What is a Ketogenic Diet (Foods Allowed & Diet Plan)

February 2022

The ketogenic diet, commonly known as the keto diet, consists of a drastic reduction in the intake of carbohydrates.  Eating carb-heavy foods, like bread and rice is often avoided and replaced with the consumption of lean meats and fats. As long as this diet is supervised by a registered dietitian, it can be a good alternative for those who wish to lose weight, as the body starts using its own fat stores as a source of energy, instead of the carbohydrates that come from food. 

This diet is especially known for helping to control and prevent epileptic seizures. However, studies are currently being done to support it as a complement to cancer treatment, as cancer cells often feed off of carbohydrates

It is important for the diet to be done only under the supervision and guidance of a dietitian. He or she can complete a thorough nutritional assessment to evaluate whether you are a good candidate for this diet.

How it Works

The ketogenic diet involves a drastic reduction of carbohydrates, which will make up only 10 to 15% of total daily calories. However, this quantity may vary according to your health condition, how long the diet will last, and your dietary goals.  

To compensate for the reduction in carbohydrates, you will need to significantly increase your intake of fat. This means eating foods like avocado, coconut, seeds, olive oil, peanuts, chestnuts, walnuts, and almonds. The quantity of protein in your diet should also increase until it makes up 20% of daily calories. It is, therefore, necessary that you eat meat, chicken, or fish at lunch and dinner and that you have eggs and cheese for snacks.

When you start this diet, your body will go through an adaptation period which can last from several days to a few weeks and it happens because your body switches to producing energy through fat, instead of carbohydrates. So it is possible that in the first days you will have symptoms such as exhaustion, lethargy, and headaches. These will disappear once the body has adapted. 

Another similar diet to the keto diet is the low-carb diet, the major difference being that in the keto diet there is an even higher restriction of carbohydrates. 

"Keto Foods" and Foods To Avoid

The following table lists the foods that are allowed in the keto diet and the ones that are forbidden.

Keto Foods/Allowed

Foods To Avoid

Red meat, chicken, eggs, and fish

Rice, pasta, corn, cereal, oats, and cornstarch

Olive oil, coconut oil, butter, pork fat 

Beans, soy, peas, lentils, and chickpeas

Cream, cheese, coconut milk, and almond milk

Wheat flour, bread, toast, and most salty snacks

Peanuts, nuts, hazelnuts, Brazil nuts, almonds, peanut butter, almond butter

White potato, sweet potato, cassava, yam, parsnips

Fruit such as strawberries, raspberries, blackberries, olives, avocado or coconut 

Cakes, desserts, biscuits, chocolate, candies, ice-cream, chocolate milk

Vegetables and greens, such as spinach, lettuce, broccoli, cucumber, onion, zucchini, cauliflower, asparagus, red chicory, white cabbage, Bok Choy, celery or bell pepper

Refined sugar, muscovado sugar

Flaxseeds, chia seeds, sunflower seeds  

Chocolate powder, milk 


Alcoholic drinks 

In this type of diet, whenever you eat processed food it is very important to check the nutrition facts label to check if there are carbohydrates and in which quantity, so as not to exceed the daily quantity.

3-Day Keto Diet Plan

The following table contains an example of a three-day keto diet meal plan:


Day 1

Day 2

Day 3


Eggs fried in butter  +  mozzarella cheese

Omelette made with 2 eggs and vegetable filling  + 1 cup of strawberry juice with 1 teaspoon of flaxseeds 

Smoothie made with avocado, almond milk and ½ tablespoon of chia seeds

Morning snack

Almonds + 3 slices of avocado

Strawberry smoothie with coconut milk + 5 walnuts

10 raspberries + 1 tablespoon of peanut butter 



Salmon with asparagus  + avocado + olive oil

Vegetable salad with lettuce, onion and chicken  + 5 cashew nuts + olive-oil + Parmesan cheese

Meatballs with courgette noodles and Parmesan cheese 

Afternoon snack

10 cashew nuts 2 tablespoons coconut chips  + 10 strawberries

Eggs fried in butter + rennet cheese

Scrambled eggs with oregano and grated Parmesan

It is important to remember that the keto diet should be prescribed by a nutritionist.

What Is a Cyclical Ketogenic Diet?

A cyclical ketogenic diet helps to maintain diet follow-through and good weight loss, as well as providing energy for physical exercise. 

In this type of keto diet, you follow the keto diet meal plan for five consecutive days, and then you have two days when you can eat carbohydrates, such as bread, rice, and pasta. However, desserts, ice-creams, cakes, and other sugar-rich products should continue being off-limits.

Possible Side Effects

The ketogenic diet is not advised for those over 65, children and teenagers, and pregnant and breastfeeding women. It should also be avoided by those who have an increased risk of ketoacidosis, such as type 1 diabetics, uncontrolled type 2 diabetics, people with low weight, or with a history of liver or kidneys diseases and cardiovascular alterations, such as a stroke. It is also not recommended for those with kidney stones or anyone taking medications that contain cortisone.

In these cases, the ketogenic diet will need to be approved by a doctor and followed-up by a dietitian. 

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Edited by Tua Saude editing team in February 2022. Clinical review completed by Tatiana Zanin - Registered Dietitian in February 2022.


  • BOISOM, Detlev. New insights into the mechanisms of the ketogenic diet.. Curr Opin Neurol. Vol.30(2). 187-192, 2017
  • WALCZYK, Thomas; WICK, Jeannette Y. The Ketogenic Diet: Making a Comeback. The Consultant Pharmacist. Vol.32(7). 388-396, 2017
Show more references
  • SANYAI Kalra et al. The Ketogenic Diet. US Endocrinology. 2. 14; 62-64, 2018
Clinical review:
Tatiana Zanin
Registered Dietitian
Graduated in Clinical Nutrition in 2001 and has a Master’s in Clinical Nutrition. Licensed to practice under the CRN-3 in Brazil and the ON in Portugal