In a world saturated with weight-loss strategies and diet plans, the ketogenic, or "keto," diet stands out as a time-tested, low-carbohydrate, high-fat eating regimen. Initially employed in the 19th century for diabetes management and later as a treatment for epilepsy in children during the 1920s, the keto diet has recently surged in popularity as a potential weight-loss method. This resurgence is largely attributed to the low-carb diet trend that gained momentum in the 1970s with the introduction of the Atkins diet.
Understanding the Ketogenic Diet
The fundamental principle behind the ketogenic diet for weight loss lies in depriving the body of glucose, its primary energy source derived from carbohydrate consumption. This deprivation triggers the production of an alternative fuel called ketones, which are derived from stored fat. The brain, which requires a steady supply of approximately 120 grams of glucose daily, cannot store it. Therefore, during periods of fasting or when carbohydrate intake is minimal, the body initially utilizes stored glucose from the liver and temporarily breaks down muscle to release glucose.
If this process continues for three to four days, and the body's stored glucose becomes depleted, insulin levels decrease, and the body begins to rely on fat as its primary fuel source. 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 sleep, and during strenuous exercise.
Proponents of the ketogenic diet assert that, when followed carefully, blood ketone levels should remain within a safe range. This is because the brain utilizes ketones for fuel, and healthy individuals typically produce sufficient insulin to prevent excessive ketone formation. However, the rate at which ketosis occurs and the concentration of ketone bodies in the blood can vary depending on individual factors such as body fat percentage and resting metabolic rate.
Ketoacidosis: A Potential Risk
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 fluid-related weight loss. Ketoacidosis primarily affects individuals with type 1 diabetes, as they do not produce insulin, the hormone responsible for preventing ketone overproduction. However, in rare instances, ketoacidosis has been reported in non-diabetic individuals following prolonged very low-carbohydrate diets.
Read also: Comprehensive Guide: Figure Competition Diet
Macronutrient Ratios in the Ketogenic Diet
There is no universally accepted "standard" ketogenic diet with a fixed ratio of macronutrients (carbohydrates, protein, and fat). However, the ketogenic diet typically restricts total carbohydrate intake to less than 50 grams per day, which is less than the amount found in a medium plain bagel, and can be as low as 20 grams per day. A common recommendation for ketogenic diets is an average of 70-80% of total daily calories from fat, 5-10% from carbohydrate, and 10-20% from 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 content of the ketogenic diet is kept moderate compared to other low-carb, high-protein diets, as excessive protein consumption can hinder ketosis.
Food Restrictions and Recommendations
Many variations of ketogenic diets exist, but all involve restricting carbohydrate-rich foods. Obvious examples include starches from refined and whole grains like breads, cereals, pasta, rice, and cookies, as well as potatoes, corn, and other starchy vegetables, and fruit juices. Less obvious examples include beans, legumes, and most fruits.
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, such as nuts, seeds, avocados, plant oils, and oily fish. Emphasis is placed on consuming fats at each meal and snack to meet the high-fat requirement. Some dairy foods may be allowed, but those high in natural lactose sugar, such as cream, ice cream, and full-fat milk, are typically restricted. Protein intake remains moderate, and certain fruits in small portions, such as berries, may be allowed.
"Net Carbs" and "Impact Carbs": Understanding 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 to suggest that a product contains fewer "usable" carbohydrates than listed. Net carbs or impact carbs represent 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 carbohydrates include insoluble fibers from whole grains, fruits, and vegetables, as well as sugar alcohols like mannitol, sorbitol, and xylitol, which are commonly used in sugar-free diabetic food products.
However, it is important to note that these calculations are not entirely accurate 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 levels. Additionally, the total calorie level remains unchanged despite the amount of net carbs, which is an important consideration for weight loss.
Read also: Fueling Figure Skating Performance
Benefits and Risks of the Ketogenic Diet
Ketogenic diets have been shown to produce beneficial metabolic changes in the short term. In addition to weight loss, improvements in health parameters associated with excess weight, such as insulin resistance, high blood pressure, and elevated cholesterol and triglycerides, have been observed. There is also growing interest in the use of low-carbohydrate diets, including the ketogenic diet, for managing type 2 diabetes.
However, it's important to note that research findings have been limited to studies specifically examining ketogenic diets with a macronutrient ratio of approximately 70-80% fat, 10-20% protein, and 5-10% carbohydrate. Diets described as "low carbohydrate" but not adhering to these specific ratios may allow for higher amounts of protein or carbohydrate.
Research on Ketogenic Diets for Weight Loss
A meta-analysis of 13 randomized controlled trials involving overweight and obese participants who followed either low-fat diets or very-low-carbohydrate ketogenic diets for 1-2 years found that the ketogenic diet resulted in a slightly greater reduction in weight, triglycerides, and blood pressure, and a greater increase in HDL and LDL cholesterol compared to the low-fat diet at one year.
A systematic review of 26 short-term intervention trials (ranging from 4-12 weeks) assessed the appetites of overweight and obese individuals on either a very low-calorie diet (~800 calories daily) or a ketogenic diet (no calorie restriction but ≤50 grams of carbohydrate daily) using a standardized and validated appetite scale. Although participants lost a significant amount of weight on both diets, they reported less hunger and a reduced desire to eat compared to baseline measures. The authors suggested that these changes in appetite may be due to alterations in appetite hormones such as ghrelin and leptin, ketone bodies, and increased fat and protein intakes.
A study of 39 obese adults placed on a ketogenic very low-calorie diet for 8 weeks showed 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 ghrelin levels 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.
Read also: Diet Plan: No Sugar, Carbs, Dairy
A study of 89 obese adults who followed 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 Side Effects
Maintaining a very high-fat diet can be challenging in the long term. Some potential negative side effects of a long-term ketogenic diet include an increased risk of kidney stones and osteoporosis, and increased blood levels of uric acid (a risk factor for gout). Nutrient deficiencies may also arise if a variety of recommended foods on the ketogenic diet are not included. It is crucial to consume a daily variety of 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 long-term health impacts of consuming different types of fats (saturated vs. unsaturated) as the primary energy source, and whether the diet's health benefits extend to higher-risk individuals with multiple health conditions and the elderly.
Limitations of Current Research
Available research on the ketogenic diet for weight loss is still limited. Most studies have involved a small number of participants, were short-term (12 weeks or less), and did not include control groups. While ketogenic diets have shown short-term benefits in some people, including weight loss and improvements in total cholesterol, blood sugar, and blood pressure, these effects are not significantly different from those of conventional weight loss diets after one year.
Eliminating several food groups and the potential for unpleasant symptoms may make compliance difficult. An emphasis on foods high in saturated fat also contradicts recommendations from the Dietary Guidelines for Americans and the American Heart Association and may have adverse effects on blood LDL cholesterol.
Who Should Consider a Ketogenic Diet?
A ketogenic diet may be an option for individuals who have struggled to lose weight with other methods. The precise ratio of fat, carbohydrate, and protein required to achieve health benefits will vary among individuals based on their genetic makeup and body composition. Therefore, if you choose to embark on a ketogenic diet, it is recommended to consult with your physician and a registered dietitian to closely monitor any biochemical changes after starting the regimen and to create a meal plan that is tailored to your 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 for the general population.
Calculating Net Carbs: A Detailed Guide
For individuals following the keto diet, it is essential to understand how to calculate "net carbs" in foods. Net carbs represent the amount of carbohydrate that is directly absorbed by the body and contributes calories. To calculate the number of net carbs in a serving, subtract the amount of fiber from the total number of carbs. If the food is processed, also subtract half the sugar alcohol content. These quantities are typically available on food labels.
Understanding the Components of Carbohydrates
- Total Carbs: This includes all the carbs in a serving of food, including those that the body cannot completely digest and transfer into glucose for energy.
- Net Carbs: These are the carbs that the body can absorb, also known as digestible carbs.
- Fiber: A type of carbohydrate that the body cannot digest and therefore cannot transform into glucose for energy.
- Sugar Alcohol: To calculate net carbohydrates in processed foods, subtract half the amount of sugar alcohol from the total number of carbs.
How Net Carbs Work in the Body
When a person consumes carbohydrates, the body turns those carbs into sugar, which cells use for energy. Significantly limiting carb intake causes the body to burn fat instead of carbs for energy, causing glucose levels to drop. This forces the body to produce ketones, acids that appear in the blood and urine when the body burns fat. When the body uses fat as energy and releases ketones, this is called ketosis. During ketosis, the body also produces less insulin and stores less fat as a result.
Net Carbs in Various Foods
- Fresh Meat and Fish: These foods generally contain no carbohydrates and are good sources of nutrients. Examples include turkey, pork, chicken, lamb, beef, veal, venison, shellfish, tuna, cod, salmon, and sardines.
- Dairy: Cheese tends to be low in carbs but high in fat, making it a good choice for keto diets. For example, 100 g of cheddar cheese has 2.44 g of carbs and 34 g of fat.
- Vegetables: It is important to research the carb content of vegetables, as some are higher in carbs than others.
- Fruits: Some fruits are high in carbs, so researching and checking labels is essential.
- Nuts and Seeds: These can be a good source of healthy fats and protein, but it is important to be mindful of their carb content.
- Wheat-Based Products: Rice, pasta, and cereals are high in carbs and should be limited on a keto diet.
Tips for Maintaining a Sustainable Keto Diet
- Gradual Changes: Ease into the diet gradually by eliminating one type of food at a time.
- Whole, Unprocessed Foods: Consume carbs from whole, unprocessed foods to benefit from their vitamins and minerals.
- Monitoring: Regular health monitoring is important to check for any effects on the heart, especially for people with diabetes.
Common Questions About Carb Intake and the Ketogenic Diet
- How many carbs can I eat and stay in ketosis? Generally, a person should consume up to 50 g of carbs per day to stay in ketosis, but this can vary slightly between individuals.
- Is 100 g carbs a day keto? The ketogenic diet typically reduces net carbohydrate intake to roughly 50 g a day. Other low-carb diets may allow up to 130 g of carbs per day.
- Can you lose weight on 50 g carbs a day? Following a low-carbohydrate diet that involves consuming roughly 50 g of carbs a day, such as the keto diet, may help with weight loss.
- What does 50 g net carbs look like? Depending on the foods a person consumes, 50 g net carbs can vary. For example, with low carb foods, around 1,000 g of broccoli, raspberries, or Brazil nuts are roughly 50 g net carbs. However, with high carb foods, 200 g of cashews or 100 g of lentils are about 50 g net carbs.
Net Carbs vs. Total Carbs: What's the Difference?
Carbohydrates are sugars in food that supply energy in the form of calories. Net carbs represent the number of carbohydrates that are actually absorbed by your body without impacting blood sugar levels and insulin response. Low-carb diets have been shown to be a successful approach to helping people lose weight. A low-carb diet is generally considered eating less than 150 grams of carbs per day.
Calculating Net Carbs: A Step-by-Step Guide
- Read the nutrition label and determine the grams of total carbs, the grams of fiber, and the sugar alcohols.
- To calculate the net carbohydrates, take the total carbohydrates and subtract both the grams of fiber and the sugar alcohols.
The Benefits of Fiber
Fiber provides a slew of benefits, and the USDA recommends at least 25-30 grams of fiber for every 2000 calories you eat. Higher-fiber foods can also help you to feel full, which can help with overall lower calorie intake and weight loss.
Using a Keto Calculator
A keto calculator can help you determine your ideal macronutrient ratios for weight loss or maintenance. It takes into account factors such as your activity level, body fat percentage, and goals.