What is the keto diet, and should you follow it?

last updated: May 10, 2021

6 min read

So you’ve heard about the keto diet and have been wondering if it would be the right fit for you. 

Following a ketogenic diet may offer a wide range of health benefits, but what does the research say about the keto diet? This article will define the keto diet and how it works, along with the benefits and risks of the keto diet, who it’s for, and tips for following it.

What is the keto diet?

The ketogenic diet or keto diet is a very low-carb and high-fat diet. These dietary changes were initially designed to treat epilepsy and prevent seizures. However, advancements in medications for seizures lowered the keto diet’s use, except for patients whose condition is resistant to anti-seizure drugs (Wheless, 2008). 

Over the past few decades, the keto diet has re-emerged in popularity for other uses, like weight management and type 2 diabetes management. 

How does the ketogenic diet work?

Macronutrient counting is the base of the ketogenic diet.

Tracking how many grams of fat, protein, and carbohydrates you eat tells you if you are on track to be in ketosis, which we’ll explain below. The important part of macro tracking is to monitor the ratio of fat to protein plus carbs. 

The goal in the ketogenic diet is a ratio of three grams of fat for every one gram of protein and carbs you have. Controlling this ratio affects your metabolism, forcing your body to burn fat for the primary energy source.

Typically, this is done by drastically decreasing your total carbohydrate intake to less than 50 grams per day, shifting your body from using carbs for energy to ketosis.

OC What is the keto diet, and should you follow it? image 11cfdff3-69ca-414a-ba83-7f3d1261787f

What is ketosis?

Ketosis is a type of metabolism that uses fat as the primary energy source and produces ketones to replace glucose (carbohydrates).

Usually, carbs are the primary energy used by the cells, especially for the brain and central nervous system. However, when following a low-carb diet, the body instead uses ketones, a breakdown product of fats (Masood, 2020).

Ketosis can naturally happen in people with uncontrolled diabetes. Diabetic ketoacidosis is a dangerous condition where many ketones are produced because the body isn’t able to use sugars well for energy. When this happens, it changes the pH of the blood, which can lead to several problems that need emergency care (Lizzo, 2021). With the ketogenic diet, the number of ketones produced is ideally smaller and stays within a safe level, not affecting blood pH levels.

Some people on the ketogenic diet will test themselves to monitor their level of ketosis. Ketone blood, urine, and breath tests track the level of ketones and monitor for ketosis. Urine tests use a strip to check for ketone levels and may be the most convenient test to use for most people. 

Benefits of the keto diet

Research shows there may be some benefits to following a ketogenic diet, including: 

Epilepsy and seizures

Epilepsy is a condition that causes disorganized nerve activity, leading to seizures. It can be caused by genetic disorders or an injury to the brain. Some people have epilepsy that is resistant to medications, and the keto diet can be effective in helping to manage seizures in some of these people (Wheless, 2008). 

Heart disease

There’s conflicting information about the benefits of the keto diet for heart disease. Still, some research shows that following a keto diet may help lower blood pressure levels and better manage hypertension (Batch, 2020). 

The keto diet may improve cholesterol levels and the ratio of “good” to “bad” cholesterol. Some studies showed an increase in high-density lipoproteins (HDL), also called “good” cholesterol, and lower triglyceride levels (Batch, 2020). 


Diabetes is caused by changes in the body’s production of or response to the hormone insulin. It results in difficulty controlling blood sugar levels. Carbohydrates break down into sugar during digestion, so low-carb diets have been tested to help manage blood sugar levels.

The ketogenic diet could help control blood sugar levels and help with lowering your hemoglobin A1C. This measurement shows your average blood sugar level for the past three months (Batch, 2020).

Weight management

The keto diet has shown some benefits in helping with weight loss and maintaining a healthy weight. It may also help individuals with obesity and metabolic syndrome reduce the side effects of those conditions (Masood, 2020).

Alzheimer’s disease

People with diseases that affect the brain, such as Alzheimer’s dementia, may benefit from the ketogenic diet. Early research shows ketone bodies may help to protect nerve and brain cells from damage caused by aging (Rusek, 2019). 

Risks of the keto diet

Following a ketogenic diet may have some negative health effects. However, there is still limited information about how this diet affects health long term. Here are some of the risks of following a ketogenic diet.

Heart disease risk

Yes, heart disease falls within both the potential benefits and risks of the keto diet.

The research is conflicting on how the keto diet affects heart health. Though we saw that the keto diet might increase HDL cholesterol (“good” cholesterol), some data also show significant increases in low-density lipoproteins (LDL), the “bad” cholesterol. High LDL levels could increase the risk of developing plaques that clog blood vessels (Batch, 2020).

Keto-flu symptoms

You may go through the symptoms of what is commonly known as the keto-flu when adjusting to the ketogenic diet. Some people experience symptoms like:

  • Nausea and vomiting

  • Headaches

  • Difficulty concentrating

  • Constipation or diarrhea

  • Fatigue

  • Difficulty exercising

These symptoms usually begin within a week of starting a ketogenic diet and can last up to a month. 

Keto rash

The keto rash is a rare skin condition that is poorly understood. It is known as prurigo pigmentosa and is associated with ketosis. It doesn’t happen often and hasn’t been studied in depth. 

A few case studies found an itchy, red rash that began after starting a ketogenic diet and cleared after reintroducing carbs to the diet (Alkeraye, 2019; Maco, 2018). 

Difficulty exercising

Intense workouts, like high-intensity interval training, sprinting, and other exercises that make you lose your breath, use a type of metabolism that doesn’t use oxygen and requires carbs. Because it limits carbs so much, the ketogenic diet may decrease exercise performance and make intense exercise more difficult (Harvey, 2019). 

Low blood sugar

The ketogenic diet may increase the risk for low blood sugar in people with diabetes, especially for people with type 1 diabetes. Medications and blood sugar levels need close monitoring if following a very low-carb diet because low blood sugar levels can cause serious health effects (Batch, 2020).

Other risks

Following a keto diet may lead to other risks such as:

  • Pancreatitis

  • Kidney stones

  • Fatty liver disease

  • Vitamin and mineral deficiencies

The ketogenic diet may be recommended for people who:

  • Have epilepsy resistant to medication management

  • Have overweight or obesity

  • Have uncontrolled diabetes

If you plan to try the ketogenic diet, talk with a healthcare provider to help you monitor how the ketogenic diet is affecting your health. 

Some people are at a higher risk for adverse health effects from the ketogenic diet. Here are some examples of conditions where the ketogenic diet may not be recommended (Batch, 2020):

  • Liver failure

  • History of pancreatitis

  • Difficulty metabolizing fat

  • People taking medications affecting their blood sugar level

What to eat on a keto diet?

You’ll want to eat mostly healthy fats and high protein foods on a keto meal plan. Here are some examples of keto-friendly foods:

  • Meat—fish, red meat, chicken, turkey, bacon, and sausage

  • Eggs

  • Dairy—cheese, cream, and butter

  • Seeds and nuts

  • Avocados

  • Healthy oils—olive oil, coconut oil, medium-chain triglyceride (MCT) oils, etc.

Fruits and veggies are limited because you will want to keep your net carbs below 50 grams per day (Masood, 2020). Net carbs are the total grams of carbs in a food minus the grams of fiber. 

Fiber isn’t digested like other carbs because humans lack the necessary enzymes to break them down. So, you can subtract the grams of fiber from your total carbs. On the keto diet, it’s encouraged to eat plenty of non-starchy, low-carbohydrate vegetables.

Small servings of certain fruits, like berries, are allowed because they are high in fiber.

Foods to avoid on the keto diet

Any foods that are high in carbs need to be limited on the ketogenic diet. Here is a list of foods to avoid or limit on the keto diet:

  • Sugary drinks—juice, soda, fruit smoothies, and sugary coffee drinks

  • Dessert—cake, brownies, candy, ice cream, etc.

  • Condiments—ketchup, barbeque sauce, honey mustard, honey, etc. 

  • Fruit—unless the net carbs are small (as in the high fiber fruits mentioned above)

  • Beans and legumes

  • Starchy vegetables—potatoes, sweet potatoes, corn, peas, etc.

  • Alcohol—beer, wine, and liquor

  • Low-fat substitutes (low-fat cheese and yogurt)

  • Sweeteners

Is the ketogenic diet healthy long-term?

The keto diet has some small, short-term studies to support potential health benefits, but it hasn’t been studied for its long-term health effects (Batch, 2020).

A common limitation to the diet is its difficulty to sustain long term. Because it is a restrictive diet, many people find it difficult to follow for long periods. If you want to try the ketogenic diet, talk with your healthcare provider and consult with a dietitian to see if the keto diet is the right plan for your health.


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

May 10, 2021

Written by

Ashley Braun, RD, MPH

Fact checked by

Steve Silvestro, MD

About the medical reviewer

Dr. Steve Silvestro is a board-certified pediatrician and Associate Director, Clinical Content & Education at Ro.

Get access to weight loss medications, if prescribed.

Start now