Ketogenic Diet (Keto Diet)

Medically Reviewed on 5/3/2022

What is the ketogenic diet?

 Ketogenic is a term for a low-carb diet
Ketogenic is a term for a low-carb diet.

The ketogenic diet is a diet that produces reactions in the body similar to those that occur during fasting. This is a type of extreme low-carb diet that was first developed in 1921 due to the ability of this type of diet to reduce or suppress seizures. As new medications to treat seizures were developed, the ketogenic diet became less popular as a way to manage seizure disorders. However, in 2008, a clinical trial showed that a ketogenic diet could help children with treatment-resistant epilepsy become seizure-free. A ketogenic diet is often prescribed for people who have failed two mainline anti-seizure drugs, with studies showing seizure-reduction rates as high as 85% after this treatment. It can be effective for patients of any age or seizure type. The reasons why a ketogenic diet works to help reduce seizures are unclear, but it is believed to induce metabolic changes that lower the risk of seizures.

The diet itself is a low-carb, high-fat diet that involves extreme reduction of carbohydrate consumption and replacing it with fat, up to a concentration of 70%-80% of calories from fat. There is no one standard ketogenic diet, and different ratios of nutrients have been used in so-called keto diets. All have in common the reduction of carbohydrates and an increase in fat along with a moderate amount of protein.

The reduction in carbohydrates deprives the body of glucose and causes a metabolic state known as ketosis, due to the accumulation of molecules known as ketones in the bloodstream. Ketones consist of acetoacetate, acetone, and beta-hydroxybutyrate and form in the liver from long- and medium-chain fatty acids when the body burns stored fat for energy after glucose is depleted or in situations in which there is inadequate insulin present for glucose to be used as energy. In addition to seizure disorders, ketogenic diets have been tested in the management of some people with other conditions including diabetes, cancer, polycystic ovary syndrome, and Alzheimer's disease.

Further, the "keto diet" has gained attention as a potential weight-loss tool. Its proponents argue that a carefully controlled ketogenic diet can avoid the dangers of ketoacidosis and be an effective way to lose weight.

What is ketosis?

Ketosis is the accumulation of ketone bodies or ketones in the blood. Ketosis occurs in healthy people during fasting and strenuous exercise. In excess, blood ketones can produce a toxic level of acid in the blood, referred to as ketoacidosis.

  • Ketoacidosis is a known and life-threatening complication of type 1 diabetes and has been described in some cases as healthy people eating a very low-carbohydrate diet.

What are different types of the ketogenic diet?

Since ketosis can be achieved in various ways, there are several types of the ketogenic diet:

  1. Standard ketogenic diet: This is the most popular version of the ketogenic diet and one with the most research. A standard ketogenic diet incorporates very low carbs (about 5%-10% of total calorie intake), moderate protein (about 20% of total calorie intake), and high fats (about 70%-75% of total calorie intake). This is the most recommended version for people seeking weight loss and blood sugar control.
  2. Targeted ketogenic diet: This type of ketogenic diet is mainly recommended for athletes to enhance their performance. In a targeted ketogenic diet, additional carbs are allowed around periods of extensive physical activity such as 30-45 minutes before an athletic event. Carbs should be easy to digest so that once the athletic event is finished, ketosis can be achieved with the conventional ketogenic dietary pattern.
  3. Cyclical ketogenic diet: Adhering to a ketogenic diet can be difficult. The cyclical pattern of a ketogenic diet makes it easier to follow. As the name suggests, a cyclical ketogenic diet, also called keto-cycling, involves ketogenic diet cycles interspersed with periods of higher carb intake. For example, the person may follow a ketogenic diet for five days of the week, and for the next two days, they can consume a higher amount of carbs. This version is best suited for people who find it too difficult to stick to the ketogenic diet.
  4. High-protein ketogenic diet: This version of a ketogenic diet is mainly suited to people with high protein requirements such as bodybuilders. It incorporates about 30%-35% protein, 60%-65% fats and 5% carbs.


According to the USDA, there is no difference between a “portion” and a “serving.” See Answer

What are foods to avoid with the ketogenic diet?

Since the keto diet is a low-carb diet plan, foods to avoid with the ketogenic diet include all carbohydrate sources, including both refined and unrefined products. Not only sugars but also whole-grain carbohydrates are not allowed.

Foods to avoid include:

  • All bread and cereals
  • Pasta
  • Cookies and baked goods
  • Rice
  • Processed foods (canned soups, all desserts, and all types of candy)
  • Starchy vegetables like corn and potatoes
  • Fruits and their juices

What foods are included in the ketogenic diet?

As discussed previously, the ketogenic diet includes high-fat foods and proteins and restricts carbohydrates. Since there is no one approved ketogenic diet, recommended foods and meal plans may differ.

Most ketogenic diets permit foods high in saturated fat, including:

  • Processed meats
  • Fatty cuts of meat, including red meat, lard, and butter
  • Unsaturated fats like oily fish, nuts, seeds, and plant oils

Should people take supplements while on the ketogenic diet?

The keto diet is a restrictive dietary pattern that involves avoiding various groups of nutritious foods including fruits, whole grains, and legumes. Since nutritional deficiencies are a risk factor with any ketogenic diet plan, it is important to work with a healthcare provider, including a nutritionist or dietitian, to ensure that all nutritional requirements are met. In some cases, this may involve taking vitamin or mineral supplements.

Some of the nutritional supplements that may be needed while on a keto diet include:

Who is a good candidate for the ketogenic diet?

The ketogenic diet is a recognized medical treatment for children and some adults with seizure disorders who have not responded to two different anti-seizure medications. Specific seizure disorders with multiple reports in the medical literature of benefits from the ketogenic diet include the following:

For people with certain other seizure disorders, the diet has also been suggested to be of benefit.

As a weight-loss tool, there is not adequate evidence to suggest that this diet is superior to other weight-control plans and may be associated with long-term risks or nutritional deficiencies.

Is the ketogenic diet safe? Health Benefit and Risks

The ketogenic diet has been shown in controlled studies to be effective in children and adults who have failed two lines of standard anti-seizure medication. However, it is not safe for use in people with certain genetic conditions that affect the metabolism of fatty acids. Nutritional deficiencies are a risk for any severely restricted diet, and in 2008 there was a report of two cases of sudden cardiac arrest in children who had been on the ketogenic diet for three years. Impairments in cardiac function may be due to deficiency in the mineral selenium from following the diet. Support from a dietitian or nutritionist may be required to help ensure that these and other potential nutrient deficiencies are addressed.

As a weight-loss measure, while there is some evidence to suggest that a ketogenic diet can be effective for weight control, there are also definitive health risks and complications associated with this low-carb, high-fat type of diet.

Some of the positive effects of the diet that have been described in addition to weight loss include:

  • Decreased food cravings due to the high-fat content decrease in the levels of hormones that stimulate appetite
  • Fat loss and an increase in calories burned

In some people, short-term following of a ketogenic diet has shown improvements in:

Overall, the health benefits of a ketogenic diet include:

  • Improved metabolism
  • Better hunger control
  • Improved muscle mass
  • Increased weight loss
  • Better blood sugar control 
  • Improved blood pressure
  • Reduced risk of cardiovascular diseases (due to improvements in various parameters including blood cholesterol, inflammatory markers and blood pressure)
  • Lowered insulin resistance
  • Better control of seizures in some cases

Furthermore, the extreme carbohydrate restriction of the keto diet may cause symptoms including:

It has also been proposed that the long-term side effects of this keto diet may include:

Currently, it remains unknown if the potential benefits of the keto diet for weight loss outweigh the health risks. It is recommended to eat whole foods, such as non-starchy vegetables, while on a keto diet to obtain adequate vitamins, minerals, and other antioxidants. Avoid eating processed foods to reduce any health risks. If you have certain health conditions such as eating disorders, pancreatic or liver disease, or chronic kidney disease, it is better to consult your doctor before you begin with a keto diet.

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Medically Reviewed on 5/3/2022
Harvard T.H. Chan School of Public Health. "Diet review: ketogenic diet for weight loss." <>.

Watson, John. "Ketogenic diet: Which patients benefit?" Mar. 20, 2018.