Last updated: August 30, 2021

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Ketogenic diets, better known as "keto", have grown massively in popularity in recent years, especially as a weight loss method. Though you might think you're looking at a new way of eating, the keto diet actually has medical origins and has been used to treat epilepsy and other serious conditions.

This diet involves high fat consumption, moderate protein consumption, and virtually no carbohydrates. Its goal is to stimulate fat oxidation and produce large amounts of ketonic bodies which eventually become fuel for cells. Are you curious what science has to say about the keto diet? This guide will explain it all.




Key Facts

  • The keto diet is based on fat consumption. Fat may represent anywhere from 70 to 90% of the calories consumed, depending on your goal. This diet has neuroprotective effects (particularly in people with epilepsy), creates healthier metabolism, and promotes healthier weight.
  • To incentivize ketonic body production, the keto diet excludes foods high in simple and complex carbs: fruits, grains, legumes, and many vegetables. As a consequence, you may have insufficient intake of fiber, flavonoids, vitamins, and minerals. Dietary supplements of vitamin C, potassium, magnesium, and fiber may be required.
  • Anyone deciding to follow the keto diet responsibly must ask a specialist, plan their meals and grocery shopping, and be patient while their body adjusts to using ketonic bodies as an energy source.

The Best Supplements for a Keto Diet: Our Selection

When you follow a keto diet (unless only doing so in the short term), nutritional deficiencies may result. These deficiencies are related to the restrictions this diet places on important food groups like fruit, vegetables, grains, and legumes. As such, let's look at the best supplements available for keto dieters:

Buyer's Guide: What You Need to Know About the Keto Diet

Keto diets’ distribution of nutrients is extremely different from conventional diets, because its goal is for the body to use fat as fuel.

The keto diet is based on fat consumption. Fat may represent anywhere from 70 to 90% of the calories consumed, depending on your goal. (Source: Lightfieldstudios: 131260981/ 123rf.com)

What Is the Keto Diet?

In a keto diet, fat represents 70 to 90% of the total calories consumed. Protein intake is moderate, while carb intake is drastically restricted. This induces the body to enter a state of ketosis, meaning it burns fat as an energy source  (1, 2).

With typical eating habits, glucose (a carbohydrate) is cells' primary fuel source. In response to a keto dieter's lack of carbohydrates, cells instead begin to oxidize "burn" fats. Ketonic bodies are produced as a result, and these serve as an energy source. This is when we say that the body is in ketosis (1).

Many people follow the keto diet with fat burning and weight loss as their objective. However, this special regimen came about as a treatment for refractory epilepsy (epilepsy which doesn't respond to medication) in children and teens. For these people, keto diets notably reduces their number of seizure episodes (1, 2, 3).

Macronutrients Keto Diet Conventional Diet
Fat 70 - 90% 25 - 30%
Protein 10 - 20% 15 - 20%
Carbohydrates No more than 5 -10% . In strict keto diets, no more than 20 grams per day. 55 - 60%

What Do Ketonic Bodies Do?

Keto diets simulate prolonged fasting. Because of this effect, fat is used as the body's main energy source. The lack of carbohydrates (namely, glucose) stimulates ketogenesis, or the mass production of three ketonic bodies: acetone, acetoacetate, and β-hydroxybutyrate. When you consume carbohydrates, whether simple or complex, the body leaves the ketosis state (1, 4).

Ketonic bodies become the raw fuel source for the brain, heart, and muscles (4).

In people with certain medical conditions, neurons cannot use glucose as an energy source, which leads to seizures. In these cases, ketonic bodies provide energy and reduce the disease's symptoms. On the other hand, many people follow a keto diet for weight loss because ketonic bodies have appetite-suppressing effects (1, 5).

To incentivize ketonic body production, the keto diet excludes foods high in simple and complex carbs: fruits, grains, legumes, and many vegetables. (Source: Elena: 43428392/ 123rf.com)

What Are Keto's Health Benefits?

The ketogenic diet is noted for its neuroprotective effects in people with refractory epilepsy, GLUT-1 transporter deficiency, and pyruvate dehydrogenase (PDH) deficiency. However, most keto dieters are simply looking to lose weight and shed fat. The keto diet's benefits are (6, 7):

  • Lowering the frequency and duration of seizures in people with refractory epilepsy (epilepsy which doesn't respond to medications), especially children and adolescents (2, 6).
  • Alleviates symptoms of pyruvate dehydrogenase deficiency and GLUT-1 transporter deficiency (2, 6).
  • Promotes weight loss by reducing body fat. Keto diets stimulate fat oxidation, or "burning", for the body to produce energy. Simultaneously, it inhibits body fat synthesis. Plus, ketonic bodies suppress appetite, helping reduce your caloric intake (7).
  • May slow tumor growth, since tumor cells may not have the capacity to use ketonic bodies that normal cells have. However, results on this are still not conclusive. Further research is needed on keto diets' possible cancer-related benefits (2, 7).
  • Promotes healthy metabolism. The keto diet is associated with improved sensitivity to insulin and better blood sugar control. It's also related to reduced levels of lipids (cholesterol and tryglycerides) in the bloodstream, as well as reduced inflammation (8).
  • May prevent neurodegenerative illnesses like Alzheimer's disease, Parkinson's disease, and multiple sclerosis (2, 7).

Keto diets’ distribution of nutrients is extremely different from conventional diets, because its goal is for the body to use fat as fuel. (Source: Gkrphoto: 104073542/ 123rf.com)

What Foods Are Allowed in a Keto Diet?

Going on a keto diet involves eliminating almost all foods which contain carbohydrates and consuming large amounts of fat from vegetable and animal sources. The ideal carhohydrate intake is around 20 grams a day, and the maximum is around 50 grams a day. This table lays out the foods which a keto diet allows and prohibits (2):

Permitted Food Prohibited Food
- Sunflower oil, olive oil, coconut oil
- Avocado
- Beef, poultry, pork, fish, and shellfish
- Cold cuts and processed meat
- Butter and margarine
- Hard and semi-hard cheeses, aged cheeses high in fat
- Cream cheese
- Natural full-fat yogurt (in small amounts)
- Cream
- Moderate amounts of leafy vegetables (spinach, Swiss chard, lettuce), onions, tomatoes, cabbage, Brussels sprouts, asparagus, peppers, celery, cauliflower, broccoli
- Eggs
- High-fat condiments like mayonnaise or Caesar dressing
- Nuts (walnuts, hazelnuts, almonds, cashews) and seeds
- Coffee, black tea, herbal tea
- Zero-calorie sweeteners like stevia
- Berries, kiwi, and citrus in small amounts (e.g. half a kiwi or three strawberries)
- Vegetarian 'milks' derived from nuts (e.g. cashew milk, almond milk)
- Olives
- Salt, pepper, herbs and spices
- High-calorie sweeteners like sugar, muscovado, honey, coconut sugar, and maple syrup
- Potatoes, sweet potatoes, rice, oats, legumes
- Flour and products made with flour (bread, pasta, cookies, cakes)
- Fruit, especially fruits high in carbohydrates like bananas, grapes, mangoes, and figs (exception made for small amounts of berries)
- Dried fruits (raisins, apricots)
- Sweet vegetables like carrots, squash, and beets
- Milk and sweetened yogurt (exception made for occasional splash of whole milk in coffee or tea)
- Sugary drinks and fruit juice
- Candy, chocolate, ice cream, other desserts
- Beer, cider, sweet wines, and most alcoholic beverages

What Are Keto's Side Effects?

Keto diets may cause some mild side effects during the initial adjustment phase as cells have still not grown accustomed to using ketonic bodies as fuel. These can include dizziness, headaches, and fatigue. Other unwanted reactions may be more serious and could require you to stop your keto diet (2, 7):

  1. Metabolic acidosis, a very serious condition common in people with type 1 diabetes. Ketonic bodies accumulate in the bloodstream and acidify, creating an imbalance which may become fatal.
  2. Vomiting
  3. Constipation
  4. Hypoglycemia (low blood sugar)
  5. Drastically weakened mental and physical performance
  6. Delayed growth in children
  7. Pancreatitis
  8. Kidney stones
  9. Irregular heart rate
  10. Increased uric acid and gout

Who Shouldn't Go on a Keto Diet?

There are several groups who are advised not to go on keto diets. Some of these recommendations are related to pre-existing medical conditions; others stem from a lack of data about whether keto is safe during certain development stages. These groups should not attempt this diet regimen (2, 6, 7):

  1. Pregnant or breastfeeding women
  2. People with disorders which affect fat oxidation on a mitochondrial level
  3. People with unmanaged type 1 or type 2 diabetes
  4. People with conditions affecting fatty acid synthesis
  5. People with porphyria
  6. People with enzyme deficiencies involved in various metabolic reactions (pyruvate carboxylase deficiency, acyl-CoA dehydrogenase deficiency)
  7. People with primary carnitine deficiency
  8. People with liver disease, kidney disease, or severe heart disease

Keto Diet F.A.Q.

How long can I stay on a keto diet?

Keto diets may be followed anywhere from a 2-4 week period to several years. Children with refractory epilepsy follow this diet for long periods because it's a treatment which reduces or eliminates their seizures. It's important to clarify that once someone losing weight stops their keto diet, the weight lost tends to return in a rebound effect.

Are keto diets recommended for athletes?

Athletes require carbohydrates to achieve high performance. This applies to both resistance athletes like marathon runners or cyclists and strength-based athletes like lifters. Some ketogenic diets allow carbohydrates during workouts. Others alternate keto days with days of normal carb intake (a cyclical keto diet).

Start your keto diet by trying cauliflower hummus, cloud bread, and almond-based brownies.
(Source: Thitarees: 89937142/ 123rf.com)

Do keto diets have a risk of nutrient deficiencies?

Yes. If keto diets are followed for months or years, various nutrient deficiencies are common consequences. These include basic nutrients like vitamin D, C, and some B vitamins, minerals like magnesium, potassium, and calcium, dietary fiber, and flavonoids. The lack of fruits and vegetables in a keto diet is the culprit for many nutritional deficiencies.

Can vegans go on a keto diet?

No, keto diets are not recommended for vegans. Most of the foods high in vegetable proteins are also high-carb. Because vegetable protein is crucial for vegans, these nutrients cannot be eliminated, and a ketosis state will not be possible. A vegan keto diet would be incredibly restrictive and risky for your health.

Summary

The keto diet - high fat, moderate protein, and practically no carbohydrates - is more than just a way of eating. Though it's traditionally been used to treat refractory epilepsy, all the evidence shows that more and more people are adopting it as their permanent lifestyle to lose weight and shed body fat.

Doctors, nutritionists, and dieticians must be properly trained and educated to accompany their patients through a keto diet and guide them safely. Because keto dieters often don't get enough fiber, vitamins, and minerals, it's not surprising that they need to take supplements.

If you enjoyed this guide to keto diets and supplements, feel free to share it on social media or leave us a comment about your keto experiences.

(Featured image source: Elena: 73882014/ 123rf.com)

References (12)

1. Metaanálisis. Freeman J et al. The Ketogenic Diet: From Molecular Mechanisms to Clinical Effects [Internet]. 2006.
Source

2. Artículo científico. Amado Salvatierra J et al. Dieta cetogénica. Aspectos clínicos. Aplicación dietética [Internet]. 2012.
Source

3. Metaanálisis. Henderson B et al. Efficacy of the Ketogenic Diet as a Treatment Option for Epilepsy: Meta-analysis [Internet]. 2006.
Source

4. Artículo científico. Owen O. Ketone bodies as a fuel for the brain during starvation [Internet]. 2006.
Source

5. Artículo científico. Covarrubias P, Aburto M, Sámano L. Dietas cetogénicas en el tratamiento del sobrepeso y la obesidad [Internet]. 2013.
Source

6. Artículo científico. Halevy A, Peleg-Weiss L, Cohen R, Shuper A. An Update on the Ketogenic Diet [Internet]. 2012.
Source

7. Artículo científico. Paoli A, Rubini A, Volek J, Grimaldi K. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets [Internet]. 2013.
Source

8. Artículo científico. Gershuni V, Yan S, Medici V. Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome [Internet]. 2018.
Source

9. Artículo científico. Pesta D, Samuel V. A high-protein diet for reducing body fat: mechanisms and possible caveats [Internet]. 2014.
Source

10. Artículo científico. Carroll J, Koenigsberger D. The Ketogenic Diet: A Practical Guide for Caregivers [Internet]. 1998.
Source

11. Ensayo clínico. Bergqvist C et al. Fasting versus Gradual Initiation of the Ketogenic Diet: A Prospective, Randomized Clinical Trial of Efficacy [Internet]. 2005.
Source

12. Artículo científico. Harvey K, Holcomb L, Kolwicz S. Ketogenic Diets and Exercise Performance [Internet]. 2019.
Source

Why you can trust me?

Scientific article
Metaanálisis. Freeman J et al. The Ketogenic Diet: From Molecular Mechanisms to Clinical Effects [Internet]. 2006.
Go to source
Scientific article
Artículo científico. Amado Salvatierra J et al. Dieta cetogénica. Aspectos clínicos. Aplicación dietética [Internet]. 2012.
Go to source
Meta-analysis
Metaanálisis. Henderson B et al. Efficacy of the Ketogenic Diet as a Treatment Option for Epilepsy: Meta-analysis [Internet]. 2006.
Go to source
Scientific article
Artículo científico. Owen O. Ketone bodies as a fuel for the brain during starvation [Internet]. 2006.
Go to source
Scientific article
Artículo científico. Covarrubias P, Aburto M, Sámano L. Dietas cetogénicas en el tratamiento del sobrepeso y la obesidad [Internet]. 2013.
Go to source
Scientific article
Artículo científico. Halevy A, Peleg-Weiss L, Cohen R, Shuper A. An Update on the Ketogenic Diet [Internet]. 2012.
Go to source
Scientific Review
Artículo científico. Paoli A, Rubini A, Volek J, Grimaldi K. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets [Internet]. 2013.
Go to source
Scientific article
Artículo científico. Gershuni V, Yan S, Medici V. Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome [Internet]. 2018.
Go to source
Scientific article
Artículo científico. Pesta D, Samuel V. A high-protein diet for reducing body fat: mechanisms and possible caveats [Internet]. 2014.
Go to source
Scientific article
Artículo científico. Carroll J, Koenigsberger D. The Ketogenic Diet: A Practical Guide for Caregivers [Internet]. 1998.
Go to source
Clinical Trial
Ensayo clínico. Bergqvist C et al. Fasting versus Gradual Initiation of the Ketogenic Diet: A Prospective, Randomized Clinical Trial of Efficacy [Internet]. 2005.
Go to source
Scientific article
Artículo científico. Harvey K, Holcomb L, Kolwicz S. Ketogenic Diets and Exercise Performance [Internet]. 2019.
Go to source
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