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What is Keto: Busting the “Fat Makes You Fat” Myth With the Ketogenic Diet

The ketogenic (“keto”) diet is a high-fat, low carb diet currently on the rise as more people recognize its benefits for reaching health and fitness goals. You might be wondering, “What is the ketogenic diet all about, and can it work for me?”

All your questions are about to be answered. You can use this page as your comprehensive guide for everything you need to know about the ketogenic diet and how to get started today.

What is the Ketogenic (“Keto”) Diet?

The purpose of the ketogenic diet is to force the body into a fat-burning state — burning fats instead of carbohydrates for fuel. Those who follow it eat a diet containing high amounts of fat, adequate amounts of protein and low levels of carbohydrates.

Through this breakdown of macronutrients, you’re able to change how the body uses energy. To fully understand the process, it’s important to grasp how the body uses energy in the first place.

How to Switch From Burning Carbs to Burning Fat

When you eat a diet rich in carbohydrates, your body converts those carbs into glucose. This causes an “insulin spike,” as insulin carries the glucose to your bloodstream for energy. Glucose is the preferred energy source of the body. When glucose is present, your body will burn it before burning fat.

A ketogenic diet lowers your carb intake. In turn, your glucose levels lower, so your body can’t convert it to energy. This sends your body into a state known as ketosis, the basis of a ketogenic diet.

Ketosis transforms your body into a fat-burning machine, burning fat (not carbs) for fuel. Specifically, the liver converts fatty acids in your body into ketone bodies, or ketones. This becomes your body’s new energy source. When you increase your fat intake, your body responds by becoming “keto-adaptive,” or more efficient at burning fat.

Ketosis is a natural survival function of the body. It helps your body function on fat when food is not readily available. Similarly, the keto diet focuses on “starving” the body of carbohydrates, transforming the body into a fat-burning state and supplementing with optimal nutrition.

But Isn’t Fat Bad? Busting the “Fat Makes You Fat” Myth

Nutrition data from the 1970s told us saturated fats are bad, causing the United States to enter the era of low fat. During this time, obesity in America soared while consumption of fat (particularly saturated fats) plummeted. Fad, low-fat diet products became the norm at grocery stores as a high-carb, low-fat diet became the preferred method for weight loss. Yet, people kept gaining weight.

Clearly, something was not adding up.

Today, new studies show that fats are not the real culprit[*]. A ketogenic diet dispels the “fat makes you fat” philosophy for several reasons. First, a diet high in carbs (especially refined and processed carbs from low-fat diet products) can increase insulin and blood sugar levels and promote inflammation in the body. In contrast, a low carb diet can help reduce inflammation far better than a low-fat diet[*].

Secondly, saturated fat is not shown to be harmful within the context of a low carb diet. It helps improve cholesterol levels, including increasing the amount of HDL (good) cholesterol while decreasing total triglyceride levels. These two factors help lower your risk of heart disease.

The Different Types of Ketogenic Diets

There are four main types of ketogenic diets. Each one takes a slightly different approach to fat vs. carb intake. When deciding which method works best for you, take into account your goals, fitness level and lifestyle.

The Standard Ketogenic Diet (SKD)

This is the most common and recommended version of the diet. Here, you stay within 20-50 grams of net carbs per day, focusing on adequate protein intake and high fat intake.

Targeted Ketogenic Diet (TKD)

If you are an active individual, this approach might work best for you. Targeted keto involves eating roughly 25-50 grams of net carbs or less 30 minutes to an hour before exercise.

Cyclical Ketogenic Diet (CKD)

If keto seems intimidating to you, this is an excellent method to start off with. Here, you cycle between periods of eating a low carb diet for several days, followed by a period of eating high carb (typically lasting several days).

High-Protein Ketogenic Diet

This approach is very similar to the standard (SKD) approach. The primary difference is the protein intake. Here you up your protein intake considerably.

Note: The SKD method is the most used and researched version of keto. Therefore, the majority of information below pertains to this standard method.

What is Keto: A Beginner’s Guide to the Ketogenic Diet

How Much Protein, Fat and Carbs Should You Eat on Keto?

Fat, protein and carbs are known as macronutrients. When you think of how to build a plate on keto (what each meal will look like), keep this breakdown in mind:

  • High fat
  • Adequate protein
  • Very low carb

Macronutrient Breakdown on Keto

  • Calories from carbs: 5-10%
  • Calories from protein: 20-25%
  • Calories from fat: 75-80% (sometimes more for certain people)

This is a general range, although numbers can vary slightly depending on each person’s needs and goals on the diet.

For example, say someone requires 2,000 calories per day and is eating 75% fat, 20% protein, and 5% carbs. That would come out to 1,500 calories/167 grams of fat, 400 calories/100 grams of protein, and 100 calories/25 grams of carbs. This person would need to make sure they stay at or below 25 grams of carbs each day.

What is Keto: The Beginner’s Guide to the Keto Diet

Carb Intake

For most people, a range of 20-50 grams of carbohydrate intake per day is ideal. Some individuals can go as high as 100 grams per day and stay in ketosis.

Protein Intake

To determine how much protein to consume, take into account your body composition, ideal weight, gender, height and activity level. Ideally, you should consume 0.8 grams of  protein per pound of lean body mass. This will prevent muscle loss.

And don’t worry about eating “too much” protein keto — it won’t kick you out ketosis (yes, really).

Check out the video below by Perfect Keto founder Dr. Anthony Gustin to understand the role protein plays on keto, why we recommend a higher protein intake, and why gluconeogenesis is not a problem:

Fat Intake

After you calculate the percentage of daily calories that should come from protein and carbs, total the two numbers, and subtract from 100. That number is the percent of calories which should come from fat.

Calorie counting is not required on keto, nor should it be necessary. When you eat a diet high in fat, it is more satiating than a diet high in carbs (e.g., sugar). Generally, this cuts down on your chances of overeating. Instead of counting calories, pay attention to your macro levels. For further reading, learn more about micronutrients on a keto diet.

What’s the Difference Between Keto and Low Carb?

The keto diet often gets lumped in with other low carb diets. However, there are a few key differences to note.

Differences in Fat Intake

The main difference between keto and low carb is the macronutrient levels. In most keto variations, 45% of your calories or more will come from fat, to help transition your body into ketosis. In a low carb diet, there’s no specified daily intake of fat (or other macronutrients).

Finally, the goals between the two diets vary. The goal of keto is to enter ketosis, weaning your body off of burning glucose for fuel long-term. With a low carb diet, you may never enter ketosis. In fact, some diets cut out carbs for just a short while, then add them back in.

Foods to Eat on the Keto Diet

Meat, Eggs and Nuts

All meat and seafood are included on the keto diet, as long as it’s not breaded or fried. Enjoy beef, chicken, pork, lamb, goat, turkey and veal. You can also enjoy fatty fish like salmon, tuna, trout and sardines. Always choose the highest quality meat you can afford, whether that means grass-fed or organic. Eggs are always a great choice, preferably free-range. Nuts and seeds are also fine, including almonds, pecans, chia seeds and flax seeds.

Low Carb Vegetables

On a keto meal plan, feel free to fill your plate with low carb vegetables — particularly leafy greens. It’s a great way to get a healthy dose of micronutrients, thus preventing vitamin deficiencies on keto. Options like kale, broccoli, brussels sprouts, asparagus, peppers, spinach and onions are all great options.

Keto-Friendly Dairy

If you can tolerate dairy, it is allowed on the keto diet. Always choose keto-friendly dairy options, which are organic and grass-fed whenever possible. Select full-fat dairy at the grocery store, such as cheese, sour cream, yogurt and heavy cream.

Low-Sugar Fruits

Although you must approach fruit with caution on keto, if you are craving something light and sweet, include berries – such as blueberries or raspberries – in moderation. There is one fruit you can consume abundantly on keto: avocados.

Healthy Fats and Oils

Both animal fats (saturated fats) and plant-based fats can be consumed on the keto diet. Healthy fat sources include butter, tallow and ghee from animals or coconut oil, olive oil, sustainable palm oil and MCT oil from plants.

Herbs and Spices

Use seasonings freely on keto — just make sure they don’t have any added sugar

Wondering how to integrate all of these foods into your daily meals? Check out all our keto recipes!

Foods to Avoid on Keto


Grains are loaded with carbs, so it’s best to avoid all grains on keto. Whole grains, wheat, pasta, rice, oats, barley, rye, corn and quinoa are all out. Instead, try one of these substitutes.

Beans and Legumes

While many vegetarians eat beans for their protein content, they are actually incredibly high carb. Avoid eating kidney beans, chickpeas, black beans and lentils.

Higher-Sugar Fruits

While we can’t deny fruit’s micronutrient levels, they’re not keto-friendly due to copious amounts of sugar. Avoid apples, mangoes, pineapple and other fruits (with the exception of berries).


Avoid starchy vegetables like potatoes, sweet potatoes, some squash, parsnips and carrots. Like fruit, we understand there are health benefits to these foods. However, you can find those vitamins and minerals from more low carb sources — ones that won’t kick you out of ketosis.

Sugar-Laden Products

This includes, but is not limited to, desserts, artificial sweeteners, smoothies, soda and fruit juice. Even condiments are usually filled with sugar, so put down the ketchup and mayo. If you are craving a dessert, try one of the keto-friendly dessert recipes listed on this site instead.


Yes, alcohol is sugar. So set down that glass of wine on keto. If you’re at a social event, follow our guidelines for low carb alcohol.

Seed Oils

Seed oils, particularly when heated, are not a good idea. They contain large amounts of omega-6 fatty acids, which are inflammatory in large amounts.

Health Benefits of a Keto Diet

Since a low carb diet has been shown to have greater effects on weight loss than other diets, it’s a good option for individuals looking to lower their weight, blood pressure and cholesterol. Plus, a ketogenic diet may also help improve insulin resistance and lower glucose levels.

Using Keto to Treat Disease

In various studies, researchers have shown that keto can help with the following:

  • Eliminating diseases related to blood sugar like type II diabetes[*]
  • Reducing risk factors for heart disease, including improvement in HDL cholesterol, triglycerides and LDL cholesterol (related to plaque in the arteries) [*]
  • Decreasing skin inflammation and lesions in those with acne[*]
  • Preventing seizure in people, especially children, with epilepsy[*]
  • Slower tumor growth with patients diagnosed with prostate, pancreatic, brain, lung and gastric cancer[*].

Using Keto to Improve Endurance Levels

The ketogenic diet may help improve endurance levels for athletes. However, it may take time for athletes to adjust to burning fat instead of glucose.

Studies show that aerobic endurance is not decreased with a ketogenic diet[*]. However, athletes who switch to keto might experience limitations in performance at the beginning. This is simply the body adjusting to using fat as its preferred energy source.

Using Keto to Improve Metabolic Functions

Studies show multiple long-term benefits of a keto diet on an individual’s weight and health. Keto significantly decreased body weight, body fat and body mass of individuals in various studies[*]. Keto has been shown to kick your body into a high-performing metabolic state, increasing fat metabolism during exercise[*]. As long as you continue to consume 1-1.2 grams of protein per pound of body mass, you can preserve muscle mass while still burning fat.

How to Know When You’re in Ketosis

Ketosis can be a gray area, as there are varying degrees of it. In general, it can often take around 1-3 days to reach full ketosis.

The best way to monitor your ketone levels is through testing, which you can do from home. When you eat a ketogenic diet, excess ketones spill over into several areas of the body. This allows you to measure your ketone levels in various ways:

  • In your urine with a urine strip
  • In your blood with a glucose meter
  • On your breath with a breath meter

Each method has its advantages and disadvantages, but measuring ketones in your blood is often the most effective. Although it’s the most affordable, urine testing is typically the least accurate method.

For more information on checking your ketone levels, see this article.

Possible Concerns With the Keto Diet

When implementing any new diet — not just keto — it’s important to do so safely, and in a way that supports your unique lifestyle. With this in mind, here are two potential side effects you should know about:

What is Keto: The Beginner’s Guide to Keto


Those with diabetes should be aware of diabetic ketoacidosis. This is a rare but dangerous state for diabetics who don’t take enough insulin, get sick or hurt or aren’t drinking enough fluids. Other causes of ketoacidosis could include alcoholism, an overactive thyroid or true starvation. In ketoacidosis, ketones levels reach an extremely high level, causing the blood to become acidic.

Keto Flu

Within the first two weeks of starting keto, some individuals experience adverse effects known as “keto flu.” This is the result of the sudden removal of carbohydrates from the brain and body. These are minor but uncomfortable symptoms that might include:

  • Mental fogginess
  • Headaches
  • Nausea
  • Weakness
  • Constipation
  • Dizziness

If you experience keto flu, drink plenty of water. Increasing your salt intake can also help minimize symptoms. Another option is to lower your carb intake gradually. This will extend the amount of time it takes to get you into ketosis but will make for a much more pleasant experience.

What is Keto: The Beginner’s Guide to the Keto Diet

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