One enduring buzzword to hit the diet world seems to be "keto" — referring to the high-fat, low-carb ketogenic diet. With claims that you can eat all the fat you want, never feel hungry again, 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.
How Does the Ketogenic Diet Work?
As the Harvard T.H. Chan School of Public Health explains, 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.
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.
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, producing ketones, which are by-products of your metabolism. These ketones are then used to fuel the body in the absence of glucose.
Types of the Ketogenic Diet
The ketogenic diet has various modifications. The majority of individuals who follow a ketogenic diet follow the standard ketogenic diet plan, which provides about 10 percent of your total calories from carbohydrates.
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!)
Today’s versions of the keto diet allow you to eat protein more liberally — about 20 percent of your total calories — but keep carbohydrates restricted to 10 percent or less. Northwestern Medicine indicates some of the aims of the modern ketogenic diet are weight loss, weight management, and improved athletic performance.
Classic keto: Sometimes called the therapeutic keto diet, this iteration was developed a century ago to manage seizure disorders; carbohydrates and protein combined make up less than 20 percent of your daily calories, while 80 to 90 percent of calories come from fat. That's according to the Epilepsy Foundation.
Target keto: This option allows 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.
Cyclical keto: Also known as “keto cycling,” this form of the diet typically involves staying on the keto diet for five days and then two days of higher carb intake.
If you search online for the term "keto diet," you'll find a lot of health claims associated with it. But before you give this approach a try, it's important to know what the science suggests about how it may affect your health. Here are possible health benefits of a keto diet.
Possible Improvements in Athletic Performance
A 2014 article found that ketogenic-type diets allowed endurance athletes to rely mostly on stored fat for energy rather than having to refuel with simple carbohydrates during endurance training and competition, and saw improved recovery times.
That said, a 2020 review concluded that while the keto diet may help athletes reduce their weight and body fat, there is no conclusive evidence that the method of eating improves or harms health and performance.
Better Blood Glucose Control in Type 2 Diabetes
For individuals with diabetes, adopting a very low carbohydrate diet, such as the ketogenic diet, may offer some benefits when it comes to glucose management. A 2021 review looked at more than a dozen studies on keto diets and found that they can lower blood sugar levels and reduce the need for medication in people with type 2 diabetes.
If you're looking to lose weight, one benefit the ketogenic diet may offer is appetite suppression. A review of this form of eating showed that while dieting usually increases levels of a hormone that makes you feel hungry, that isn't the case with keto. But exactly why this is needs further study.
Very low calorie ketogenic diets may help people who are overweight or have obesity reduce their BMI, decrease the circumference of their waist, and lower their levels of A1C, total cholesterol, triglycerides, and blood pressure, notes a review and meta-analysis published in 2020.
But when it comes to weight loss — one of the biggest keto selling points 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."
Chris Mohr, RD, PhD, a sports dietitian based in Louisville, Kentucky, and the co-owner of MohrResults.com, 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." That said, the calorie reduction isn't always the case, as it can be easy to consume more calories overall if you're eating more calorie-dense foods (namely fat). One small 2021 study found that people ate almost 700 fewer calories per day on a plant-based low-fat diet than on a low-carb one consisting of mostly animal fat.
Keto Flu
One of the most common side effects of the ketogenic diet is "keto flu." Some people may experience headaches, fatigue, dizziness, sleep problems, heart palpitations, cramps, and diarrhea as the body adjusts to a low-carbohydrate diet. During keto flu, the body's stored glucose begins depleting, and it starts adapting to producing and utilizing ketones as energy. According to Harvard Health Publishing, these side effects usually diminish and resolve in a week or so. To lessen these effects, consider gradually lowering your carbohydrate intake and increasing your dietary fat intake.
Eliminating food groups can be problematic. "Ketogenic diets are often low in calcium, vitamin D, magnesium, and folic acid, which over time can lead to nutrient deficiencies if the diet is not planned carefully," adds Marie Spano, RD, a sports performance nutritionist in Atlanta.
You May Harm Your Heart
Research shows that a diet rich in animal fats and proteins may negatively impact heart health. "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, high blood pressure (hypertension), or a strong family history of the disease — you should speak with a healthcare provider before starting this diet.
The diet's heavy reliance on fat, especially saturated fat, can raise cholesterol levels, further increasing your chances of developing heart disease in the future.
Some research has found low-carb and very low carb plans (which keto fits into) have mixed effects on blood cholesterol levels, with some studies finding that these diets raise cholesterol.
Low Blood Sugar With 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.
Weight Cycling
One of the biggest concerns of the ketogenic diet may be 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 is associated with poorer cardiovascular health, especially among premenopausal women, according to one study.
Most foods needed for the keto diet are easily accessible. Since the diet is high fat, choose healthful options like avocado, nuts, and seeds that will provide you with unsaturated fats along with beneficial fiber. Most fruits are restricted on this plan — there are exceptions, including avocado — but non-starchy vegetables such as leafy greens should become a staple of your diet. Lean proteins such as fish, poultry, and grass-fed beef can be included as a source of protein on this diet.
Top Foods to Eat
Nonstarchy vegetables like leafy greens, broccoli, cauliflower, cabbage, peppers, mushrooms, onions, and rhubarb
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), and tomatoes
Foods to Avoid or Limit
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
Here are the foods every ketogenic diet beginner should try adding to their grocery list.
Proteins
Poultry
Red meat
Seafood
Nuts and seeds
Soybeans
Produce
Spinach
Asparagus
Bean sprouts
Eggplant
Squash
Eggs and Dairy
Eggs
Cheese
Butter
Greek yogurt
Condiments
Salt
Pepper
Mayonnaise
Mustard
Hot Sauce
Drinks
Tea
Coffee
Water
Nondairy milk
Coconut Water
Day 1
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
Day 2
Breakfast: Mushroom and cheese omelet with sliced bacon
Snack: ½ 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
Day 3
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
Day 4
Breakfast: Sliced hard-boiled egg with one teaspoon crumbled feta cheese on top and two slices turkey bacon
Snack: Nuts mixed with blueberries
Lunch: Turkey breast with roasted broccoli
Snack: Guacamole with kale chips
Dinner: Chicken breasts with roasted asparagus
Day 5
Breakfast: Fried egg topped with a slice of cheddar cheese served in between two chicken sausages
Snack: Olives and feta cheese
Lunch: Tuna salad wrapped in lettuce leaves
Snack: Baked buffalo chicken wings
Dinner: Philly cheesesteak lettuce wraps
Day 6
Breakfast: Keto smoothie made with cocoa powder, spinach, almond milk, and protein powder
Snack: Low-carb vanilla yogurt with almonds
Lunch: Meatballs with low-carb pasta and marinara sauce
Snack: Baked cauliflower buffalo bites
Dinner: Bell pepper stuffed with ground turkey
Day 7
Breakfast: Keto pancakes with three sliced strawberries
Snack: Turkey roll-ups with cheese
Lunch: Cauliflower rice with chicken fajita
Snack: Kale chips with hummus
Dinner: Shrimp with bell pepper kebabs
Here are some other things to know before you try this restrictive eating plan.
Know what to eat and avoid. To get the most from this diet it is vital to know which foods are high in carbohydrates, protein, and fat, and choose the most nutrient-dense ones.
Seek professional help. Work with a registered dietitian to ensure you follow this diet healthily without increasing your risk for complications or adverse side effects. You can find a registered dietitian at EatRight.org.
Understand the side effects. Some individuals may experience lethargy, mental fog, constipation, or potentially diarrhea because of a change in fiber intake when starting on a keto diet. As you adjust, these symptoms should dissipate if they do not speak with your healthcare provider.
Plan your start date. Because there may be side effects, pick a start date without deadlines and when you can rest as needed.
Stick with it. It's important to remember that any dietary change aims to promote a healthy lifestyle, so 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.
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, which will make it harder to lose weight permanently.
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 on 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.
