If you could train your body to burn fat, would you? Of course you would. Lucky for you, that’s what the keto diet is all about — burning fat, rather than glucose, for energy.
The ketogenic diet is a high-fat, low carb diet. Over the past few years, keto has grown in popularity as people recognize its benefits for reaching health and fitness goals.
If you’re new to the keto diet, you’re probably wondering, “What is the ketogenic diet all about, and can it work for me?” Below, all your questions will be answered. Use this page as your comprehensive guide for how to start a keto diet.
What Is the Ketogenic Diet?
The ketogenic diet, or “keto,” is a high-fat, low carb diet that puts your body in a fat-burning state known as ketosis. In ketosis your body burns body fat, rather than carbohydrates, for fuel.
Following a diet containing high amounts of fat, moderate amounts of protein and extremely low levels of carbohydrate allows you to change how your body uses energy. To fully understand this shift, it’s important to grasp your body’s usual metabolic process.
Your Body Will Always Burn Sugar Before Burning Fat
When you eat a diet rich in carbohydrates, your body converts those carbs into glucose (blood sugar). Since carbohydrates are turned into sugar, your blood sugar levels rise. When blood sugar levels rise, it signals your body to create insulin, which carries glucose to your cells to be used for energy[*]. This is what is known as an “insulin spike.”
Glucose is the preferred energy source of your body. As long as you keep eating carbohydrates your body will keep turning it into sugar, thereby burning that sugar for energy. In other words, when glucose is present, your body will refuse to burn off its fat stores.
How the Keto Diet Works: Switching From Burning Glucose to Burning Fat
Since carbs are your body’s preferred energy source, the only way to start burning fat is by taking away the carbs. When following the keto diet, you lower your carb intake exponentially. This depletes the glycogen stores (stored glucose) in your body[*]. With no glucose available for energy, your body has no choice but to start burning its fat stores. Your body starts converting fatty acids into ketones, a metabolic state known as ketosis, the basis of a ketogenic diet.
In ketosis, 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 your body. It helps your body function on fat when food is not readily available. Similarly, the keto diet focuses on “starving” your body of carbohydrates, transforming your body into a fat-burning state and supplementing with optimal nutrition.
But Isn’t Fat Bad?
For the longest time, consumers were told fat led to weight gain. Nutrition data from the 1970s labeled saturated fats as bad, causing the United States to enter the era of low-fat products. During this time, obesity in America soared while consumption of fat (particularly saturated fats) plummeted. Low-fat diet products lined grocery store shelves as a high-carb, low-fat diet became the preferred method for weight loss. Yet, people kept gaining weight.
Clearly, something wasn’t adding up.
Today, new studies show that healthy fats are not the real culprit[*]. A ketogenic diet busts the “fat makes you fat” myth 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 your body. In contrast, a low carb diet can help reduce inflammation far better than a low-fat diet[*].
Recent studies show no significant link between saturated fats and the risk of heart disease[*]. In fact, there are many benefits of including healthy saturated fats in your diet. Saturated fat improves HDL and LDL cholesterol levels, maintains bone density, boosts the immune system and supports the creation of important hormones.
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 moderate 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 with. You cycle between periods of eating a low carb diet for several days, followed by a period of eating higher amounts of carbs (typically lasting several days).
High-Protein Ketogenic Diet (HPKD)
This approach is very similar to the standard (SKD) approach. The primary difference is the protein intake. While a standard keto diet will include moderate protein, here you up your protein intake considerably.
Note: The SKD method is the most used and researched version of keto. The majority of the information below pertains to this standard method.
Macro Breakdown: 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:
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% of total carbs. That would come out to 1,500 calories and 167 grams of fat, 400 calories and 100 grams of protein, and 100 calories and 25 grams of carbs.
For most people, a range of 20-50 grams of carbohydrate intake per day is ideal, or 5-10% of total calories. Some individuals can go as high as 100 grams per day and stay in ketosis.
Protein is a necessary component of any diet, helping to maintain muscle mass, prevent injury and promote longevity. To determine how much protein to consume, take into account your body composition and activity level. Most individuals consume 0.7 to 0.9 grams of protein per pound of lean body mass. If you’re a 150-pound female, this would come out to 105 to 135 grams of protein.
After your daily needs for protein and carbohydrates have been calculated (in percentages), total the two numbers and subtract from 100. That number is the percent of calories which should come from fat. If you consume 5% of daily calories from carbohydrates and 20% from protein, the remaining calories, or 75%, will 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.
Using the Perfect Keto Macro Calculator
The above macro guidelines are just that — guidelines. Remember, ketosis is a metabolic state, one that can be easier or more difficult to reach based on your body composition, age, gender, activity level and lifestyle. To get a more accurate depiction of your individual macro goals, use the Perfect Keto macro calculator:
Select the Standard Ketogenic Calculator for a classic ketogenic diet of 75% fat, 20% protein, 5% carbohydrate (recommended)
Select Specialized Macronutrient Calculator to input specific amounts of fat, protein, and carbohydrate
Choose Calculator Type*
Unit of Measurement*
Choose what describes you best
Calorie Intake Goal
Input "0" to maintain your bodyweight
Input a surplus percentage for weight gain
Input a deficit percentage for weight loss
5-10% is a small deficit
10-20% is a moderate deficit
20-30% is a large deficit
Input Your Body Fat %
Input Your Protein Ratio
Guide to picking your protein ratio
To maintain muscle, leave protein ratio between 0.60 to 0.80 grams per lb of lean body mass (1.3 to 1.7 grams per kg LBM)
To gain muscle, the protein ratio should be between 0.8 to 1.2 grams per lb of lean body mass (1.7 to 2.3 grams per kg LBM)
Input Your Total Carb Intake
Input the grams of carbs you want to consume on a daily basis
Your Daily Macronutrient Goals
What’s the Difference Between Keto and Low Carb?
Too often, the keto diet gets lumped in with other low carbohydrate diets, like Atkins. There are a few key differences between them.
Differences in Fat Intake
The main difference between keto and low carb is the macronutrient levels. On keto, you will need to consume over 70% of your calories from fat on a daily basis to enter ketosis. In a low carb diet, there’s no specified daily intake of fat (or other macronutrients).
Differences in Protein Intake
Most low carb diets are also high-protein diets. However, in keto you will only consume a moderate amount of protein, accounting for roughly 20% of your total calories.
Differences in Goals
The goals between the two diets vary. The goal of keto is to enter ketosis, weaning your body off burning glucose for fuel. With a low carb diet, you may never enter ketosis. In fact, some diets cut out carbs for a specified period, only to add them back in.
What to Eat on Keto: The Keto Diet Food List
Now that you understand the basics and science behind the keto diet, it’s time to hit the grocery store. You will enjoy nutrient-dense foods including meat, vegetables, healthy fats and nuts as snacks, avoiding grains, legumes, processed foods and most fruits. Consume these keto-friendly foods while staying within your macro guidelines:
Meat, Eggs and Nuts
All meat and seafood are included on the keto diet, as long as it’s not breaded or fried. Always choose the highest quality meat you can afford, selecting grass-fed and organic beef whenever possible, wild-caught fish, and pasture-raised poultry, pork and eggs. Nuts and seeds are also fine and best eaten raw (not roasted or coated in sugar).
Beef, preferably fattier cuts like steak, veal, roast, ground beef and stews
Poultry, including chicken breasts, quail, duck, turkey and wild game — try to focus on the darker, fattier meats
Pork, including pork loin, tenderloin, chops, ham, bacon and ground
Fish, including mackerel, tuna, salmon, trout, halibut, cod, catfish and mahi-mahi
Shellfish, including oysters, clams, crab, mussels and lobster
Organ meats, including heart, liver, tongue, kidney and offal
Eggs, including deviled, fried, scrambled and boiled — use the whole egg
Vegetarian sources, like macadamia nuts, almonds and nut butter
Low Carb Vegetables
On a keto meal plan, feel free to fill your plate with low carb vegetables. Vegetables are a great way to get a healthy dose of micronutrients, thus preventing vitamin deficiencies on keto. Enjoy low carb vegetables like leafy greens, cruciferous veggies and lettuces, aiming to eat veggies containing less than 5 grams of net carbs per serving.
Approach fruit with caution on keto, as it contains high amounts of sugar and carbohydrates. If you are craving something light and sweet, grab a handful of berries, such as blueberries or raspberries, as a treat.
Enjoy these low sugar fruits:
Avocadoes (the one fruit you can enjoy in abundance)
Organic berries, such as raspberries, blueberries, strawberries and cranberries
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.
Use seasonings freely on keto — just make sure they don’t have any added sugar. To add flavor to dishes, consider purchasing fresh herbs at the store. Pro tip: If you store fresh herbs in a mason jar filled with water in the fridge, they will last up to two weeks.
Foods to Avoid on Keto
The following foods are best avoided on keto due to their high carb content. When starting keto, do a purge of your fridge and cupboards. Donate any unopened items and throw the rest away.
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.
While the micronutrient levels of fruit can’t be denied, they’re not keto-friendly due to copious amounts of sugar. Avoid apples, mangos, pineapple and other fruits (with the exception of berries).
Avoid starchy vegetables like potatoes, sweet potatoes, some squash, parsnips and carrots. Like fruit, there are health benefits to these foods. However, you can find those vitamins and minerals from low carb sources — ones that won’t kick you out of ketosis.
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. If you are craving a dessert, try one of these keto-friendly recipes instead.
Seed oils are heavily processed and can become rancid when heated. Avoid corn oil, canola oil, peanut oil and grapeseed oil. They contain large amounts of omega–6 fatty acids, which are inflammatory in large amounts.
Health Benefits of a Keto Diet
A ketogenic diet has been associated with incredible health benefits beyond weight loss. Keto has been shown to improve memory, provide mental clarity and reduce symptoms associated with various diseases.
Use Keto to Treat Disease
In various studies, researchers have shown that keto can help with the following:
Eliminate diseases related to blood sugar like Type 2 diabetes[*]
Reduce risk factors for heart disease, including improvement in HDL cholesterol, triglycerides and LDL cholesterol (related to plaque in the arteries) [*]
Decrease skin inflammation and lesions in those with acne[*]
Prevent seizure in people, especially children, with epilepsy[*]
Slower tumor growth with patients diagnosed with prostate, pancreatic, brain, lung and gastric cancer[*].
Use 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 for energy.
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 as their bodies adjust to burning ketones.
Use Keto to Improve Metabolic Functions
Studies show multiple long-term metabolic benefits of a keto diet. 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[*].
How to Know When You’re in Ketosis
You can follow the above macro guidelines, eat the prescribed keto diet foods and avoid grains, starches and legumes and still struggle to enter ketosis. Why? Because ketosis is a metabolic state, and you may need to tweak your meal plan, exercise regimen and other lifestyle choices in order to enter it.
There is only way to know you have transitioned into a fat-burning state: Test your ketone levels. There are three ways to do this:
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, with a blood test being the most accurate (but most expensive). 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:
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 body. These minor, but uncomfortable symptoms might include:
If you experience keto flu, drink plenty of water. Increasing your salt intake can also help minimize symptoms. Finally, gradually lowering your carb intake might lessen the negative side effects of keto flu. This will extend the amount of time it takes to get you into ketosis, but will make for a much more pleasant experience.
Those with diabetes should be aware of diabetic ketoacidosis. In ketoacidosis, ketones levels reach an extremely high level, causing the blood to become acidic. 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.
Supplements: Get Into Ketosis Faster
The best way to enter ketosis is through diet. However, if you struggle to get into ketosis, there are two strategies that can help: intermittent fasting and taking supplements. Supplements help you get into ketosis faster or re-enter ketosis after eating too many carbs.
The purpose of exogenous ketone supplements is to provide your body with extra ketones (i.e., energy). Ketone supplements can help you enter ketosis in a matter of hours (rather than days), even after a carb-laden meal.
MCT Oil and Powders
MCT is short for medium chain triglyceride. MCTs are a form of fatty acids, which can then be converted into ketones for fuel. MCTs are the ideal source of energy because they don’t rely on other enzymes for absorption in your body.
If you are an athlete and typically take protein powder, this is one of the few protein powders recommended by Perfect Keto. Most other animal-based protein powders contain casein and whey, which can be inflammatory and hard to digest for some people. Collagen protein from grass-fed beef is filled with amino acids to help your body recover after a workout, without the negative effects of other protein powders.
Ready to Get Started on Keto?
Now that you understand the science behind keto, what foods to eat and what foods to avoid, you’re ready to get started.
Any new diet can be daunting, which is why Perfect Keto has so many resources to help you cook, shop and meal prep on keto. To begin, try these resources:
Dr. Anthony Gustin is a board-certified sports chiropractor, functional medicine practitioner, entrepreneur, podcast host, and founder of Perfect Keto.
Over the last few years, he has treated thousands of patients with movement rehab, internal diagnostics, and natural interventions, including NFL, MLB and NBA champions. After growing his sports rehab and functional medicine clinics to six locations in San Francisco, he shifted his mission to help as many people as possible achieve optimal health and well-being.