What Is the Keto Diet?

There are different types of low-carb diets, which are categorized based on their carbohydrate allowance. The ketogenic — or keto — diet is considered a very low-carb diet because carbs are significantly restricted in order to induce a metabolic state called ketosis. 

Some people follow the keto diet in order to promote weight loss, while others use this very-low-carb way of eating to control medical conditions like epilepsy and diabetes. 

Even though the keto diet can benefit health in some ways, it’s notoriously hard to stick to and is linked with a few downsides and risks.

Here’s what you need to know about the ketogenic diet, including what it is, how it impacts your health, and the risks involved with following this popular way of eating. 

Keto Diet Guidelines

According to the Dietary Guidelines for Americans, carbs should make up 45% to 65% of your total daily calorie intake, which equates to 225 to 325 grams of carbs a day for people following a 2,000-calorie diet. 

Although this range is appropriate for some people, others thrive on lower-carb diets. Low-carb diets are eating plans that provide less than 130 grams of carbs per day.

Several eating patterns exist under the low-carb umbrella, including the keto diet.  

As far as low-carb diets go, the keto diet is very restrictive because it limits carb intake to less than 50 grams of carbs per day, which means many foods are off-limits. 

The “classic” ketogenic diet consists of 90% energy from fat, 6-8% from protein, and 2-4% from carbs. Other versions are slightly higher in carbs and protein and lower in fat, but all very low carb diets limit carbs to less than 10% of total calorie intake. 

What Is Ketosis?

The reason why ketogenic diets severely limit carbs is to induce a state of ketosis in the body. Ketosis is a metabolic state that occurs when your body burns fat for fuel instead of carbs. 

Normally, your body uses a type of sugar called glucose as its primary fuel source. Glucose is immediately used for energy or is stored as glycogen in your muscles and liver for later use. However, when you significantly restrict carbs, your body burns through its glycogen stores and is forced to break down fat for energy.  

When in ketosis, your body uses molecules called ketones—which are produced by your liver from the breakdown of fat—as its main energy source. 

When you’re in ketosis, blood ketone levels usually range from 0.5 to 3 mg/dL. The only way to ensure you reach and maintain ketosis while following a keto diet is to measure your ketone levels by testing your urine or blood with specialized ketone testing strips. 

Foods to Eat

When following a keto diet, you must limit your carb intake to less than 50 grams a day in order to reach and maintain ketosis. Keep in mind that some people need to cut their carbs even further to reach ketosis. 

In order to hit the recommended macronutrient—the type of food that’s required in large amounts in the diet—for the keto diet, most of your food intake needs to come from fat. Moderate amounts of protein and high-fiber, low-carb vegetables are allowed as well.

Here’s a list of foods to eat if you’re following a keto diet:

• Fats: Olive oil, avocado oil, coconut oil, avocados, ghee, and unsweetened coconut 
• Non-starchy vegetables: Broccoli, spinach, lettuce, zucchini, onions, cauliflower, tomatoes, cucumbers, artichokes, cabbage, and asparagus 
• Proteins: Eggs, steak, chicken, turkey, and low-carb protein powders 
• Full-fat dairy: Cheese, yogurt, and kefir 
• Nuts and seeds: Pecans, Brazil nuts, macadamia nuts, no-sugar-added peanut butter, pumpkin seeds, hazelnuts, and walnuts 
• Limited amounts of low-carb fruits: Raspberries, blackberries, lemons, coconut meat, and strawberries
• Carb-free drinks: Unsweetened coffee, herbal teas, water, and sparkling water 

Foods to Avoid

When you’re on a keto diet, foods that are high or moderately-high in carbs are out. Even healthy high-carb foods like fruits and root vegetables need to be restricted in order to stay within your allotted carb count. 

Here’s foods and drinks to avoid while on a keto diet:

• Bread and high-carb baked goods: Rolls, muffins, and bagels
• Grains: Rice, oats, quinoa, and couscous 
• Pasta and noodles 
• Sweeteners and sugary foods: Maple syrup, table sugar, cakes, ice cream, cookies, and sugary cereals
• Snack foods: Potato chips, crackers, and granola bars
• Starchy vegetables and legumes: Potatoes, butternut squash, black beans, lentils, and chickpeas
• Fruits and fruit juice: Apples, pineapple, bananas, and orange juice 
• Sweetened drinks: Soda, sugary coffee drinks, chocolate milk, and energy drinks
• Higher-carb alcoholic drinks: Beer and sugary mixed drinks
• Sugary condiments: Sweet salad dressings and barbecue sauce 

Keep in mind that some higher-carb foods, like fruit, can be consumed in small quantities as long as you don’t exceed your daily carb limit. 

The Benefits of Keto

The keto diet is associated with a few health benefits. Here’s more about how the keto diet can support weight loss, reduce blood sugar, and improve certain medical conditions. 

Supports Weight Loss

Studies show that the keto diet is effective for promoting fat loss. 

In a 2022 review that included eight studies in people with type 2 diabetes found that following a ketogenic diet for three months to two years led to significant reductions in body weight and waist circumference.  

However, it’s unclear if the keto diet is more effective for weight loss compared to other, less restrictive diets. 

In a 2022 study, researchers compared the effectiveness of the Mediterranean diet versus a very low-calorie keto diet (VLCKD) for promoting fat loss in 268 people considered overweight or obese. At the end of the study, it took people following the Mediterranean diet three months to achieve 5% weight loss while people following the VLCKD took just one month to achieve the same weight loss.

However, even though the VLCKD resulted in more rapid weight loss, the Mediterranean diet resulted in greater fat loss, a reduction in waist circumference, and a greater increase in muscle mass. The VLCKD provided only 800 calories a day while the Mediterranean diet provided between 1,500 to 1,700 calories per day.  

This means that a low-calorie keto diet could be effective for supporting quick weight loss, but less restrictive higher-calorie diets could be even more effective for reaching a healthier body composition over a longer time period. Plus, higher-calorie diets that provide nutritious foods like fruits, legumes, and higher-carb vegetables are much healthier for your body and are easier to stick to long-term. 

Can Reduce Blood Sugar Levels 

One of the most popular uses for a keto diet is to reduce blood sugar levels in people with diabetes. Because the keto diet cuts out high-carb foods, it helps support blood sugar management and has been shown to drastically improve both short and long-term blood sugar control.

A 2022 review that included eight studies in people with type 2 diabetes found that keto diets significantly reduced hemoglobin A1c (HbA1c), which is a long-term marker for blood sugar control. 

Another 2022 study found that 12 weeks of a keto diet was more effective for reducing fasting blood sugar and HbA1c in people with type 2 diabetes compared to a standard diabetic diet. However, the ketogenic diet was much harder for the participants to stick to compared to the less restrictive diet.  

Keep in mind that less restrictive diets like more moderate low-carb diets, have also been shown to be effective for controlling blood sugar.

Effective for Lowering Triglycerides 

Triglycerides are a type of blood fat that commonly increases when blood sugar levels are elevated.

Having high triglyceride levels can increase your risk of heart disease and type 2 diabetes.

Restricting carb intake seems to be an effective way to lower triglyceride levels. Multiple studies have shown that people with high triglyceride levels who follow keto diets experience significant reductions in triglycerides, which can help reduce heart disease risk.

However, some studies suggest that this reduction may only last a short time as the benefit seems to taper off after three months. 

Effective for Managing Certain Medical Conditions

The keto diet has been shown to be effective for managing certain medical conditions, including type 2 diabetes, epilepsy, Alzheimer’s disease, and polycystic ovarian syndrome (PCOS). 

The keto diet was originally developed to manage drug-resistant epilepsy and has been used since the 1920s to control seizures. 

In addition to epilepsy, the keto diet is now recommended for people with other medical conditions. Although more research is needed, the keto diet shows promise for improving outcomes like daily function and quality of life in people with Alzheimer’s disease.

It’s also been shown to improve blood sugar, weight loss, and insulin resistance in people with diabetes and PCOS.

The Risks of Keto

Although the keto diet may be helpful for some people, it’s highly restrictive and hard to stick to long-term. Because the keto diet cuts out so many nutritious foods, it’s commonly low in nutrients like calcium, fiber, and some B vitamins. Deficiencies can develop if the diet isn’t properly planned. 

What’s more, the keto diet is associated with a few side effects, including headaches, constipation, fatigue, bad breath, and insomnia. However, these side effects usually resolve once a person becomes adapted to this very low-carb way of eating. 

Following a ketogenic diet long-term could result in fatty liver, low blood protein levels, high cholesterol levels, and kidney stones. 

Additionally, ketogenic diets aren’t safe or appropriate for certain people, such as those with medical conditions like liver failure, pancreatitis, and carnitine deficiency. Women who are pregnant or are trying to become pregnant shouldn’t follow a keto diet unless it’s medically necessary. Studies show that pregnant women who follow ketogenic diets are more likely to give birth to babies with neural tube defects, which could be due to the lack of folate in very low-carb diets.

If you have a medical condition like diabetes and want to try a keto diet, make sure to talk to the healthcare provider who manages your condition first. The keto diet is highly restrictive and may not be safe or necessary for many people. Your healthcare provider may be able to recommend a less restrictive diet that includes more foods linked with improved health and decreased disease risk like fruits, a wide variety of vegetables, and legumes. 

A Quick Review

Keto diets are very low in carbs, very high in fat, and moderate in protein. They’re popular amongst people who want to manage their blood sugar and lose weight. Plus, keto diets have been shown to benefit people with certain medical conditions like PCOS, epilepsy, and type 2 diabetes.

However, keto diets are extremely restrictive and difficult to follow and are linked to both short-term and long-term side effects.

Although the keto diet may be appropriate or even necessary for some people, most people can improve their health using less restrictive methods, such as more inclusive moderate- to low-carb diets.