The newest buzzword to hit the diet world seems to be keto — which refers to the high-fat, low-carb ketogenic diet. With claims that you can eat all the fat you want, never feel hungry again,?lower your blood sugar?if you have?type 2 diabetes, and even boost your athletic performance, the diet promises something for everyone.
But what exactly is the ketogenic diet, and is the weight loss program right for you? Let’s take a closer look before you attempt to make over your eating habits and lifestyle.
What Is the Ketogenic Diet Exactly?
The ketogenic diet is based on the principle that by depleting the body of?carbohydrates, which are its primary source of energy, you can force the body to burn fat for fuel, thereby maximizing weight loss. When you consume foods that contain carbohydrates, the body converts those carbohydrates into glucose, or blood sugar, which it then uses for energy. (1)
Because glucose is the simplest form of energy for the body to use, it’s always used for energy before your body turns to stored fat for fuel. (1)
On a ketogenic diet, the goal is to?restrict carbohydrate intake?so that the body must break down fat for energy. When this occurs, fat is broken down in the liver, thereby producing ketones, which are by-products of your metabolism. These ketones are then used to fuel the body in the absence of glucose. (2)
How Do You Follow the Ketogenic?Diet?
There are several types of the keto?diet, but essentially, to achieve a state of ketosis, you have to severely reduce the amount of carbs you eat. (You can use this ketogenic?calculator to create a custom food plan.) Data suggest the average American man over age 20 consumes 47.4 percent of his daily calories from carbs, and the average American woman over age 20 consumes 49.6 percent of her daily calories from carbs. (3) But in the classic ketogenic diet, which was originally used for the management of seizure disorders, 80 to 90 percent of calories come?from fat, 5 to 15 percent come from protein, and 5 to 10 percent come from carbohydrates.
A modified version of the ketogenic diet, which allows you to eat protein more liberally — at 20 to 30 percent of your total calories — with the same carbohydrate restriction, is the more commonly used version of the diet today. Some of the aims of the latest version of the ketogenic diet are?weight loss, weight management, and improved athletic performance.
An In-Depth Look at Ketosis: The Fat-Burning Mechanism That Makes the Keto Diet Work
The ketogenic diet for weight loss is based on the idea that driving the body into ketosis will maximize fat loss. Ketosis is a normal metabolic process that occurs when the body does not have enough?glucose?stores for energy. When these stores are depleted, the body resorts to burning stored fat for energy instead of carbs. ?This process produces acids called ketones, which build up in the body and can be used for energy. (2)RELATED: 21 Tips for Weight Loss That Actually Work
How Do You Know If You're in Ketosis?
To figure out whether you’re in a state of ketosis, check your urine for ketones. You can purchase ketone strips online or from a retail pharmacy. A strip that tests positive for ketones will indicate you have reached a state of ketosis. (2)
For people with diabetes, rapidly rising ketone levels can signal a health crisis that requires immediate medical attention. When there is an absence or not enough of the hormone insulin (or the body is too resistant to insulin to allow it to drive glucose into the cells for energy), the body cannot use glucose for fuel.?Insulin?helps ferry glucose to our cells and muscles for energy. Instead, in this case, the body resorts to burning stored fat for energy through the process of ketosis, leading to a buildup of ketones in the body.
As ketones accumulate in the bloodstream of a person with diabetes, they cause the blood to become more acidic, which can lead to the condition known as ketoacidosis. This condition can be potentially fatal and should be treated immediately.?(4)
What Are the Potential Health Risks and Benefits of the Keto Diet?
If you search online for the term “keto diet,” you'll see that the health claims associated with the ketogenic diet are numerous. But before you give this diet approach a try, it’s important to know what the science suggests about how it may affect your health. Namely, you'll want to be aware of potential keto?diet dangers.
Risk:?You May Suffer Fatigue and Other Symptoms As a Result of the Keto Flu
One of the most common side effects of starting the ketogenic diet is the “keto flu.” This term describes the often unpleasant, fatigue-inducing symptoms that occur as the body adjusts from a high-carbohydrate to a low-carbohydrate diet. During the keto flu, the body’s stored glucose begins depleting, and the body starts adapting to producing and utilizing ketones as energy. (2)
Symptoms of the keto flu include headache, fatigue, dizziness, sleep problems, heart palpitations, cramps, and diarrhea. These side effects usually lessen and eventually resolve in about two weeks. (2) But to lessen the effects of any discomfort, simply consider slowly transitioning onto a ketogenic diet rather than rushing to change your eating habits. By slowly lowering your carbohydrate intake, while gradually increasing your intake of dietary fat over time, you can transition with less of a negative impact and potentially prevent the keto flu.
Risk: You May Experience Constipation If You Don’t Eat Enough Fruits and Veggies
Risk: You Could Develop Potentially Dangerous Nutrient Deficiencies
Further, eliminating food groups can be problematic. “Ketogenic diets are often low in calcium, vitamin D, potassium, magnesium, and folic acid, which over time can lead to nutrient deficiencies if the diet is not planned carefully,” adds?Marie?Spano, RD,?CSCS, who is based in Atlanta.
Risk: You May Harm Your Heart Due to the Diet’s Focus on Animal Fat and Protein
Reliance on a diet rich in animal fats and proteins may also have a negative impact on heart health, research shows. (6) “This diet is not for anyone who is at risk of developing cardiovascular disease or who has already been diagnosed with it,” Spano cautions.
This means that if you have risk factors for heart disease — such as elevated?cholesterol levels, high blood pressure (hypertension), or a strong family history of the disease — you should use caution when following this diet. The diet's heavy reliance on fat, especially saturated fat, can elevate cholesterol levels, further increasing your chances of developing heart disease in the future. (7)RELATED: Is the Paleo Diet Good for Heart Health?
Risk: You May Experience Potentially Dangerous Low Blood Sugar If You Have Diabetes
For any individual with diabetes, discussing dietary changes — especially those as dramatic as the ones the?ketogenic diet requires — with your?healthcare team?is essential. Because carbohydrates are broken down into glucose in the blood, cutting carbohydrates from your diet could cause levels to crash rapidly depending on your current medication regimen. Such a change may require significant adjustments to medication and insulin to prevent dangerous side effects such as low blood sugar, called?hypoglycemia. (8)
Risk: You May Experience Weight Cycling, Negatively Affecting Your Metabolism
Outside of physical health changes, one of the biggest concerns of the ketogenic diet may be in long-term adherence. “It’s a very difficult diet to stick to and maintain. Compliance is a challenge because it is so restrictive,” explains Mohr.
Following a strict diet for weight loss and then quickly reverting to old habits when the dietary changes are too restrictive can lead to what is known as weight cycling, or yo-yo dieting. Gaining and losing the same weight over and over can start to have a negative impact on your self-image and motivation, and potentially your health. (9)
Benefit: You May See Improvements in Your Athletic Performance?
For athletes, research on the?keto?diet highlights potential improvements in athletic performance, especially when it comes to endurance activities. An article suggests?ketogenic-type diets may allow endurance athletes to rely mostly on stored fat for energy during exercise rather than having to refuel with simple carbohydrates during endurance training and competition while additionally improving recovery times. (10)
Benefit: You Could Lose Weight Fast — But Not Necessarily More Than You’d See From Other Diets
If you’re looking to lose weight, one benefit the?ketogenic?diet may offer is the ability to suppress appetite.?A review of this form of eating suggests it may help decrease appetite, but how this actually happens needs to be studied further. (11)
When it comes to weight loss — a big possible draw of the plan for many individuals — the benefits of the?ketogenic?diet may not be much different from any other diet plan. “There is no magical weight loss benefit that can be achieved from this diet,” says Spano. “The?ketogenic?diet may help weight loss in the same way other diets help — by restricting food choices so you eat?fewer calories.”
Mohr?agrees. “Cutting so many carbohydrates is a big reduction in calories,” he says, adding that this effect will lead to a loss of water weight up front, “which is why people like the immediate response of weight loss that comes from this type of diet.”RELATED: 10 Essential Facts About Metabolism and Weight Loss
Benefit: You May See Better Blood Glucose Control If You Have Type 2 Diabetes
For individuals with diabetes, adapting a very low-carbohydrate diet, such as the?ketogenic?diet, may offer some benefits when it comes to glucose management. For instance, a review found that dietary restriction of carbohydrate may reduce or eliminate the need for medication in individuals with type 2 diabetes. (12)
How Can Keto Help People With Type 2 Diabetes?
Because the main tenet of the keto?diet is counting and cutting carbs?— a commonly used way to control blood sugar — this eating approach has become increasingly popular among people with type 2 diabetes who are looking to?lower their A1C, which is the two- to three-month average measurement of blood sugar levels. Indeed, research suggests this diet may lead to fast weight loss and potentially lower blood sugar for people with the disease. (13)
But dietitians warn the keto?diet also comes with risks that are specific to people managing diabetes, including possible drug interactions and potentially dangerous low blood sugar if you're on medication, as well as kidney damage in people with dysfunctional kidneys due to the elevated level of ketones?in the blood. (14)
Plus, because keto?hasn't been studied long term, researchers don't know if the diet may also result in nutrient deficiencies regardless of whether you have diabetes.
If you're considering trying the keto?diet while managing diabetes, it's crucial to consult your diabetes-care team before doing so to make sure it's a safe and effective eating approach for you.
How to Get Started on the Ketogenic Diet
Here are some other things to know before you try this restrictive eating plan.
Can You Stick With the Carb?Restrictions?
Following a diet that drastically restricts carbohydrates requires carefully monitoring your food choices to ensure you are meeting your nutritional needs. Working together with a registered dietitian can make sure you follow this diet in a healthy manner without increasing your risk for complications or negative side effects. You can find a registered dietitian?at EatRight.org.
It’s important to remember that the goal of any dietary change is to promote a healthy lifestyle, so make sure to select a meal plan you can envision yourself following long term. If you know you will not be able to comply with such stringent carbohydrate restrictions for years to come, the ketogenic diet is most likely not the right choice for you.
What Are the Different Types of Keto?Diets?
There are various modifications of the ketogenic diet. The majority of individuals following a ketogenic diet follow the so-called standard ketogenic diet plan, which provides about 10 percent of your total calories from carbohydrates.
Other forms of ketogenic diets include cyclic ketogenic diets, also known as carb cycling, and targeted ketogenic diets, which allow for adjustments to carbohydrate intake around exercise. These modifications are typically implemented by athletes looking to use the ketogenic diet to enhance performance and endurance and not by individuals specifically focused on weight loss.
But generally speaking, if you plan to follow a ketogenic diet, you should aim to consume less than 10 percent of your total calories from carbohydrates per day. The remaining calories should come from 20 to 30 percent protein and 60 to 80 percent fat. That means if you follow a daily 2,000-calorie diet, no more than 200 of your calories (or 50 grams) should come from carbs, while 400 to 600 calories should come from protein and 1,200 to 1,600 should come from fat. (There’s a reason this plan is also called a high-fat, low-carb diet!)
Is Exercise Involved in the Standard?Ketogenic?Diet?
Although the?ketogenic?diet does not specifically require incorporating fitness into your routine, increasing physical activity is always important when looking to help reduce and certainly maintain a healthy body weight. (15)
For endurance athletes, the transition to a?ketogenic?diet may reduce recovery time after training, but for casual exercisers, the transition to the?ketogenic?diet may make sticking with your fitness routine a challenge at first. (10) If you feel your energy levels drop too much when starting the?ketogenic?diet, slow down your reduction of carbohydrates, making sure to do it over time rather than all at once.
What Side Effects Should You Expect?
To prevent side effects such as the keto flu, begin transitioning your meal plan gradually. Start by understanding how many carbohydrates you take in most days. Then begin slowly reducing your carbohydrate intake over a period of a few weeks while gradually increasing your intake of dietary fat to keep your calories the same. You should also make sure to seek guidance from a professional to make sure this plan works best for you and your health goals. “See a dietitian and adapt the diet to fit your long-term needs,” Spano recommends.
What to Eat on the Standard Ketogenic Diet
The ketogenic diet is not a commercial meal plan, so there are no costs or membership fees associated with starting this diet. But, depending on your current eating habits, this eating approach may increase your food bill.
Because many processed foods would not be considered ketogenic-diet-friendly, a switch to buying more whole, unprocessed foods may seem expensive at the time, especially with the reliance on high-fat and protein-rich foods.
But buying in-season, fresh produce, along with frozen vegetables, which can be just as healthy as their fresh counterparts, can help reduce costs. Although nuts, seeds, and animal proteins such as beef can drive up the cost of the grocery bill, buying in bulk can help lower their cost as well.
The ketogenic diet relies heavily on dietary fat. Because high levels of animal fat in the diet have been associated with increased levels of?cholesterol, aiming to include a good variety of plant-based fats can be helpful. Plant-based oils such as olive oil and avocado oil provide healthy fat for cooking and?dressings. (16)
Adding fat-rich foods such as avocado, nuts, and seeds can all make for healthful options that will provide you with unsaturated fats along with beneficial fiber. Most fruits are restricted on this plan — there are exceptions, including avocado — but?nonstarchy vegetables such as leafy greens should become a staple of your diet.
Lean proteins such as fish, poultry, and grass-fed beef can also be included as a source of?protein?on this diet.
A?List of?Acceptable Foods for the Standard Ketogenic Diet
- Nonstarchy vegetables?like leafy greens, broccoli, cauliflower, cabbage, peppers, mushrooms, and onions
- Dairy,?including eggs and cheese
- Protein?like beef, pork, poultry, fish, shellfish, and soybeans
- Nuts and seeds,?including walnuts, almonds,?pistachios,?sunflower seeds, and pumpkin seeds
- Fats?like plant-based oils and butter
- Fruits?like avocado, berries (in moderation), coconut (in moderation), and rhubarb
Foods You Should Avoid or Limit on the Ketogenic Diet?
- Processed foods?like crackers, corn chips, and potato chips
- Sweets,?including candy, cookies, brownies, and cake
- Grains of all kinds,?including bread, pasta, rice, and quinoa
- High-carb fruits?like melons and tropical fruits
- Artificial sweeteners?such as Equal and Splenda
A Sample 3-Day Menu of the Standard Ketogenic Diet
- Breakfast: Scrambled eggs with sliced avocado
- Snack: Almond butter on celery
- Lunch: Spinach salad topped with canned tuna, olive oil, and vinegar
- Snack: 1 ounce (oz) string cheese and 1 oz pistachios
- Dinner: Sirloin steak paired with sautéed mushrooms, onions, and cauliflower rice
- Breakfast: Mushroom and cheese omelet with sliced bacon
- Snack: ? avocado
- Lunch: Chicken stir-fry with peppers, onions, and peanuts sautéed in peanut oil
- Snack: 1 oz Brie cheese with 1 oz walnuts
- Dinner: Salmon fillet with oven-roasted Brussels sprouts
- Breakfast: Keto smoothie made with avocado, full-fat coconut milk, chia seeds, and nut butter
- Snack: Hard-boiled egg
- Lunch: Cheeseburger (without bun) over a bed of lettuce paired with string beans
- Snack: 1 oz almonds
- Dinner: Chicken breast paired with sautéed broccoli
What to Expect If You Try the Keto Diet
While the keto diet can lead to rapid weight loss through ketosis, the plan carries some health risks, including nutritional deficiencies, heart harms, gastrointestinal issues like constipation, and more. (11, 6, 5)
Due to the health risks involved, experts advise some individuals, such as those with heart disease or?individuals who are at a higher risk for it, against trying the keto diet. People with type 2 diabetes should consult their doctor before attempting the keto (or any new) diet.
Because of the severe carb restrictions and elimination of food groups such as grains, the plan may also be challenging to adhere to in the long run. Trying the diet, giving it up, then trying it again may lead to weight cycling, or yo-yo dieting, in turn making it harder to lose weight overall.
If you are planning to try the keto diet, be sure to consult your healthcare team and, if possible, a registered?dietitian to make sure you meet your nutritional needs with the plan. Working with a professional can help you determine whether you should make adjustments or if you’d be better off avoiding the diet entirely.
Editorial Sources and Fact-Checking
- Carbohydrates and Blood Sugar. The Nutrition Source: Harvard T.H. Chan School of Public Health.
- Low-Carb Diet: Can It Help You Lose Weight? Mayo Clinic. August 29, 2017.
- Dietary Intake for Adults Aged 20 and Over. National Center for Health Statistics: Centers for Disease Control and Prevention. May 3, 2017.
- Gosmanov A, Gosmanova E, Kitabchi A. Hyperglycemic Crises: Diabetic Ketoacidosis (DKA), and Hyperglycemic Hyperosmolar State (HHS). Endotext. May 19, 2015.
- Constipation: Overview. Mayo Clinic. January 10, 2018.
- Anand S, Hawkes C, Souza R, et al. Food Consumption and Its Impact on Cardiovascular Disease: Importance of Solutions Focused on the Globalized Food System. Journal of the American College of Cardiology. October 2015.
- Heart Disease Risk Factors. Centers for Disease Control and Prevention. August 10, 2015.
- Diabetic Ketoacidosis: Overview. Mayo Clinic. August. 21, 2015.
- Mackie GM, Samocha-Bonet D, Tam CS. Does Weight Cycling Promote Obesity and Metabolic Risk Factors? Obesity Research & Clinical Practice. March-April 2017.
- Noakes T, Volek J, Phinney S. Low-Carbohydrate Diets for Athletes: What Evidence? British Journal of Sports Medicine. July 2014.
- Gibson A, Seimon R, Yee C, et al. Do Ketogenic Diets Really Suppress Appetite? A Systematic Review and Meta-Analysis. Obesity Reviews. January 2015.
- Feinman RD, Pogozelski WK, Astrup A, et al. Dietary Carbohydrate Restriction As the First Approach in Diabetes Management: Critical Review and Evidence Base. Nutrition. January 2015.
- Azar S, Beydoun H, Albadri M. Benefits of Ketogenic Diet for Management of Type Two Diabetes: A Review. Journal of Obesity & Eating Disorders. September 2016.
- Paoli A. Ketogenic Diet for Obesity: Friend or Foe? International Journal of Environmental Research and Public Health. February 2014.
- Swift D, Johannsen N, Lavie C, et al. The Role of Exercise and Physical Activity in Weight Loss and Maintenance. Progress in Cardiovascular Diseases. January 2015.
- Siri-Tarino P, Sun Q, Hu F, Krauss R. Saturated Fat, Carbohydrate, and Cardiovascular Disease. The American Journal of Clinical Nutrition. March 2010.