriz Robles, points out that studies like this, based on animals and not on humans, cannot be used to make recommendations to the population. They can serve as a starting point, but so fa, in her opinion, the quality of the evidence in this study is very low.

Side effects of a ketogenic diet

"One of the main criticisms of this diet is that many people tend to eat too much protein and low-quality fats from processed foods, with too few fruits and vegetables. Patients with kidney disease should be cautious because this diet could worsen their condition. In addition, some patients may feel a little tired at first, while others may have bad breath, nausea, vomiting, constipation, and trouble sleeping,” says Pablo Ojeda.

Robles, on the other hand, points to the lack of fibre that usually occurs if a ketogenic diet is followed. Moreover, "All compounds that have some physiological activity and come from foods such as fruits and legumes, we will not get it", he points out. An example would be antioxidants, present in fruits.

The benefits of a ketogenic diet under examination

Two of the benefits attributed to the ketogenic diet are weight loss and reduced cardiovascular risk. For Beatriz Robles there are no significant differences between adopting this diet or another one focused on the same objectives, that is, following a ketogenic diet for a year, which would be rather complicated because of its huge carbohydrate restriction causing most people to abandon it, the weight lost would be similar.

Another benefit attributed to the ketogenic diet is that it allows controlling blood glucose in type II diabetes. It could improve blood sugar control but the quality of evidence is so low that it cannot be generally recommended.

It has also been mentioned that this diet can benefit cancer patients. Again Robles points out: "There is no scientific evidence in cancer patients. There are indications that some cases might be useful, but there is no robust evidence. Controlled and randomised trials would be needed to generate better quality evidence".

In this sense, Pablo Ojeda tells us that more and more studies are being done to see if the ketogenic diet can help cancer patients. "There are certainly more and more studies along these lines. One of the first research papers published in the magazine Cell Reports suggests that restricting blood sugar could also help combat certain growths of cancerous tumours".

"Researchers at the University of Texas, Dallas, restricted blood sugar levels in mice (not humans) by feeding them a ketogenic, high-fat, moderate-protein, low-carbohydrate diet, and by giving them a diabetes medication that prevents the kidneys from reabsorbing glucose into the blood. The combination of diet and diabetes medication did not reduce lung and oesophageal cancers in mice, but did prevent them from progressing. Both the ketogenic diet and the pharmacological restriction of blood glucose inhibited the growth of squamous cell carcinoma tumours in mice with lung cancer. Both elements also showed a promise independent of each other, the key finding of this study in mice is that a single ketogenic diet, has some tumour growth inhibitor effect on squamous cell cancer. When we combined this with the medicine for diabetes and chemotherapy, it was even more effective,” Ojeda tells us.

"I don’t think we should reject the ketogenic diet outright. It is possible that over time the scientific evidence becomes more valid and that in some pathologies it can be proposed as therapy or as a therapeutic approach, but at the moment and in general of course not", says Robles.

So, should we follow a ketogenic diet or not?

The world of nutrition is by no means alien to fashion, and the ketogenic diet is, in most cases, yet another example of this. As Pablo Ojeda points out, rather than signing up for the diet of the moment, which lasts a few weeks or months, "We must try to adopt a change that is sustainable in the long term. A balanced, unprocessed diet rich in colourful fruits and vegetables, lean meats, fish, whole grains, nuts, seeds and olive oil.” In addition, the expert reminds us that yo-yo diets, in which weight is lost rapidly, are associated with higher rates of mortality.

Knowing the side effects that a ketogenic diet can have, that cannot be recommended to the general population, as well as the lack of strong scientific evidence to back it up, our advice is that if you want to follow it, put yourself in the hands of an expert first.

Conociendo los efectos secundarios que puede tener una dieta cetogénica, que no se puede recomendar a la población en general, así como la falta de una fuerte evidencia científica que la respalde, nuestro consejo es que si quieres seguirla, te pongas antes en manos de un experto.

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