The ketogenic diet, commonly known as the keto diet, is a high-fat, low-carbohydrate eating plan primarily used for weight loss. It involves drastically reducing carbohydrate intake and replacing it with fat. Restricting carbs and increasing fat intake can lead to ketosis, a metabolic state in which your body relies primarily on fat for energy instead of carbs. This metabolic shift promises various health benefits, but also carries potential risks. Understanding these aspects is crucial for anyone considering or currently following a keto diet.
What is the Ketogenic Diet?
The ketogenic or keto diet is a dietary approach characterized by high-fat and low-carbohydrate intake, aiming to facilitate weight loss, enhance mental clarity, and boost energy levels. By significantly reducing carbohydrate consumption and increasing fat and protein intake, this diet induces a metabolic state called ketosis, where the body utilizes fat as its primary fuel source instead of carbohydrates. The primary goal of the ketogenic diet is to decrease overall body fat and improve metabolic health. Recent research indicates potential benefits in reducing the risk of certain diseases, including type 2 diabetes, hyperlipidemia, heart disease, and cancer.
The keto diet shares many similarities with the Atkins and low carb diets. Carb intake on the keto diet is typically limited to fewer than 50 grams per day, which can come as a shock to your body.
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.
- 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. The information in this article mostly applies to the standard ketogenic diet (SKD), although many of the same principles also apply to the other versions.
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The Science Behind Ketosis
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. Carbohydrates typically serve as the main source of energy production in the body's tissues. However, 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. Two prominent metabolic processes come into play when carbohydrates are limited in body tissues: gluconeogenesis and ketogenesis.
Gluconeogenesis is the process by which the body produces glucose internally, primarily in the liver, using substrates such as pyruvate, lactic acid, glycerol, and specific amino acids classified as glucogenic. When glucose availability drops, the endogenous breakdown of glucose cannot provide sufficient energy, ie, adenosine triphosphate (ATP). The metabolic pathway switches to ketogenesis to provide an alternate energy source in the form of ketone bodies. Ketone bodies replace glucose as a primary source of energy.
During ketogenesis, insulin secretion is low due to feedback from blood glucose levels, leading to a decrease in the stimulation of fat and glucose storage. Other hormonal changes may contribute to the increased fat breakdown resulting in fatty acids. Fatty acids are metabolized to acetoacetate, later converted to beta-hydroxybutyrate and acetone. These primary 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. 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.
Ketone bodies synthesized within the body can be effectively utilized as an energy source by vital organs such as the heart, muscle tissue, and kidneys. 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.
Ketone body production depends on several factors, such as resting basal metabolic rate (BMR), body mass index (BMI), and body fat percentage. Ketone bodies, often referred to as a "super fuel," produce a greater amount of ATP than glucose. When comparing energy production, 100 grams of acetoacetate generates 9,400 grams of ATP, 100 grams of beta-hydroxybutyrate yields 10,500 grams of ATP, while 100 grams of glucose produces only 8,700 grams of ATP. Ketone bodies enable the body to maintain efficient fuel production even when experiencing a caloric deficit. Four types of ketogenic diets are categorized based on the percentage of macronutrients they contain, allowing for increased compliance with the regimens. The ketogenic diet's short-term effects (up to 2 years) are well-reported and established. However, the long-term health implications are unknown due to limited literature.
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Potential Benefits of the Keto Diet
The ketogenic diet is a popular diet for weight loss and general health. The ketogenic diet (or keto diet, for short) is a low carb, high fat diet that offers many health benefits. In fact, many studies show that this type of diet can help you lose weight and improve your health. Ketogenic diets may even have benefits against diabetes, cancer, epilepsy, and Alzheimer’s disease.
Weight Loss
A ketogenic diet is an effective way to lose weight and lower risk factors for disease. Research shows that the ketogenic diet may be as effective for weight loss as a low fat diet. What’s more, the diet is so filling that you can lose weight without counting calories or tracking your food intake.
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.
Management of Diabetes
Diabetes is characterized by changes in metabolism, high blood sugar, and impaired insulin function. One older study found that the ketogenic diet improved insulin sensitivity by a whopping 75%. 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.
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. This is an important benefit when considering the link between weight and type 2 diabetes. 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.
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Other Health Conditions
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.
- Epilepsy. Research has shown that the ketogenic diet can cause significant reductions in seizures in epileptic children. The ketogenic diet, described initially as a successful treatment for epilepsy, has regained attention through numerous studies showcasing its effectiveness in patients with drug-resistant epilepsy and certain pediatric epilepsy syndromes.
- 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.
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. This results in suppressed tumor growth, improved survival rates, and enhanced efficacy of chemotherapy.
Risks and Side Effects
While the keto diet offers several potential benefits, it also carries risks and potential side effects that individuals should be aware of.
The "Keto Flu"
The ketogenic diet may present some common and generally mild short-term adverse effects, known as the "keto flu." As your body depletes its carb stores and switches to using ketones and fat for fuel at the start of this eating pattern, you may experience flu-like symptoms. These include headaches, dizziness, fatigue, nausea, and constipation - due in part to dehydration and electrolyte imbalances that happen as your body adjusts to ketosis.
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.
Kidney Stones and Chronic Kidney Disease
High fat animal foods, such as eggs, meat, and cheese, are staples of the keto diet because they don’t contain carbs. If you eat a lot of these foods, you may have a higher risk of kidney stones. That’s because a high intake of animal foods can cause your blood and urine to become more acidic, leading to increased excretion of calcium in your urine. Some studies also suggest that the keto diet reduces the amount of citrate that’s released in your urine. Given that citrate can bind to calcium and prevent the formation of kidney stones, reduced levels of it may also raise your risk of developing them.
Additionally, people with chronic kidney disease (CKD) should avoid keto, as weakened kidneys may be unable to remove the acid buildup in your blood that results from these animal foods. This can lead to a state of acidosis, which can worsen the progression of CKD. What’s more, lower protein diets are often recommended for individuals with CKD, while the keto diet is moderate to high in protein.
Constipation and Gut Health
Since the keto diet restricts carbs, it can be difficult to meet your daily fiber needs. Some of the richest sources of fiber, such as high carb fruits, starchy vegetables, whole grains, and beans, are eliminated on the diet because they provide too many carbs. As a result, the keto diet can lead to digestive discomfort and constipation. A 10-year study in children with epilepsy on the ketogenic diet found that 65% reported constipation as a common side effect.
What’s more, fiber feeds the beneficial bacteria in your gut. Having a healthy gut may help boost immunity, improve mental health, and decrease inflammation. A low carb diet that’s lacking in fiber, such as keto, may negatively affect your gut bacteria - although current research on this topic is mixed. Some keto-friendly foods that are high in fiber include flax seeds, chia seeds, coconut, broccoli, cauliflower, and leafy greens.
Nutrient Deficiencies
Since the keto diet restricts several foods, especially nutrient-dense fruits, whole grains, and legumes, it may fail to provide recommended amounts of vitamins and minerals. In particular, some studies suggest that the keto diet doesn’t provide enough calcium, vitamin D, magnesium, and phosphorus. A study that evaluated the nutrient composition of common diets revealed that very low carb eating patterns like Atkins, which is similar to keto, provided sufficient amounts for only 12 of the 27 vitamins and minerals your body needs to obtain from food.
Notably, guidelines for clinicians who manage people on a very low calorie keto diet for weight loss recommend supplementing with potassium, sodium, magnesium, calcium, omega-3 fatty acids, psyllium fiber, and vitamins B, C, and E. Keep in mind that the nutritional adequacy of this diet depends on the specific foods that you eat. A diet rich in healthy low carb foods, such as avocados, nuts, and non-starchy vegetables, provides more nutrients than processed meats and keto treats.
Hypoglycemia in Type 1 Diabetics
Low carb diets like keto have been shown to help manage blood sugar levels in people with diabetes. In particular, some studies suggest that keto may help decrease levels of hemoglobin A1c, a measure of average blood sugar levels.
However, individuals with type 1 diabetes may be at a high risk of more episodes of low blood sugar (hypoglycemia), which is marked by confusion, shakiness, fatigue, and sweating. Hypoglycemia can lead to coma and death if not treated. A study in 11 adults with type 1 diabetes who followed a ketogenic diet for over 2 years found that the median number of low blood sugar events was close to 1 per day. Individuals with type 1 diabetes typically experience low blood sugar if they are taking too much insulin and not consuming enough carbs. Continuing Education Activity
Other Potential Long-Term 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
Supplements for the Keto Diet
If a person eats a variety of healthful whole foods on the keto diet, they may find that they have very few, if any, nutritional deficiencies. However, some supplements can help with the discomfort that can occur as a person’s body adjusts to a keto diet. They can also help a person get the right amount of fats in their diet. Adjusting to extreme carbohydrate restriction can cause uncomfortable side effects because the body takes time to get used to making ketones and using this new source of energy. Certain supplements, such as electrolytes, digestive enzymes, and L-theanine, may help minimize these symptoms.
MCT Oil
Medium chain triglyceride oil, or MCT oil, is a type of fatty acid that occurs in coconut oil. The liver metabolizes these fats, transforming them into a source of fuel. A 2018 study found a “clear ketogenic effect” when people took supplemental MCTs. MCTs may also help a person lose more weight, according to some research. MCTs are not in many other foods, so taking a supplement can allow a person to get the potential benefits of these fats. MCT oil is liquid at room temperature. People can mix it into foods or smoothies, or they can take it alone. A standard dose is 1 teaspoon. Added to drinks or yogurt, MCT oil provides energy and helps increase ketone levels.
Magnesium
The body needs magnesium for many different processes, including food metabolism, transmission of nerve signals, balance of fluids, maintenance of bone and muscle health, and more. Although a few keto friendly foods, such as nuts and spinach, are high in magnesium, the diet is low in other magnesium rich foods, including whole grains, fruit, beans, and dairy products. If a person is not getting adequate magnesium from foods while following the keto diet, they may need a supplement. A supplement may also be beneficial for those experiencing constipation.
Some evidence suggests that many people are at a high risk of magnesium deficiency due to chronic diseases, medications, and decreases in food crop magnesium levels. Magnesium supplements are available in different forms. The Office of Dietary Supplements (ODS) state that the body may absorb some types - including magnesium aspartate, citrate, lactate, glycinate, and chloride forms - more readily than others. However, a doctor may recommend a specific form of magnesium to meet a person’s needs. High doses of magnesium can cause diarrhea. Therefore, a person should start with the lowest dose on the package, which may be 100-200 milligrams (mg) per day. If no diarrhea occurs, a person may gradually increase the dose, although they should not take more than 400 mg per day unless a doctor advises a higher dose.
Electrolytes
As the body adjusts to a keto diet, the kidneys may excrete more water. This increased excretion can cause the body to lose vital electrolytes, which include not only magnesium but also potassium, chloride, phosphorus, and sodium. Taking an electrolyte supplement can help rebalance the levels of these minerals. Electrolyte supplements vary in their mineral content, so it is important for a person to read labels to be sure that they are not getting too much of these minerals. Most contain a combination of calcium, potassium, and magnesium. A keto friendly supplement should contain no sugar or sweeteners. Alternatively, a person may wish to try adopting the following practices to get the three main electrolytes:
- taking a magnesium supplement daily
- adding some extra salt to the diet or consuming beef or chicken broth daily
- eating potassium rich, keto friendly foods, such as avocado or cooked spinach, every day
Added salt and other minerals can be important when starting out due to shifts in water and mineral balance.
Fiber
Fiber is the indigestible part of plant foods, and it is important for keeping the digestive system healthy. Without enough fiber, a person may become constipated. People should get 25-31 grams of fiber per day, depending on their age and sex. Many keto friendly foods, including nuts, seeds, avocado, and leafy greens, contain fiber. However, if a person focuses on meat, seafood, eggs, and dairy, they may not get enough fiber on the keto diet. Fiber supplements can be helpful if people find that they become constipated while following the keto diet. They should look for a keto friendly formula that does not contain sugar. It is also important to drink plenty of water, which helps keep digestion running smoothly. Taking fiber supplements without adequate water intake could make constipation worse.
Omega-3 Fatty Acids
Omega-3 fats are a type of polyunsaturated fatty acid (PUFA). Omega-3s are present in high amounts in some fatty fish and eggs, and they also occur in plant form in some nuts and seeds. Studies show that consuming enough omega-3s can have health benefits, including helping prevent weight gain. The ODS state that many people could benefit from a higher intake of omega-3s. The other type of PUFA, omega-6, occurs in many conventionally raised, grain-fed meats. Omega-6s are also in some vegetable oils, including corn and cottonseed oil.
One study found that among people following a ketogenic Mediterranean diet, those who ate more omega-3s experienced positive effects on their insulin, triglyceride, and inflammation levels. Omega-3 levels may be higher in meats that come from grass-fed or pasture raised animals, as well as in eggs from pasture raised or vegetarian-fed hens. If a person on the keto diet does not eat grass-fed meats or seafood, they may want to consider an omega-3 supplement. Omega-3 supplements vary in their dosage and origin. Some come from fish oil, krill oil, algae, flaxseed, or other natural omega-3 sources. A person should follow the dosage directions on the product. People who take medications that affect blood clotting, such as blood thinners, should ask a doctor before using omega-3 supplements. People who are allergic to fish or shellfish should avoid supplements that contain fish oil, krill oil, or other fish based ingredients.
Digestive Enzymes
The gut uses enzymes to break down different parts of foods during digestion. If a person who is switching to a keto diet ate a large number of carbs previously, they might find that they have trouble with the change. Symptoms such as bloating, nausea, fatigue, and constipation are common because of the high amount of fats that a keto diet requires. Digestive enzymes could help alleviate some of these symptoms. Many of these supplements contain several different types of enzyme, but it is important to choose one that contains lipase, which is the enzyme that breaks down fat. Supplements that contain proteases and peptidases are also a good choice, as these break down protein. In most cases, a person will take their digestive enzymes with a high fat meal or a few minutes before eating. They should always follow the dosage directions on the product and look for those that are keto friendly.
L-Theanine
L-theanine is an amino acid that is difficult to obtain from foods. The only known good source of l-theanine is green or black tea, but the amounts may vary depending on the type of tea and how a person brews it. Studies show that taking this supplement may help improve sleep quality, decrease anxiety, and improve mental cognition. As a result, it could be an excellent option if a person experiences mental fog or trouble concentrating as they transition to the keto diet. L-theanine supplements are available in pill or powder form. There is no recommended dosage, but many products suggest 100-400 mg daily. Alternatively, people may choose to drink unsweetened tea, particularly green tea, which contains natural L-theanine.
Other Supplements
- Caffeine. Caffeine can have benefits for energy, fat loss, and performance.
- Exogenous ketones. This supplement may help raise the body’s ketone levels.
- Creatine. Creatine provides numerous benefits for health and performance. This can help if you are combining a ketogenic diet with exercise.
- Whey. Use half a scoop of whey protein in shakes or yogurt to increase your daily protein intake.
Keto-Friendly Foods
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
It’s best to base your diet mostly on whole, single-ingredient foods.
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.