The ketogenic diet, often shortened to "keto," is a dietary approach characterized by high fat intake, moderate protein consumption, and very low carbohydrate intake. This dietary shift induces a metabolic state called ketosis, where the body primarily utilizes fat for energy instead of glucose. While initially developed as a therapeutic diet for epilepsy, the ketogenic diet has gained popularity as a weight-loss strategy and a potential treatment for various health conditions.
Historical Context and Development
Ancient Roots and Early Studies
The use of dietary modifications to treat diseases, including epilepsy, dates back to ancient Greece. Physicians like those of the Hippocratic Corpus recognized the potential of altering a patient's diet for therapeutic purposes.
The first modern study of fasting as a treatment for epilepsy was in France in 1911. Twenty epilepsy patients of all ages were "detoxified" by consuming a low-calorie vegetarian diet, combined with periods of fasting and purging. Two benefited enormously, but most failed to maintain compliance with the imposed restrictions.
In the early 20th century, fasting emerged as a treatment for epilepsy. Dr. Hugh William Conklin, an osteopathic physician, advocated for fasting to eliminate toxins believed to cause seizures. Neurologists in mainstream practice adopted Conklin's fasting therapy.
The Birth of the Ketogenic Diet
Building on fasting research, Dr. Russell Morse Wilder at the Mayo Clinic coined the term "ketogenic diet" in 1921 to describe a dietary approach that mimics the metabolic effects of fasting. Wilder aimed to create a sustainable dietary therapy that could provide the benefits of fasting without the associated limitations.
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The Classic Ketogenic Diet
Wilder's colleague, pediatrician Mynie Gustav Peterman, formulated the classic ketogenic diet. This diet, characterized by a 4:1 ratio of fat to combined protein and carbohydrates, became a standard treatment for pediatric epilepsy.
This classic ketogenic diet contains a 4:1 ketogenic ratio or ratio by weight of fat to combined protein and carbohydrate. This is achieved by excluding high-carbohydrate foods such as starchy fruits and vegetables, bread, pasta, grains, and sugar, while increasing the consumption of foods high in fat such as nuts, cream, and butter.
The MCT Ketogenic Diet
Most dietary fat is made of molecules called long-chain triglycerides (LCTs). However, medium-chain triglycerides (MCTs)-made from fatty acids with shorter carbon chains than LCTs-are more ketogenic. A variant of the classic diet known as the MCT ketogenic diet uses a form of coconut oil, which is rich in MCTs, to provide around half the calories.
In the 1960s, medium-chain triglycerides (MCTs) were found to produce more ketone bodies per unit of energy than normal dietary fats (which are mostly long-chain triglycerides). MCTs are more efficiently absorbed and are rapidly transported to the liver via the hepatic portal system rather than the lymphatic system.
Decline and Resurgence
The ketogenic diet's popularity waned with the introduction of effective anticonvulsant medications in the mid-20th century. However, the diet experienced a resurgence in the 1990s, driven by the advocacy of Jim Abrahams, whose son's epilepsy was successfully managed with the diet.
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In 1994, Hollywood producer Jim Abrahams, whose son's severe epilepsy was effectively controlled by the diet, created the Charlie Foundation for Ketogenic Therapies to further promote diet therapy. Publicity included an appearance on NBC's Dateline program and …First Do No Harm (1997), a made-for-television film starring Meryl Streep.
Understanding Ketosis
The Metabolic Shift
Normally, carbohydrates in food are converted into glucose, which is then transported around the body and is important in fueling brain function. However, if only a little carbohydrate remains in the diet, the liver converts fat into fatty acids and ketone bodies, the latter passing into the brain and replacing glucose as an energy source.
Ketosis is a metabolic state in which your body uses fat for fuel instead of carbs. It occurs when you significantly reduce your consumption of carbohydrates, limiting your body’s supply of glucose (sugar), which is the main source of energy for the cells.
Achieving Ketosis
Following a ketogenic diet is the most effective way to enter ketosis. Generally, this involves limiting carb consumption to around 20 to 50 grams per day and filling up on fats, such as meat, fish, eggs, nuts, and healthy oils (6). It’s also important to moderate your protein consumption. This is because protein can be converted into glucose if consumed in high amounts, which may slow your transition into ketosis (10).
Monitoring Ketosis
Blood, urine, and breath tests are available, which can help determine whether you’ve entered ketosis by measuring the amount of ketones produced by your body. Certain symptoms may also indicate that you’ve entered ketosis, including increased thirst, dry mouth, frequent urination, and decreased hunger or appetite.
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Types of Ketogenic Diets
There are several versions of the ketogenic diet, and what you eat depends on the type. They include:
- Standard ketogenic diet (SKD): This is a very low carb, moderate protein and high fat diet. It typically contains 70% fat, 20% protein, and only 10% carbs (9).
- Cyclical ketogenic diet (CKD): This diet involves periods of higher carb refeeds, such as 5 ketogenic days followed by 2 high carb days.
- Targeted ketogenic diet (TKD): This diet allows you to add carbs around workouts.
- High protein ketogenic diet: This is similar to a standard ketogenic diet, but includes more protein. The ratio is often 60% fat, 35% protein, and 5% carbs.
However, only the standard and high protein ketogenic diets have been studied extensively. Cyclical or targeted ketogenic diets are more advanced methods and primarily used by bodybuilders or athletes.
Applications of the Ketogenic Diet
Epilepsy Treatment
The ketogenic diet is a mainstream medical dietary therapy that was developed to reproduce the success and remove the limitations of the non-mainstream use of fasting to treat epilepsy. Although popular in the 1920s and '30s, it was largely abandoned in favour of new anticonvulsant drugs.
Epilepsy is considered refractory (not yielding to treatment) when two or three anticonvulsant drugs have failed to control it. The ketogenic diet is indicated as an adjunctive (additional) treatment in children and young people with drug-resistant epilepsy. It is approved by national clinical guidelines in Scotland, England, and Wales and reimbursed by nearly all US insurance companies.
Weight Loss
A ketogenic diet is an effective way to lose weight and lower risk factors for disease. In fact, research shows that the ketogenic diet may be as effective for weight loss as a low fat diet.
One review of 13 studies found that following a very low carb, ketogenic diet was slightly more effective for long-term weight loss than a low fat diet. People who followed the keto diet lost an average of 2 pounds (0.9 kg) more than the group that followed a low fat diet.
Another study in 34 older adults found that those who followed a ketogenic diet for 8 weeks lost nearly five times as much total body fat as those who followed a low fat diet (17).
Type 2 Diabetes Management
Diabetes is characterized by changes in metabolism, high blood sugar, and impaired insulin function (20). One older study found that the ketogenic diet improved insulin sensitivity by a whopping 75% (25).
Another study in 349 people with type 2 diabetes found that those who followed a ketogenic diet lost an average of 26.2 pounds (11.9 kg) over a 2-year period. What’s more, they also experienced improved blood sugar management, and the use of certain blood sugar medications decreased among participants throughout the course of the study (27).
Other Potential Benefits
Studies have now shown that the diet can have benefits for a wide variety of different health conditions:
- Heart disease: The ketogenic diet can help improve risk factors like body fat, HDL (good) cholesterol levels, blood pressure, and blood sugar.
- Cancer: The diet is currently being explored as an additional treatment for cancer, because it may help slow tumor growth.
- Alzheimer’s disease: The keto diet may help reduce symptoms of Alzheimer’s disease and slow its progression.
- Parkinson’s disease: Although more research is needed, one study found that the diet helped improve symptoms of Parkinson’s disease.
- Polycystic ovary syndrome: The ketogenic diet can help reduce insulin levels, which may play a key role in polycystic ovary syndrome.
- Brain injuries: Some research suggests that the diet could improve outcomes of traumatic brain injuries.
Foods to Include and Avoid
Foods to Avoid
Here’s a list of foods that need to be reduced or eliminated on a ketogenic diet:
- Sugary foods: soda, fruit juice, smoothies, cake, ice cream, candy, etc.
- Grains or starches: wheat-based products, rice, pasta, cereal, etc.
- Fruit: all fruit, except small portions of berries or strawberries
- Beans or legumes: peas, kidney beans, lentils, chickpeas, etc.
- Root vegetables and tubers: potatoes, sweet potatoes, carrots, parsnips, etc.
- Low fat or diet products: low fat mayonnaise, salad dressings, and condiments
- Some condiments or sauces: barbecue sauce, honey mustard, teriyaki sauce, ketchup, etc.
- Unhealthy fats: processed vegetable oils, mayonnaise, etc.
- Alcohol: beer, wine, liquor, mixed drinks
- Sugar-free diet foods: sugar-free candies, syrups, puddings, sweeteners, desserts, etc.
Foods to Include
You should base the majority of your meals around these foods:
- Meat: red meat, steak, ham, sausage, bacon, chicken, and turkey
- Fatty fish: salmon, trout, tuna, and mackerel
- Eggs: pastured or omega-3 whole eggs
- Butter and cream: grass-fed butter and heavy cream
- Cheese: unprocessed cheeses like cheddar, goat, cream, blue, or mozzarella
- Nuts and seeds: almonds, walnuts, flaxseeds, pumpkin seeds, chia seeds, etc.
- Healthy oils: extra virgin olive oil, and avocado oil
- Avocados: whole avocados or freshly made guacamole
- Low carb veggies: green veggies, tomatoes, onions, peppers, etc.
- Condiments: salt, pepper, herbs, and spices
Potential Side Effects and Mitigation Strategies
Although the ketogenic diet is usually safe for most healthy people, there may be some initial side effects while your body adapts. There’s some anecdotal evidence of these effects often referred to as the keto flu (38).
Reported keto flu symptoms include diarrhea, constipation, and vomiting. Other less common symptoms include:
- Poor energy and mental function
- Increased hunger
- Sleep issues
- Nausea
- Digestive discomfort
- Decreased exercise performance
To minimize this, you can try a regular low carb diet for the first few weeks. This may teach your body to burn more fat before you completely eliminate carbs.
A ketogenic diet can also change the water and mineral balance of your body, so adding extra salt to your meals or taking mineral supplements may help. Talk to your doctor about your nutritional needs.
Long-Term Considerations and Potential Risks
While the keto diet has its benefits, staying on it in the long term may have some negative effects, including risks of the following:
- Low protein in the blood
- Extra fat in the liver
- Kidney stones
- Micronutrient deficiencies
A type of medication called sodium-glucose cotransporter 2 (SGLT2) inhibitors for type 2 diabetes can increase the risk for diabetic ketoacidosis, a dangerous condition that increases blood acidity. Anyone taking this medication should avoid the keto diet.
The Spanish Ketogenic Mediterranean Diet (SKMD)
The ketogenic diet has been adapted to incorporate elements of the Mediterranean diet, resulting in the "Spanish Ketogenic Mediterranean Diet" (SKMD). This variation emphasizes virgin olive oil as the primary fat source, moderate red wine consumption, and the inclusion of green vegetables, salads, and fish.
This protein ketogenic diet was called "Spanish Ketogenic Mediterranean Diet" (SKMD) due to the incorporation of virgin olive oil as the principal source of fat, moderate red wine intake, green vegetables and salads as the main source of carbohydrates and fish as the main source of proteins.
Benefits of the SKMD
A prospective study involving obese subjects demonstrated that the SKMD led to significant reductions in body weight, body mass index, blood pressure, cholesterol levels, and glucose levels. The SKMD is considered a safe and effective approach for weight loss, promoting a non-atherogenic lipid profile, lowering blood pressure, and improving fasting blood glucose levels.
There was an extremely significant reduction in body weight, body mass index, systolic blood pressure, diastolic blood pressure, total cholesterol and glucose. There was a significant reduction in LDLc and an extremely significant increase in HDLc. The SKMD is safe, an effective way of losing weight, promoting non-atherogenic lipid profiles, lowering blood pressure and improving fasting blood glucose levels.
Key Components of the SKMD
The healthy properties of the incorporation of olive oil, red wine and fish consumption to a ketogenic diet could be explained by the 3 following sections.
- Olive Oil: Considered the pillar of the Mediterranean diet, olive oil improves cardiovascular risk factors, modulates endothelial function, inflammation, and oxidative stress.
- Red Wine: The combination of ethanol and phenolic compounds in red wine is thought to be responsible for the apparent protective cardiovascular effect.
- Fish: The omega-3 polyunsaturated fatty acids (EPA and DHA) found in fish increase insulin sensitivity and reduce inflammatory markers.
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