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What Is the Ketogenic (Keto) Diet? A Beginner’s Guide

The ketogenic diet, or keto diet, is all the rage these days. Everyone from Kim Kardashian and Megan Fox to ordinary people swear by the low-carb, high-fat eating pattern. There are even food products that line store shelves that are keto-friendly.

While everything seems to be on the up and up on the keto diet, is it really a miracle diet or just the latest fad?

Jennifer Oikarinen, a registered dietitian with Banner Estrella Medical Center in Phoenix shared details of how the keto diet works and whether it’s a right fit for you.

How does the ketogenic diet work?

The keto diet focuses on eating extremely low amounts of carbohydrates, moderate protein and very high fat.

[Also read “Get the Skinny on Fats: The Good, Bad and the Worst for You.”]

The purpose behind this is to shift your body into using stored body fat as a source of energy, known as ketosis, rather than glucose from carbohydrates. When you don’t eat carbs, the liver breaks down fat stores to produce energy in the form of molecules called ketones.

“You’re basically manipulating your body to use ketones for energy instead of carbs by limiting carbohydrate intake, while at the same time achieving weight loss by burning fat stores,” Oikarinen said. “It seems almost too good to be true, which means it probably is.”

Keto shares many similarities with Atkins and other low-carbohydrate diets, but unlike Atkins diets and others, not all low-carb diets are considered keto. “Typically, 70% to 90% of calories come from fat with a keto diet,” Oikarinen said.

The ketogenic diet was originally created to help treat epilepsy. In most recent years, it’s been used as a way of losing weight. However, it’s important to discuss with your health care provider before starting any diet plan.

The different types of ketogenic diets

There are several different versions of the ketogenic diet, with varying amounts of fat and protein. Here are just a few:

Standard ketogenic diet (SKD): This is a low carb, moderate protein and high-fat diet, with 20% protein, 70% fat and only 10% carbs.
High protein ketogenic diet: This eating routine incorporates more protein than SKD, with 35% protein, 60% fat and 5% carbs. 
Cyclical ketogenic diet (CKD): Also known as the recurrent ketogenic diet, CKD involves days in which more carbs are eaten, such as five keto days followed by two higher carb days. 
Targeted ketogenic diet (TKD): This routine is like SKD, but it allows you to have carbs around workouts.

However, only the standard version is the most researched and most recommended.

What can you eat on the ketogenic diet?

Large amounts of:

  • Avocado
  • Coconut
  • Olive oil and other plant oils
  • Nuts, nut butters and seeds
  • Bacon
  • Egg yolks
  • Butter
  • Cheese
  • Animal fats
Small amounts of:
  • Meat and chicken
  • Fish
  • Seafood
  • Eggs

“Keto only allows for a small amount of protein as it consists of only 20% of the diet,” Oikarinen said.

And then very small amounts of low-carb vegetables:
  • Leafy greens
  • Broccoli
  • Asparagus
  • Cucumber
  • Celery
  • Tomatoes
  • Peppers
  • Zucchini

What can you not eat on the ketogenic diet?

  • Grains (like wheat-based products, rice and pasta)
  • Starchy vegetables and high-sugar fruits
  • Low fat or diet products
  • Juices
  • Honey, syrup or sugar in any form
  • Some condiments and sauces (like ketchup and teriyaki sauce)
  • Chips and crackers
  • Baked goods including gluten-free baked goods
  • Alcohol

What are the advantages of the ketogenic diet?

Here are some of the benefits of the ketogenic diet:

Weight loss. You may feel less hungry because fatty foods take a longer time to break down in the body. Weight loss not only comes from ketosis, but it also comes from reducing calorie intake by eliminating certain food groups.

No more low-fat. The keto diet allows you to enjoy foods high in fat, such as red meats, nuts and cheese, while still losing body weight. Remember though the keto diet stresses eating healthy fats with only a small amount of protein. “It’s not an excuse to eat a bunch of steak, bacon and cheese and call it a keto diet,” Oikarinen noted.

Health benefits. The keto diet was originally used as a tool for treating neurological diseases such as epilepsy. Studies have now shown that the diet can have benefits for a wide variety of different health conditions, such as heart disease, high blood pressure, cancer, Alzheimer’s disease and polycystic ovary syndrome (PCOS).

What are the disadvantages of the ketogenic diet?

The keto diet may have some health benefits but staying on the keto diet can have some negative side effects.

Keto flu. Short-term health risks include flu-like symptoms, called the keto flu. Some of the symptoms are often temporary and may include headaches, dry mouth, low blood sugar, fatigue and nausea.

Constipation. “Cutting back on high-fiber vegetables, fruits and whole grains can also increase your risk for constipation,” Oikarinen. “In this case, it may help to take a fiber supplement to help stay regular, but this should be discussed with your provider first.”

Issues with your kidneys. Keto can put stress on your kidneys and put you at higher risk for kidney stones and gout.

“High amounts of animal proteins can make your urine more acidic and increase calcium and uric acid levels,” Oikarinen said. “This combo makes you more susceptible to kidney stones and high uric acid can increase your risk for gout.”

[Also read “Gout Diet: What to Eat and Avoid to Avoid Flare-Ups.”]

Not sustainable long-term. It’s quite difficult to keep your body in a constant state of ketosis. Allowance recommendations can also vary depending on sources. For example, some suggest 10 to 15 grams of carbs for the whole day, which is only about 10 grapes.

“Those who follow the keto diet for medical reasons such as epilepsy are closely followed by a physician and registered dietitian with regular, often weekly follow-ups to guarantee adequate levels of ketones in the body,” Oikarinen said.

Not a good fit for everyone. If you are an insulin-dependent diabetic or have an eating disorder, kidney disease or are pregnant, your provider may not recommend this diet.

“People with type 2 diabetes on certain medications can increase the risk for diabetic ketoacidosis, a dangerous condition that increases blood acidity,” Oikarinen said. “It’s important to talk to your health care provider before starting any new diet.”

Is the keto diet right for me?

While you may see some short-term results, like weight loss, Oikarinen recommended a more balanced approach for long-term weight loss.

“All foods fit into a healthy diet,” Oikarinen said. “Moderation and finding ways to eat the foods you love without overeating is the key.”

As always, talk to your provider or a dietitian if you’re looking to change your diet.

Try out some keto-friendly meals

If you’d like to test out the keto diet without committing, check out some of these keto recipes selected by Delish.


The low-carb, high-fat and moderate protein ketogenic diet can be a great short-term option for some people looking to lose weight, but it isn’t sustainable for some people’s lifestyles. It can be quite restrictive.

For personalized weight management, consult a registered dietitian who can find a meal plan that meets your needs.

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