Keto Diet: How It Works, Foods Allowed & Diet Plan

The ketogenic diet consists of a drastic reduction in the intake of carbohydrates. For this reason one should avoid eating bread and rice, opting for the consumption of lean meats and fats. As long as this diet is supervised by a nutritionist, 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, it is also being researched as an anti-cancer treatment as cancer cells feed off carbohydrates, which is the food group the ketogenic diet does not include.

It is important for the diet to be done only under the supervision and guidance of a nutritionist. This is so that you can have a complete nutritional assessment to find out whether you can do the diet.

Keto Diet: How It Works, Foods Allowed & Diet Plan

How Does the Keto Diet Works

The ketogenic diet comprises 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 up your intake of fat significantly. This means eating foods such as avocado, coconut, seeds, cream, olive oil, peanuts, chestnuts, walnuts, and almonds. The quantity of protein in your diet should also increase until it comprises 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 though, 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 a much 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 


Milk and 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 bladder stones or anyone taking medications that contain cortisone.

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

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  • BOISOM, Detlev. New insights into the mechanisms of the ketogenic diet.. Curr Opin Neurol. Vol.30(2). 187-192, 2017
  • SANYAI Kalra et al. The Ketogenic Diet. US Endocrinology. 2. 14; 62-64, 2018
  • WALCZYK, Thomas; WICK, Jeannette Y. The Ketogenic Diet: Making a Comeback. The Consultant Pharmacist. Vol.32(7). 388-396, 2017
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