The hyperketosis diet, often referred to as the ketogenic or "keto" diet, is a dietary approach characterized by a high intake of fats, moderate protein consumption, and a very low intake of carbohydrates. This dietary plan has garnered significant attention as a potential weight-loss strategy, tracing its roots back to the low-carb diet craze that began in the 1970s with the Atkins diet.
Historical Context and Evolution
The ketogenic diet has a rich history, with its use dating back centuries for the treatment of specific medical conditions. In the 19th century, it was commonly employed to assist in managing diabetes. By 1920, the diet was introduced as an effective treatment for epilepsy in children for whom medication proved ineffective. The commercial success of the Atkins diet popularized low-carb diets, paving the way for other variations like the Paleo, South Beach, and Dukan diets, all of which are high in protein but moderate in fat.
Understanding Ketosis
The central premise of the ketogenic diet for weight loss lies in the deprivation of glucose, the body's primary energy source derived from carbohydrate consumption. In the absence of sufficient glucose, the body turns to an alternative fuel source called ketones, produced from stored fat. This process is termed "keto"-genic.
The brain, which requires a steady supply of approximately 120 grams of glucose daily, cannot store glucose itself. During periods of fasting or minimal carbohydrate intake, the body initially draws upon stored glucose from the liver and temporarily breaks down muscle to release glucose. If this condition persists for 3-4 days, leading to the depletion of stored glucose, insulin levels decrease, and the body begins to utilize fat as its primary fuel.
The liver then produces ketone bodies from fat, which can be used in the absence of glucose. The accumulation of ketone bodies in the blood results in a state called ketosis. Healthy individuals naturally experience mild ketosis during fasting periods (such as overnight) and strenuous exercise. Proponents of the ketogenic diet assert that with careful adherence, blood ketone levels should not reach harmful levels, known as "ketoacidosis," as the brain utilizes ketones for fuel, and healthy individuals typically produce sufficient insulin to prevent excessive ketone formation.
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The rate at which ketosis occurs and the quantity of ketone bodies that accumulate in the blood vary among individuals, influenced by factors such as body fat percentage and resting metabolic rate.
Ketoacidosis: Understanding the Risks
Excessive ketone bodies can lead to a dangerously toxic level of acid in the blood, a condition known as ketoacidosis. During ketoacidosis, the kidneys begin to excrete ketone bodies along with body water in the urine, resulting in some fluid-related weight loss. Ketoacidosis primarily occurs in individuals with type 1 diabetes, as they do not produce insulin, a hormone that prevents the overproduction of ketones. However, in rare instances, ketoacidosis has been reported in non-diabetic individuals following a prolonged, very low carbohydrate diet.
Macronutrient Ratios and Dietary Guidelines
There is no one "standard" ketogenic diet with a specific ratio of macronutrients (carbohydrates, protein, fat). However, the ketogenic diet typically reduces total carbohydrate intake to less than 50 grams a day, which is less than the amount found in a medium plain bagel, and can be as low as 20 grams a day. Popular ketogenic resources generally suggest an average of 70-80% fat from total daily calories, 5-10% carbohydrate, and 10-20% protein. For a 2000-calorie diet, this translates to approximately 165 grams of fat, 40 grams of carbohydrate, and 75 grams of protein.
The protein amount on the ketogenic diet is kept moderate compared to other low-carb, high-protein diets, as excessive protein consumption can hinder ketosis.
Food Choices on a Ketogenic Diet
Many versions of ketogenic diets exist, but all restrict carb-rich foods. Obvious examples include starches from both refined and whole grains like breads, cereals, pasta, rice, and cookies; potatoes, corn, and other starchy vegetables; and fruit juices. Less obvious restrictions include beans, legumes, and most fruits.
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Most ketogenic plans permit foods high in saturated fat, such as fatty cuts of meat, processed meats, lard, and butter, as well as sources of unsaturated fats like nuts, seeds, avocados, plant oils, and oily fish. Strong emphasis is placed on fats at each meal and snack to meet the high-fat requirement.
Some dairy foods may be allowed, although those high in natural lactose sugar, such as cream, ice cream, and full-fat milk, are restricted. Protein intake remains moderate, and certain fruits in small portions, like berries, are permitted. Other fruits are restricted unless factored into designated carbohydrate limits.
"Net Carbs" and "Impact Carbs": Deciphering Food Labels
"Net carbs" and "impact carbs" are terms commonly encountered in ketogenic and diabetic diets. These unregulated, interchangeable terms are used by food manufacturers as a marketing strategy, appearing on some food labels to suggest that the product contains less "usable" carbohydrate than listed. Net carbs or impact carbs refer to the amount of carbohydrate directly absorbed by the body and contributing calories. They are calculated by subtracting the amount of indigestible carbohydrates from the total carbohydrate amount. Indigestible (unabsorbed) carbohydrates include insoluble fibers from whole grains, fruits, and vegetables, as well as sugar alcohols like mannitol, sorbitol, and xylitol, commonly used in sugar-free diabetic food products.
However, these calculations are not precise or reliable, as the effect of sugar alcohols on absorption and blood sugar can vary. Some sugar alcohols may still contribute calories and raise blood sugar. The total calorie level remains unchanged despite the amount of net carbs, an important factor in weight loss.
Potential Benefits of the Ketogenic Diet
Programs often suggest following a ketogenic diet until the desired amount of weight is lost. The ketogenic diet has demonstrated beneficial metabolic changes in the short term. Along with weight loss, health parameters associated with carrying excess weight have improved, including insulin resistance, high blood pressure, and elevated cholesterol and triglycerides. There is also growing interest in the use of low-carbohydrate diets, including the ketogenic diet, for type 2 diabetes.
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Research findings specific to the ketogenic diet (containing about 70-80% fat, 10-20% protein, and 5-10% carbohydrate) have shown promising results. Diets termed "low carbohydrate" but not adhering to these specific ratios, allowing higher amounts of protein or carbohydrate, were excluded from consideration.
A meta-analysis of 13 randomized controlled trials following overweight and obese participants for 1-2 years on either low-fat diets or very-low-carbohydrate ketogenic diets found that the ketogenic diet produced a small but significantly greater reduction in weight, triglycerides, and blood pressure, and a greater increase in HDL and LDL cholesterol compared with the low-fat diet at one year.
A systematic review of 26 short-term intervention trials (varying from 4-12 weeks) evaluated the appetites of overweight and obese individuals on either a very low calorie (approximately 800 calories daily) or ketogenic diet (no calorie restriction but ≤50 gm carbohydrate daily) using a standardized and validated appetite scale. None of the studies compared the two diets with each other; rather, the participants’ appetites were compared at baseline before starting the diet and at the end. Despite losing a significant amount of weight on both diets, participants reported less hunger and a reduced desire to eat compared with baseline measures. The authors noted the lack of increased hunger despite extreme restrictions of both diets, which they theorized were due to changes in appetite hormones such as ghrelin and leptin, ketone bodies, and increased fat and protein intakes. The authors suggested further studies exploring a threshold of ketone levels needed to suppress appetite; in other words, can a higher amount of carbohydrate be eaten with a milder level of ketosis that might still produce a satiating effect? This could allow inclusion of healthful higher carbohydrate foods like whole grains, legumes, and fruit.
A study of 39 obese adults placed on a ketogenic very low-calorie diet for 8 weeks found a mean loss of 13% of their starting weight and significant reductions in fat mass, insulin levels, blood pressure, and waist and hip circumferences. Their levels of ghrelin did not increase while they were in ketosis, which contributed to a decreased appetite. However during the 2-week period when they came off the diet, ghrelin levels and urges to eat significantly increased.
A study of 89 obese adults who were placed on a two-phase diet regimen (6 months of a very-low-carbohydrate ketogenic diet and 6 months of a reintroduction phase on a normal calorie Mediterranean diet) showed a significant mean 10% weight loss with no weight regain at one year. The ketogenic diet provided about 980 calories with 12% carbohydrate, 36% protein, and 52% fat, while the Mediterranean diet provided about 1800 calories with 58% carbohydrate, 15% protein, and 27% fat. Eighty-eight percent of the participants were compliant with the entire regimen.
Potential Risks and Considerations
Following a very high-fat diet may be challenging to maintain. Some negative side effects of a long-term ketogenic diet have been suggested, including increased risk of kidney stones and osteoporosis, and increased blood levels of uric acid (a risk factor for gout). Possible nutrient deficiencies may arise if a variety of recommended foods on the ketogenic diet are not included. It is important to not solely focus on eating high-fat foods, but to include a daily variety of the allowed meats, fish, vegetables, fruits, nuts, and seeds to ensure adequate intakes of fiber, B vitamins, and minerals (iron, magnesium, zinc)-nutrients typically found in foods like whole grains that are restricted from the diet.
Furthermore, questions remain regarding the diet's health benefits for higher-risk individuals with multiple health conditions and the elderly. As fat is the primary energy source, there are concerns about the long-term impact on health from consuming different types of fats (saturated vs. unsaturated).
Scientific Evidence and Research Limitations
Available research on the ketogenic diet for weight loss is still limited. Most of the studies so far have had a small number of participants, were short-term (12 weeks or less), and did not include control groups. A ketogenic diet has been shown to provide short-term benefits in some people including weight loss and improvements in total cholesterol, blood sugar, and blood pressure. However, these effects after one year when compared with the effects of conventional weight loss diets are not significantly different.
Eliminating several food groups and the potential for unpleasant symptoms may make compliance difficult. An emphasis on foods high in saturated fat also counters recommendations from the Dietary Guidelines for Americans and the American Heart Association and may have adverse effects on blood LDL cholesterol.
Consulting Healthcare Professionals
A ketogenic diet may be an option for some people who have had difficulty losing weight with other methods. The exact ratio of fat, carbohydrate, and protein that is needed to achieve health benefits will vary among individuals due to their genetic makeup and body composition. Therefore, if one chooses to start a ketogenic diet, it is recommended to consult with one’s physician and a dietitian to closely monitor any biochemical changes after starting the regimen, and to create a meal plan that is tailored to one’s existing health conditions and to prevent nutritional deficiencies or other health complications. A modified carbohydrate diet following the Healthy Eating Plate model may produce adequate health benefits and weight reduction in the general population.
Additional Considerations
Different Types of Ketogenic Diets
Ketogenic diets can be categorized into four different types:
- The "classic" ketogenic diet: This diet typically consists of a ratio of 4:1 or 3:1 grams of fat to combined grams of carbohydrates and protein. A 4:1 ratio would break down caloric intake to 90% from fat, 6% from protein, and 4% from carbohydrates. The difficulty with a classic ketogenic diet is palatability.
- Medium Chain Triglyceride Diet: This type of ketogenic diet allows the individual to increase the number of carbohydrates and proteins in the diet. An increase in carbohydrates and protein make the diet more palatable. However, to keep ketone levels elevated, fat intake should come from medium-chain triglycerides. Medium-chain triglycerides help with ketosis because they are more easily absorbed and converted to ketones than long-chain triglycerides.
- Modified Atkin’s Diet: The modified Atkin’s diet is different from a typical Atkin’s diet because it replaces some of the protein in Atkin’s diet with fat. The typical ratio of fat to protein and carbohydrates is 1:1.
- Low Glycemic Index Ketogenic Diet: The glycemic index measures the effect that different types of carbohydrate foods have on blood sugar. Simple carbohydrates like sugar are rapidly absorbed and therefore have a high glycemic index. Complex carbohydrates like whole grains are more slowly absorbed and therefore have a lower glycemic index.
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.
Contraindications
Patients with diabetes taking insulin or oral hypoglycemic agents may experience severe hypoglycemia if their medications are not appropriately adjusted before initiating a 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.
Vegetarian and Vegan Keto Diets
It may be challenging for vegetarians and vegans to follow a keto diet, as they may usually get many of their calories from carbohydrates. Even sources of nonanimal protein, such as lentils and beans, can be relatively high in carbs. In the standard keto diet, animal products tend to make up a large portion of meals because these foods are naturally high in fat, high in protein, and low in carbohydrates. Though challenging, it is possible to follow a vegetarian or vegan keto diet. Those who do not eat meat or fish can replace these products with high fat plant-based foods.
Supplements
While no supplements are required, some can be useful.
- MCT oil: Added to drinks or yogurt, MCT oil provides energy and helps increase ketone levels.
- Minerals: Added salt and other minerals can be important when starting out due to shifts in water and mineral balance.
- 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.
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