Ketogenic diet (keto diet) facts
- The ketogenic diet is a high-fat diet that drastically restricts carbohydrates. It produces a reaction in the body that is similar to the fasting state.
- The low-carb, high-fat keto diet causes the metabolic state known as ketosis, in which substances known as ketones or ketone bodies accumulate in the blood. These are the same substances that accumulate during ketoacidosis in people with type 1 diabetes.
- A ketogenic diet has been shown to be effective in treating seizure disorders that have not responded to two different antiseizure medications. While this treatment is most often used in children, some adults with seizure disorders may also be helped by a ketogenic diet.
- A ketogenic diet is typically not recommended for weight control because it is not superior to other more standard weight management plans and may be associated with health risks, including nutritional deficiencies.
- Ketogenic diets have been the subject of research to determine if they have value in managing other conditions including cancer and diabetes, but there is currently no recommendation for this practice.
Ketosis and the Ketogenic Diet
When you eat less than 50 grams of carbs a day, your body eventually runs out of fuel (blood sugar) it can use quickly. This typically takes 3 to 4 days. Then you'll start to break down protein and fat for energy, which can make you lose weight. This is called ketosis.
What is the ketogenic 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 antiseizure 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.
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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 of healthy people eating a very low-carbohydrate diet.
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Is the ketogenic diet safe? What are the health benefits and risks of the
The ketogenic diet has been shown in controlled studies to be effective in children and adults who have failed two lines of standard antiseizure 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 dietician 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, decreases 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 blood pressure, cholesterol levels, and blood sugar, but these effects are similar to those seen with conventional weight loss programs.
Further, the extreme carbohydrate restriction of the keto diet may cause symptoms including hunger, depressed mood, constipation, headache, and irritability. It has also been proposed that long-term effects of this diet may include osteoporosis and an increased risk for kidney stones and gout. Currently, it remains unknown if the potential benefits of the keto diet for weight loss outweigh the health risks.
According to the USDA, there is no difference between a “portion” and a “serving.”
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 meals 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 are also typically included.
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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 breads and cereals, pasta, cookies and baked goods, rice, starchy vegetables like corn and potatoes, and fruits and their juices.
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Should people take supplements while on the ketogenic diet?
Since nutritional deficiencies are a risk factor with any ketogenic diet plan, it is important to work with a health care provider, including a nutritionist or dietician, to ensure that all nutritional requirements are met. In some cases, this may involve taking vitamin or mineral supplements.
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 that have not responded to two different antiseizure medications. Specific seizure disorders with multiple reports in the medical literature of benefit from the ketogenic diet include the following:
For people with certain other seizures 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.
Medically Reviewed on 8/8/2019
Harvard T.H. Chan School of Public Health. "Diet review: ketogenic diet for
weight loss." <https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/ketogenic-diet/>.
Watson, John. "Ketogenic diet: Which patients benefit?" Medscape.com. Mar. 20, 2018.