The ketogenic diet, often shortened to "keto," has surged in popularity as a weight-loss strategy and potential therapy for various health conditions. This high-fat, very low-carbohydrate diet shifts the body's primary fuel source from glucose to fat, inducing a metabolic state called ketosis. While the keto diet has demonstrated promising results in certain contexts, it's crucial to understand its principles, potential benefits, and possible risks before making drastic dietary changes.
Origins and Evolution of the Ketogenic Diet
The ketogenic diet was developed in 1921 by Dr. Russell Wilder. The medical setting premiered the ketogenic diet in 1921 by Dr. Wilder, who also coined the term "ketogenic diet". The diet was originally intended to treat children diagnosed with epilepsy, and effects were first noticed in response to fasting. In the early 2000s, diets such as Atkins, South Beach and Paleo attracted people looking for quick weight loss. Through his observations, Wilder noticed the diet reduced the frequency and intensity of seizures in a subset of his patients who followed this dietary approach.
How the Ketogenic Diet Works: Inducing Ketosis
The fundamental principle of the ketogenic diet lies in drastically reducing carbohydrate intake, which forces the body to seek alternative fuel sources. Normally, the body relies heavily on a steady supply of glucose (carbs) for fuel. Carbohydrates in food are converted into glucose, which is then transported around the body and is important in fueling brain function. When carbohydrate intake is restricted to less than 50 grams daily, insulin secretion decreases significantly, leading the body into a catabolic state. As a result, glycogen stores are depleted, triggering a series of metabolic changes.
In the absence of sufficient glucose, the liver begins breaking down fat tissue for fuel in the form of free fatty acids. This process produces ketones, or ketone bodies, which become the body and brain’s main source of energy. Ketones are produced in the liver. These ketone bodies (ie, acetoacetate, beta-hydroxybutyrate, and acetone) accumulate in the body as the ketogenic diet is sustained and serve as an alternative energy source for the body. Ketone bodies can also cross the blood-brain barrier to provide an alternative energy source for the brain. RBCs and the liver do not utilize ketones due to a lack of mitochondria and enzyme diaphorase.
This metabolic state is referred to as "nutritional ketosis." As long as the body is deprived of carbohydrates, the metabolism remains ketotic. Nutritional ketosis is generally considered safe since it involves the production of ketone bodies in moderate concentrations without significantly impacting blood pH. Nutritional ketosis differs from ketoacidosis, a severe and life-threatening condition characterized by excessively high levels of ketone bodies, leading to acidosis in the blood.
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Macronutrient Ratios and Food Choices on the Keto Diet
A ketogenic diet primarily consists of high fat intake, moderate protein consumption, and low carbohydrate intake. The macronutrient distribution typically ranges from approximately 55% to 60% fat, 30% to 35% protein, and 5% to 10% carbohydrates. The original ketogenic diet derived 70-75% of all calories from fat, 20-25% of calories from protein and 5-10% from carbohydrates. A standard keto diet consists of 70% to 80% fats, 10% to 20% proteins and 5% to 10% carbohydrates.
This translates to severely limiting carbohydrate-rich foods such as rice, pasta, bread, fruit and potatoes. The keto diet excludes carb-rich foods like grains, beans, fruits and starchy vegetables. Instead, the diet emphasizes consumption of foods high in fat such as nuts, cream, and butter. The types of foods that provide fat for the keto diet include: Meats and fish, Eggs, Nuts and seeds, Butter and cream, Cheese and Oils such as olive oil and canola oil.
Variations of the Ketogenic Diet
While the standard ketogenic diet (SKD) is the most common, several variations exist to suit different needs and preferences:
- 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.
- 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.
Potential Benefits of the Ketogenic Diet
The ketogenic diet has demonstrated potential benefits in various areas, including:
Weight Loss
One of the biggest benefits of ketosis may be weight loss. A meta-analysis of 11 studies found that the low-carbohydrate diet group experienced considerable weight reductions compared to the low-fat diet group. Individuals assigned to a very low-carbohydrate ketogenic diet (VLCKD) experienced decreases in body weight, triglycerides, and diastolic blood pressure, as well as increases in HDL-C and LDL-C. A meta-analysis of randomized controlled trials (RCTs) revealed that the ketogenic diet is particularly effective in improving metabolic parameters related to glycemic control, weight management, and lipid control in obese individuals, particularly those with preexisting diabetes. Compared to low-fat diets, the ketogenic diet demonstrated superior outcomes in terms of glycemic control, weight loss, and lipid markers. The ketogenic diet also showed positive effects on insulin resistance and lipid markers, suggesting it can improve metabolic markers independent of weight loss. The process can help you feel less hungry, which may lead to eating less food. It can help you lose belly fat (visceral fat) while maintaining a lean mass.
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Management of Type 2 Diabetes
The keto diet can help people with Type 2 diabetes lose weight and manage their blood sugar levels. A recently published randomized crossover trial comparing the effects of ketogenic and Mediterranean diets revealed that patients who adhered to a well-formulated ketogenic diet experienced improved glucose control and reduced body weight. A small study in women with type 2 diabetes also found that following a ketogenic diet for 90 days significantly reduced levels of hemoglobin A1C, which is a measure of long-term blood sugar management.
Reduction of Heart Disease Risk Factors
Research suggests that a ketogenic diet can reduce the risk of heart disease. A systematic review published in the American Journal of Clinical Nutrition in 2019 found that a ketogenic diet can lower markers of inflammation, which is associated with a decreased risk of heart disease. Furthermore, a study published in Circulation in 2020 demonstrated that a low-carbohydrate, high-fat ketogenic diet could reduce low-density lipoprotein (LDL) cholesterol levels, a significant risk factor for heart disease. The keto diet may lower your risk of developing cardiovascular disease by lowering your blood pressure, improving your HDL (“good”) cholesterol levels and lowering your triglycerides.
Neurological Benefits
Healthcare providers often put children with epilepsy on the keto diet to reduce or even prevent seizures by altering the “excitability” part of their brain. Research has shown the keto diet may help improve neurological conditions such as Alzheimer’s disease, autism and brain cancers such as glioblastoma. A ketogenic diet regulates brain metabolism, mitochondrial homeostasis, and inflammation in Alzheimer disease by increasing mitochondrial function and reducing oxidative stress.
Other Potential Benefits
The ketogenic diet may also offer benefits for:
- Nonalcoholic Fatty Liver Disease (NAFLD): The ketogenic diet induces a shift in the gut microbiome, resulting in increased folate production and reduced inflammation and oxidative stress.
- Polycystic Ovary Syndrome (PCOS): A crossover study compared the effects of a standard diet and a low-carbohydrate diet on PCOS and showed that the low-carbohydrate diet decreased glycemia, fasting serum insulin, and testosterone and increased insulin sensitivity.
- Cancer: The therapeutic impact of the ketogenic diet on tumors, such as neuroblastoma, acute myeloid leukemia, and glioblastoma, is attributed to its ability to downregulate GPR109A expression, activate mTORC1, and reduce glucose uptake at the tumor site.
Potential Risks and Side Effects
Despite the potential benefits, it's important to be aware of the possible risks and side effects associated with the ketogenic diet:
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The "Keto Flu"
The ketogenic diet may present some common and generally mild short-term adverse effects, known as the "keto flu." These symptoms can include nausea, vomiting, headache, fatigue, dizziness, insomnia, reduced exercise tolerance, and constipation. These symptoms resolve in a few days to weeks. Ensuring adequate fluid and electrolyte intake can help counter some of these symptoms. You may experience multiple days of headache, fatigue and constipation a few weeks into the keto diet, which can be attributed at least in part to the body losing water. But you might also experience brain fog, irritability or difficulty sleeping.
Nutrient Deficiencies
“Because the keto diet is so restricted, you’re not receiving the nutrients - vitamins, minerals, fibers - that you get from fresh fruits, legumes, vegetables and whole grains,” says Dr. Ring. In particular, low fiber intake can disrupt gut microbiota and lead to chronic constipation, while inadequate magnesium, vitamin C and potassium can contribute to muscle cramps, fatigue and weakened immune function.
Cardiovascular Concerns
The high-fat nature of the diet could also have negative impacts on heart health. The American Heart Association recommends limiting saturated fat intake to less than 6%. “In practice, many people eat high amounts of saturated fats, which could increase your risk of heart disease,” says Dr. Cheema. “You may be eating a lot of fatty meat thinking it’s a good thing for you because it's high in fat. This can dramatically alter your lipid profile. While high-fat diets can elevate LDL (“bad”) cholesterol, the type of saturated fat matters. The bottom line is that having more fats in your diet can lead to higher cholesterol.
Kidney Problems
The keto diet may not be appropriate for everyone, specifically people with kidney disease. “Although more research is needed in that area, there is some suggestion that it can make kidney disease worse over time,” says Dr. Some people also experience dehydration on the keto diet because they’re eliminating glycogen, which holds water, from the bloodstream.
Other Potential Side Effects
- Low Blood Pressure: The keto diet can cause your blood pressure to drop in the short term due to a reduction in blood volume and changes in your fluid balance.
- Low Blood Sugar: Following a keto diet can also cause your blood sugar to drop, which can be dangerous for people living with diabetes.
- Social Isolation and Disordered Eating: Strict diets like keto could also cause social isolation or disordered eating.
Who Should Avoid the Ketogenic Diet?
The ketogenic diet is contraindicated in individuals with pancreatitis, liver failure, disorders of fat metabolism, primary carnitine deficiency, carnitine palmitoyltransferase deficiency, carnitine translocase deficiency, porphyrias, or pyruvate kinase deficiency. Additionally, individuals following a ketogenic diet may rarely experience a false positive breath alcohol test due to the conversion of acetone to isopropanol by hepatic alcohol dehydrogenase, resulting in an inaccurate reading.
Important Considerations Before Starting a Keto Diet
As with any drastic diet change, you’ll want to consult your primary care physician before you begin. Sullivan suggests meeting with a dietitian to understand how much fat intake is needed and what kinds of fats should be consumed. “On keto, we are increasing the amount of fat in someone’s diet, but we need to make sure it’s a healthier type of fat.”