Complete guide to the Keto Diet: everything you need to know

Published: 6 May, 2024 | 11'

The ketogenic diet, also known as the keto diet (short for its English name ketogenic), is one of the trending dietary patterns, especially among those who lead an active lifestyle and want to lose weight. This type of diet generates controversy due to its restrictions on certain food groups.

We will explain what the ketogenic diet consists of and its impact on our body, with the guidance of Dr. Yaiza Acosta, a nutritionist and sports doctor.

What is keto diet?

The ketogenic diet, or keto diet, is a type of eating plan based on following a low level of carbohydrates and replacing them with high-fat foods. Typically, less than 50 grams of carbohydrates are consumed per day.

"This restriction of carbohydrates exposes the body to a state called ketosis, where it converts fat into energy instead of obtaining it from carbohydrates as usual," explains Dr. Acosta.

What is nutritional ketosis?

Our energy metabolism primarily relies on glucose from carbohydrates in the diet. However, in cases of fasting or a very low intake of carbohydrates, the availability of glucose as an energy source decreases. In these situations, alternative metabolic pathways, such as the production of "ketone bodies", are activated, resulting in a state called ketosis.

Ketosis and its function in the body

Ketone bodies or ketones are the result of the breakdown of fats and, as mentioned earlier, they are used as an alternative, adaptive, and temporary energy source for metabolism, especially for organs that normally depend on glucose. Typically, the body enters ketosis within 2-4 days of restricting carbohydrate intake.

Due to the decrease in blood glucose levels, the stimulus for insulin secretion also decreases, resulting in a significant reduction in fat and glucose storage.

Ketosis is maintained as long as our body is deprived of carbohydrates, and it is generally considered safe for two reasons:

• Firstly, because ketone bodies are produced in small concentrations without altering the blood pH.
• Secondly, and most importantly, if it is well controlled by a healthcare professional either through a therapeutic diet or weight reduction.

Benefits of the keto diet

The keto diet has been used as a special type of therapeutic nutrition in epilepsy and metabolic and neurological disorders, with good results.

Due to its low carbohydrate content, this type of diet is often associated with those who want to lose weight. Additionally, it also converts fat into ketones in the liver, which can provide energy to the brain as long as the concentrations reached do not interfere with other metabolic processes in our body. For these reasons, it is believed to have beneficial effects on cognitive and cardiovascular health.

Weight loss benefits

Recent research has shown that the keto diet can contribute to weight loss, especially through its appetite and triglyceride-reducing effects. With a low or very low intake of carbohydrates, which are the body's usual fuel for energy metabolism, it then turns to glucose and glycogen sources. Once these are depleted, the metabolism "turns to" the fat stores to obtain the required energy. As a result, there is significant weight loss in a short period due to the mobilization of fat reserves.

Furthermore, "it also secondarily induces a decrease in appetite," continues Yaiza, "this lack of appetite is explained by the fact that when in ketosis, the body understands that it already has enough energy stored in fat and does not need more food to generate the necessary energy. This is why there is a feeling of no longer being hungry, as proteins and healthy fats, albeit to a lesser extent, satisfy more than carbohydrates, and because this state of ketosis influences the appetite-regulating hormones."

Impact of the keto diet on cardiovascular health

The positive effects of the keto diet on the cardiovascular system still require further research, but preliminary results are encouraging.

Recent studies have shown significant benefits in reducing total cholesterol levels, increasing HDL (good cholesterol) and reducing triglycerides in the blood, as well as presenting a lower atherogenic index (arterial obstruction) due to the reduction in blood insulin levels, which leads to inhibition of cholesterol production.

The keto diet and its impact on glycemic control

"All foods have a direct effect on blood glucose levels," says the doctor, "specifically, carbohydrates increase these levels more quickly and to a greater extent than other nutrients." Knowing which foods contain carbohydrates and their quantity is useful for blood glucose control.

One of the main alterations in people with diabetes is insulin resistance, which reduces the cells' ability to capture circulating glucose and affects liver metabolism, as a large portion of dietary carbohydrates is converted into fat. The ketogenic diet reduces carbohydrate intake, and various studies have shown that it improves glycemic control, hemoglobin A1c, and lipid markers.

Keys to cognitive enhancement and mental health on keto

As mentioned earlier, the body enters ketosis during extraordinary situations such as fasting, a low-carbohydrate diet, or after intense exercise. In these cases, ketones are an alternative source of energy for brain function when there is a deficiency of glucose, and they can pass through the blood-brain barrier.

Several studies have reviewed the possible positive effects of the ketogenic diet on brain function, especially in certain types of neurological deficiencies, traumatic injuries, among others. Preliminary results of its use in keto diets show improvements in cognitive aspects such as memory.

Getting Started with the Keto Diet: Practical Steps and Tips

More and more people are looking to adopt a healthy lifestyle and take care of their eating habits. Consequently, there is more information available, as well as emerging new nutritional trends and diets that can make it more challenging to choose the most suitable option for our health.

Establish a meal plan

European guidelines for managing overweight or obesity with the keto diet recommend the following criteria:

• General Protocol: intake of less than 30g of carbohydrates per day (~13% of total energy intake), with an increase in fat (44%) and protein (43%) intake, to total a daily caloric intake of <800 kcal. It should include high-quality protein (from peas, soy, and whey), natural foods, and dietary supplements. Each meal follows the following ratio: 18g of protein/4g of carbohydrates and 3g of fats (preferably unsaturated and mainly from vegetable oils with a high content of oleic acid) = 100-150 kcal.
• Active or initial stage: usually lasts between 8 and 12 weeks until there is a weight reduction according to the set goals. The total caloric intake is between 600-800 kcal divided into an intake of carbohydrates <50g (mainly vegetables), high-quality proteins of 0.8-1.2g/kg of weight, and fats (only 10g of olive oil). This stage includes the following dietary guidelines or ketogenic phases:
  • Phase 1: it is recommended to consume protein supplements with low glycemic index vegetables 4-5 times per day.
  • Phase 2: one of the portions of protein supplements is replaced with natural proteins such as meat/eggs/fish.
  • Phase 3: the intake of vitamins and minerals, including omega-3 fatty acids, is suggested.
• Reeducation or reintroduction stage: other food groups are gradually introduced, along with the guidance of a nutritionist. The recommended carbohydrates to consume are those with the lowest glycemic index (fruits and dairy), moving to a moderate level (legumes), and then to a high level (bread, pasta, and cereals), to achieve a total caloric intake between 800-1500 kcal/day.

Maintenance stage: it includes a nutritional program that ranges from 1500 to 2000 kcal/day, depending on the individual, and is balanced from the perspective of macronutrients and micronutrients. The main objective of this stage is long-term weight maintenance and promoting a healthy lifestyle.

These guidelines insist on the need to comprehensively evaluate the individual by a specialist professional in order to first assess the feasibility of following this diet and then establish control.

Allowed Foods in the Keto Diet

• Meat and Veggie Substitutes. Any type of meat is suitable for the keto diet (beef, pork, lamb, chicken...), as well as its substitutes such as tofu or tempeh. Processed meats and cold cuts can also be consumed. It is important to ensure they do not contain starches or breading.

• Fish and Seafood. The best option is fatty fish such as salmon and sardines, but white fish such as cod, trout, or sea bass are also suitable.
• Eggs in any form of cooking.
• Keto Vegetables, which are non-starchy vegetables. Leafy green vegetables are suitable, as well as others such as cauliflower, cabbage, broccoli, zucchini, cucumber, or celery.
• Acidic Fruits and Berries such as lemons, strawberries, raspberries, and cranberries with low sugar content.
• Nuts and Seeds are low in carbohydrates. The recommended daily portion is about 25 grams per day, and they should be additive-free.
• Cheeses and Full-Fat Dairy Products such as cheese, butter, or Greek yogurt.
• Fats and Sauces for cooking proteins, such as olive oil, and other salad dressings like mayonnaise.
• Black Coffee and Tea, which can be sweetened with calorie-free sweeteners.

Foods to Avoid or Limit in the Keto Diet

• Avoid sugary foods such as soft drinks, sweets, sports drinks, cookies, cakes, among others.
• Flavored Milk or Yogurts. Opt for plain yogurts to avoid added sugars, and milk since it also naturally contains sugars.
• Dietetic Products without Sugar or Low in Fat, as they tend to be rich in sugar alcohols, affect ketone levels, and may contain saturated fats and highly processed ingredients.
• Beans or Legumes due to their starch content, such as peas, beans, lentils, chickpeas, depending on the stage of the ketogenic diet you are in.
• Root Vegetables such as potatoes, sweet potatoes, carrots, etc., also contain starch. It depends on the stage of the ketogenic diet you are in.
• Avoid main sources of carbohydrates such as bread, cereals, rice, pasta, etc. It depends on the stage of the ketogenic diet you are in.
• Fruit except for the acidic ones mentioned earlier, due to their high sugar content.
• Alcohol due to its high carbohydrate content.

Tips for Success in the Keto Diet

Before making substantial changes to your diet, such as highly restrictive diets like the ketogenic diet, it is important to consult a specialist who can advise based on your health status.

"The key to any healthy diet, especially the ketogenic diet, is that it must be balanced in micronutrients and personalized," says Dr. Acosta. "It is not possible to generalize whether it is suitable or not, as each person has specific needs and does not respond in the same way to a dietary pattern".

Therefore, the keto diet is useful if it is properly controlled and meal planning is done to obtain the necessary nutrients.

Recommendations to Deal with Potential Side Effects

Any highly restrictive diet, such as the keto diet, is inherently unbalanced, so it is not recommended to maintain it in the long term. Long-term studies with this type of diet have not been conducted, with the maximum duration being around 12-24 weeks.

Therefore, if the main objective is weight loss, it is ideal to follow this diet for a few weeks and then, together with a nutritionist, evaluate the establishment of eating habits and the reintroduction of foods, along with regular exercise to maintain the desired weight.

If maintained for a long period of time, the ketogenic diet can lead to a higher risk of developing kidney stones, osteoporosis, and possible nutritional deficiencies if the appropriate foods are not included correctly in this diet. "To prevent this, it is important not to focus on eating high-fat foods, but to include a variety of meat, fish, nuts, fruit, and vegetables daily to ensure an adequate intake of vitamins and minerals, as well as fiber and protein," adds Yaiza. Proper nutritional advice will be crucial to minimize any nutritional deficiencies.

Another possible effect of the keto diet is an imbalance of water and minerals in the body, so taking mineral supplements such as sodium, potassium, and magnesium may be a suitable option to address this.

It is also important to note that this diet is not recommended for people with type 1 diabetes, during pregnancy and lactation, with kidney, heart, or respiratory insufficiency, elderly individuals, among others.

How to Deal with the First Weeks of the Keto Diet

Studies have shown that during the first 2-3 weeks, certain effects may occur with symptoms such as mental and physical fatigue, gastrointestinal discomfort (nausea, constipation), headaches, feeling hungry, dry mouth, or unpleasant taste, which are self-limiting as the body adapts to the calorie restriction. These symptoms are commonly known as "keto flu."

To minimize this, it is important to follow an individualized meal plan and consult with your nutritionist on how to alleviate these discomforts.

Myths and Realities about the Keto Diet

In recent years, the keto diet has gained popularity mainly due to the belief in rapid weight loss.

Due to its strict carbohydrate restriction, the keto diet often causes controversy as to whether it is recommended or simply a fad diet that has gained popularity in recent years. As a result, there are many myths about it that are not entirely accurate.

• The keto diet is not suitable for vegans. With proper planning and an adequate intake of vegetables and healthy plant-based fats, vegans can follow this diet.
• Ketosis is dangerous. With regular medical check-ups and under the supervision of nutrition specialists, this state is not dangerous to health.
• It is unhealthy. One of the main myths is that it has nutritional deficiencies, but this depends on the chosen foods, hence the importance of choosing lean proteins and unsaturated fats to obtain the necessary nutrients.
• You eat more fat and consume a high amount of protein on the keto diet. This is not entirely true, as the dietary pattern is based on an equitable intake of healthy fats and protein, limiting carbohydrates only.

If you want to learn more about nutrition...

• Nutrition Today: What diets are trendy and what does science say about them?
• Food Pyramid: How much do you know about it?
• Chitosan and Glucomannan: How do these allies work in weight loss diets?

Content prepared with the collaboration of Dr. Yaiza Acosta Chinea. This article is informative and does not replace the consultation with a specialist.

Healthcare Professionals