Research-Based

The Ultimate Guide to the Ketogenic Diet

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By Leslie Waterson

Reviewed by Juliana Tamayo, MS, RDN - Last Updated

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INTRODUCTION TO THE KETOGENIC DIET

Glucose is one of the body’s fuels, but ketones are another. A ‘ketone’ is what fat is called when it is used as fuel, and ketones are produced in the liver. The ketogenic (keto) diet involves eating high-fat, low-carb foods, which causes the body to burn fat rather than sugar. When the body is burning fat, this is called being in the state of ketosis. The quickest way to enter ketosis is to fast, but since we obviously need to eat sometimes, a ketogenic diet can help you stay in ketosis.

Many doctors recommend the ketogenic diet and it has been shown in dozens of studies to offer weight loss benefits, reverse type II diabetes, help slow cognitive decline, and improve overall health and physical performance.

HISTORY OF THE KETOGENIC DIET

The ketogenic diet is more than a hundred years old and it was originally developed to control seizures in epileptics. It was noticed that fasting (not eating) helped to control seizures. But fasting can only be done for a limited amount of time, and a few doctors drew the connection between fasting and a low-carb, high-fat diet as a way to produce the same effect without starving the patient. The diet fell out of favor with the development of anti-seizure medications, but bodybuilders in the 1950s and 60s knew about the principles and some adhered to them. The diet remained niche into the 1980s even though big names like Arnold Schwarzenegger wrote about it. The keto diet started to rise in popularity in the 1990s, and in the new millennium, influencers like Gary Taubes, Joe Rogan and Tim Ferriss have made keto mainstream.

KETO DIET MACROS

The macros for the Standard Keto Diet (SKD) are 70-80% fats, 15-20% proteins and 5% carbs.

Consuming very few carbs forces the body into ketosis, or a state of fat-burning. Protein is also kept at a moderate level due to the body’s ability to convert it into glucose, called gluconeogenesis, which can push the body out of ketosis.

There are variations on the SKD, including the Cyclic Keto Diet, Targeted Keto Diet, and the Restricted Keto Diet, but all of them involve eating few carbs, medium protein, and plenty of healthy fats.

BENEFITS OF THE KETO DIET

WEIGHT LOSS

With obesity rates soaring, the search for a new diet has never been more urgent. The keto diet has been shown to help people lose weight fast, which can have a positive effect psychologically, and help you stick to the diet. Weight loss on the keto diet also tends to come from the abdomen, helping to reduce dangerous fat that is squeezing your vital organs.

REVERSE TYPE II DIABETES

Diabetes rates are also skyrocketing. As of 2015, some 30 million Americans or 10% of the population had type II diabetes, and 2/3 of them did not know it. Diabetes is the 7th leading causes of death in America, and an underlying or contributing factor in hundreds of thousands of other deaths. The keto diet has been shown in many studies to reverse type II diabetes.

IMPROVE COGNITIVE FUNCTION

Ketones are a clean-burning fuel for the body, which helps to improve mental clarity and cognitive function. The keto diet has also been shown to offer benefits to those with Alzheimer’s, Parkinson’s, and age-related neurodegeneration.

CURB HUNGER

Not all calories are created equal. One of the hardest things about sticking to a diet is feeing hungry and unsatisfied. By eating plenty of fat but very few carbs, the hormones that signal hunger get switched off, and the ones that send the sign that we feel satisfied get turned on.

IMPROVED NUTRITION

While it may be possible to stay in ketosis by eating fast-food burgers, this certainly isn’t recommended or a good idea. Making the changes to diet that contains lots of quality high-fat foods like olive oil, avocados, fatty fish and meats and getting most of your carbs from fresh vegetables will automatically improve your nutrition.

LOWER INSULIN LEVELS

High levels of insulin signal to the body to store fat, but when you’re in ketosis and your body has very few carbs to process, insulin levels remain low. This helps to prevent metabolic syndrome (a precursor to type II diabetes) as well as promote the release of good hormones, like human growth hormone (HGH).

CONSERVE YOUR PROTEIN

Being in ketosis means your body uses fat rather than glucose as fuel, and does not pull proteins from your system through a process called gluconeogenesis to burn. This means your proteins can be used for more important functions, like building muscle.

NO MORE BLOOD SUGAR SWINGS

Carbs wreak havoc with your blood sugar and, consequently, your mood. A spike in blood sugar and the ensuing crash can cause you to eat anything you can get your hands on, leading to the next spike and crash. By following the keto diet, you can say goodbye to the sugar rush rollercoaster ride.

IMPROVES CHOLESTEROL LEVELS

HDL or ‘good’ cholesterol is likely to increase on the keto diet, and LDL or ‘bad’ cholesterol is likely to decrease. Triglyceride levels are also likely to drop. While some people experience an elevation in total cholesterol levels, it is usually due to an increase in the ‘good’ kind.

MAY LOWER BLOOD PRESSURE

Hypertension or high blood pressure has been correlated to stroke, heart disease and kidney failure. Low-carb diets have been shown in studies to reduce blood pressure, reducing your risk of developing these potentially life-threatening illnesses.

DOWNSIDES OF THE KETO DIET

KETO FLU

Initially, keto can be hard to do as your body gets used to switching from burning glucose to burning fat. You may experience fatigue or ‘brain fog’ while your metabolism readjusts. But you can help minimize the discomfort by staying hydrated and adding electrolytes to your diet.

CHANGES IN BLOOD LIPIDS

As mentioned in the ‘pros’ section, cholesterol levels may change when you switch to a keto diet, but this is not necessarily a bad thing. Your numbers will likely improve overall with HDL levels rising (the good kind of cholesterol) and LDLs and triglycerides (the bad kind) going down. It’s more a matter of working with a doctor who isn’t brainwashed with the old way of thinking that all cholesterol is bad.

VITAMIN DEFICIENCIES

Dietary changes can make it hard to get all your vitamins. To prevent any deficiencies, take a multivitamin supplement, and consider adding fiber to your diet.

SOCIAL CHANGES

It can be hard to stick to the keto diet if you are surrounded by people slurping on sugary coffee drinks and chowing down on fries, pizza, and other junky (but tasty) foods. Find non-food-related activities to do together, such as taking a walk, instead.

KETO DIET DETAILS

On the keto diet, carbs are kept to under 20 grams per day, and the lower the better. The majority of carbs should come from green vegetables.

Protein is also eaten in moderate amounts only, as it is possible for the body to convert protein into sugar, and should account for about 15-20% of your total caloric intake.

Fat will comprise the majority of your calories, and ideally it will come from fresh, healthy sources. Animal proteins are good, and be sure to choose the healthiest ones you can find. Fast-food burgers can do in a pinch but should not be a regular feature of keto or any healthy diet.

BEST FOODS TO EAT ON THE KETO DIET

keto foods
  • Meat & poultry — Fatty is better, and organic, pasture-raised is best.
  • Fish — Again, fatty is best, and so is wild-caught.
  • Eggs — Eggs provide healthy fat and protein and are very versatile.
  • Non-starchy vegetables — Green, leafy vegetables provide micronutrients and fiber.
  • Nuts & seeds — These can add crunch and flavor to a salad, and make a convenient snack.
  • Full-fat dairy — Cream, butter, Greek yogurt and the like are delicious sources of healthy fat.
  • Healthy oils — Fat is king with keto. Healthy fats include coconut, olive, avocado, sesame, and MCT (medium-chain triglycerides).
  • Natural sugar-free sweeteners — Stevia can help satisfy that sweet tooth when you’re first starting out on keto.
  • Fresh herbs and spices — Herbs, spices, salt, pepper, and lemon juice are all tasty, low-carb ways to season your food.
  • Tea & coffee — Unsweetened, but you may add heavy cream if you like. Many keto dieters like Bulletproof coffee, or make their own with MCT oil and butter.

FOODS TO AVOID ON THE KETO DIET

  • Sugar — In all its forms, sugar should be avoided, including natural ones such as honey, agave and maple syrup.
  • All processed ‘white’ foods — This includes things such as bread, pasta, cookies, crackers, pastries and the like.
  • Sweetened beverages — Soda (diet too), sports drinks and coffee drinks are to be avoided.
  • Grains — Grains are not part of the keto diet: no wheat, oats, rice, corn, quinoa, and all of its forms, like tortillas, bread, noodles, etc.
  • Starchy vegetables — Things like potatoes, sweet potatoes, corn, winter squash are to be avoided.
  • Beans & legumes — These are also starchy and therefore not on the keto diet.
  • Fruit — Fruit is high in sugar, especially highly-cultivated, oversize fruits. Small amounts of in-season berries such as blueberries or blackberries can be enjoyed in moderation. Lemon or lime juice can be added to water or used as a salad dressing.
  • Condiments — Items like ketchup, barbecue sauce, dipping sauces and many salad dressings contain a lot of sugar. The best options for commercial salad dressing are blue cheese and Caesar, but a better keto option is olive oil and and a squeeze of lemon.
  • Unhealthy fats — Not all fat is created equal. Fats such as hydrogenated oils, margarine, processed meats like hot dogs and lunch meat should not be eaten on a regular basis.
  • Artificial sweeteners — This includes aspartame and sugar alcohols. They can have a negative effect on gut health and may push you out of ketosis. Avoid or eaten sparingly.
  • Alcohol — Alcohol can be high in carbs. It also puts stress on the liver and is best avoided while on the keto diet. As a splurge and if it helps you to stick with the keto diet, a low-carb beer or glass of red wine can occasionally be enjoyed.

KEYS TO SUCCESS ON THE KETO DIET

COOK FOR YOURSELF

The best foods on the keto diet are ones you prepare for yourself because you can track your macros and weigh and measure your portions. Feel free to experiment, but also compile a list of your favorite recipes so you don’t have to think too hard about what to make for those days when you’re short on time and patience.

ALWAYS THINK LOW-CARB

The keto diet is different than most other diets because it helps you to eat fewer calories without feeling hungry. By sticking to foods that are low in carbs, you will soon cease to crave them, and you will also get off the sugar roller coaster that once sent you to the snack machine every afternoon.

TRACK YOUR MACROS

keto macro tracking

Keeping track of your macros is key. Studies show that we underestimate how much we’re eating, often by a lot. This can lead to weight-loss plateaus, or even weight gain, which can be super discouraging. To keep this from happening, track your macros using an app such as MyFitnessPal and use a food scale.

AVOID YOUR TRIGGERS

Food being available 24/7 is not something humans have ever experienced before in history, and we see the consequences in skyrocketing obesity rates. Being endlessly bombarded with food is overwhelming to our willpower, and the complete lack of effort it takes to obtain food is wreaking havoc on our body and health. The best way to manage this tsunami of easy junk food is to only keep keto-friendly foods in your home.

Also, engage in meal-planning so when you get home tired and hungry from work, you don’t have to think too hard about what to eat. Do not keep too many convenience foods around, even if they are keto-friendly. Macademia nuts are keto, but eating an entire bag in one sitting is not good for you.

Finally, make a promise to yourself to only eat foods you measure and track. A bite here and a nibble there add up, messing with your weight loss goals.

FIND A COMMUNITY

Sticking to a healthy diet can be even more difficult if your friends are gobbling up pizza and slurping down soda. But if you hang with others who are also following a keto diet, it can be very helpful for when you’re struggling. You may also have questions about the diet and a community of keto dieters often has the answer. There is strength in numbers. Finding your clan can help you to stay strong.

BE PREPARED

Like the boy scouts, it’s best to be ready for any situation, and starting a new diet may be uncharted territory. Because the keto diet can cause you to quickly lose water and certain minerals such as sodium, some people experience symptoms like dizziness, brain fog, sugar cravings, nausea, and cramping. These symptoms are commonly called the ‘keto flu,’  and they are temporary. You can help them to go away even faster by drinking plenty of water and eating mineral-rich foods, and possibly even taking a mineral supplement until you’ve gotten through this brief phase.

COMMON MYTHS ABOUT THE KETO DIET

KETO IS IMPOSSIBLE TO STICK TO LONG-TERM

This could be said of just about any diet based on eating whole, fresh, natural foods you prepare yourself. It’s much easier to grab a pizza and a soda or a sugary coffee drink at the drive-thru than it is to plan ahead and bring a healthy snack with you (or not work such long hours that you have time to cook a healthy dinner). But the truth is that the list of ketogenic-compatible foods can be put together in endless combinations.

THE ONLY REASON TO DO KETO IS TO LOSE WEIGHT

The ketogenic diet can definitely help you to shed pounds quickly, but it can do so much more. The keto diet has been shown to reverse metabolic syndrome which can lead to diabetes, as well as lower your risk for heart disease.

The keto diet helps to curb cravings for sugar and other foods and help you get off the energy roller coaster. It has the potential to increase your longevity by reducing your risk of many chronic illnesses including cancer, heart disease, diabetes, autoimmune disorders, chronic fatigue, and more. It can decrease symptoms of depression, improve cognitive function and boost your energy levels.

The keto diet can dramatically lower inflammation in the body, which is known to factor into most major illnesses, as well as alleviate inflammatory skin problems like eczema. The keto diet also does good things to you body on a cellular level. It’s called mitochondrial biogenesis and it’s a little complicated, but basically, it’s like cleaning house, clearing out old, broken-down cells and rebuilding anew.

KETO IS A MEAT-BASED DIET

Keto is a fat-based diet. Protein is only eaten in moderate amounts because the body can convert protein into glucose, which can kick you out of ketosis. Healthy fats come from plenty of vegetable sources, including olives, avocados and coconuts, as well as animal sources like butter, cream, and steak. It is possible to be a vegetarian or even vegan and still follow the keto diet.

What to eat on Keto

KETO IS LOW IN FIBER, WHICH IS BAD

This idea probably stems from the myth that keto is meat-based. You do need fiber for a healthy gut and good digestion. The carbs in the keto diet come from vegetables that contain fiber, such as spinach, broccoli, avocados, asparagus, and cauliflower. For most people, switching from a standard American diet to a keto diet will result in an increase in fiber.

It is also important to note that by eliminating processed carbs and sugar from the diet, undesirable microbes like candida go away as well, which is excellent news for your digestive health.

COMMON MISTAKES ON THE KETO DIET

EATING TOO LITTLE FAT

Decades of fear-mongering has made people afraid to eat fat. Getting used to eating a high-fat diet can take some time and is not always easy to do. To be successful with the keto diet, you must remain in ketosis for as long as possible, thus the need to eat enough fat. Because of the way your body responds to fat consumption, it’s actually hard to overdo it on healthy fats.

EATING THE WRONG KIND OF FAT

While eating the right kind of fats is good, eating junky fats is not. Vegetable oils and seed oils, margarine, hydrogenated and otherwise processed fats are very unhealthy and will wreak your diet. Olive oil, fish oil, coconut oil and organic saturated fats from animals like meat, butter and eggs are what you want to eat.

Good vs. Bad Fats

EATING CONVENIENCE KETO

Stuff that comes pre-packaged is not what you want to be eating. Sure, there are times when you’re stuck and a Slim Jim is all you can get your hands on, but the vast majority of the food you eat should be real, whole food.

EATING TOO MANY HIDDEN CARBS

Carbs and sugar are lurking everywhere in pre-made foods. This is why it is so important to prepare your own meals. Eating too many carbs will throw you out of ketosis, and it can take days to get back it. Know what you’re eating, and make sure it is wholesome, natural, and low in carbs.

EATING TOO MUCH PROTEIN

This goes along with the common myths. Keto is not based on protein, but rather on fat. While protein is essential for building muscle (and other important soft tissues, like your internal organs), too much can kick you out of ketosis. For every 100 grams of protein, the body can convert more than half into glucose. One really great thing about ketosis is that that it causes something called protein sparing, meaning ketosis helps to keep the protein in your body and not burn it up for fuel the carb-heavy foods do.

OBSESSING OVER MACROS AND/OR THE SCALE

Yes, tracking your macros matters. And presumably you care about how much you weigh, and are likely to be looking to drop a few pounds. But obsession is never good. Following a keto diet isn’t meant to be a jail sentence. At first, you will spend more time figuring out what to eat, but once you find a good plan, you shouldn’t need to spend a significant portion of your day thinking about food.

STRESSING OVER CHOLESTEROL LEVELS

The fear of cholesterol goes hand in hand with the fear of fat. Cholesterol is necessary for the healthy function of every cell in your body. The ‘cholesterol is bad’ idea is just a big myth promoted by a guy named Ancel Keys who was looking to advance his career way back in the 1950s. For some reason and despite plenty of evidence to the contrary, we’re still stuck on his phony sales pitch about the evils of fat and cholesterol.

HOPING FOR THE QUICK FIX

You can’t just ‘go keto’ for a week or 2 and then go back to your old habits and expect lasting weight loss. Any healthy diet requires long-term commitment and keto is no different.

GOING AT IT ALONE

Changing your diet is difficult enough, but it can be overwhelming without support. A friend who is willing to help you stick to your plan is invaluable when you’re making this type of life change. If you don’t have anyone in your life like that, there are online support groups where people discuss their journey and struggles, and help cheer each other along.

MAKING COMPARISONS

While it is important to find your tribe of fellow keto-ers, everybody is different. Don’t base your progress, success or failure on what is happening with someone else. This is true for all of life and not just with diet.

EATING BASED ON THE CLOCK

The clock on the wall knows nothing about what’s going on in your body. If you’re not hungry in the morning, don’t eat. Likewise, if you are hungry in the morning, go ahead and have something. Listen to what your body is telling you rather than relying on external, artificial means of telling you when and what you ‘should’ eat.

COMMON QUESTIONS ABOUT THE KETO DIET

ISN’T FAT BAD FOR YOU?

This myth is deeply engrained in our lives, but it is simply not true. Look where this has gotten us: obesity rates are through the roof as we eat high-carb, low-fat foods.

WON’T I FEEL TIRED WITHOUT CARBS?

There will likely be an adjustment at the beginning of your keto diet, but once you get through that, you’ll feel your energy level soar. Even better, you’ll have steady energy throughout the day, and the ups and downs of sugar highs and crashes will vanish.

ISN’T IT BAD TO EAT A LOT OF MEAT?

Eating a lot of protein can be hard on your kidneys, but with the keto diet, you only consume a moderate amount of protein. Not more than 20% of your total intake should come from protein. Vegetables figure prominently in the keto diet, and fats do not hurt the kidneys.

HOW DO I KNOW WHEN MY BODY IS IN KETOSIS?

You can buy urine strips, a breath analyzer or use a blood meter to test if you are interested. But even without testing, there are several signs that can tell you whether you are in ketosis: a decrease in appetite and an increase in energy; ‘keto breath’ (a strong, fruity smell), dry mouth or a metallic taste in the mouth; and an increase in thirst and urination are all likely signs of ketosis.

keto testing

HOW LONG DOES IT TAKE TO GET INTO KETOSIS?

It depends on the individual. It can be as fast as one day or take a week or longer. For those who are insulin-resistant (such as people with type II diabetes), it often takes longer.

HOW MANY CARBS CAN I EAT AND STAY IN KETOSIS?

At first, the recommended number is 20 grams of carbs per day, and they should come from vegetables. However, many people can tolerate more, particularly those who exercise, and they may be able to have up to 50 grams each day.

IS THE KETO DIET SAFE?

The keto diet is safe for most people to follow. The exceptions are: diabetics, those taking high blood pressure medication, and pregnant and breastfeeding women. In these cases, the individual should consult with their doctor before starting the keto diet.

KETO VS PALEO

While there are some similarities between keto and paleo, there are several significant differences. The first one being that with keto, the goal is to stay in ketosis for as long as possible. You may enter ketosis while following a paleo diet, but it is not the goal of paleo.

With paleo, the main focus is on consuming fresh, natural, nutrient-dense foods. It is also important to eat high-quality foods on keto, but it is not the most important point. For keto, consuming a lot of fat is what matters.

Finally, the keto diet requires a very low intake of carbs. Paleo contains fewer carbs than the standard American diet, but it usually has more carbs than keto, which is why doing Paleo will often not result in entering ketosis.

KETO VS ATKINS

Both Atkins and keto involve restricting carb intake and you don’t have to count calories with either one. The biggest difference is the amount of protein you can eat. With keto, protein remains limited to 20% of your total intake while with Atkins, protein is unlimited.

There are some differences with carb intake as well. With keto, carbs are always limited while on Atkins, it depends. Atkins has four phases, the first of which is a lot like keto with carbs limited to 20-25 grams per day. As you progress through the phases, however, you are allowed to add carbs back in, up to 100 grams per day by phase 4.

KETO VS CARNIVORE

The carnivore diet is simple enough to understand: you eat only meat and animal products and drink water (although coffee is allowed in moderation but without sugar, of course). The carnivore diet is designed to help you lose weight fast, increase energy, improve mental clarity, as well as clear up skin conditions, and it’s simple — if not easy — to follow.

While both are high in fat and low in carbs, with keto, you need to track your macros and keep them to certain measurements of 70-80% fat, 15-20% protein and 5% carbs. With the carnivore diet, you don’t count macros or calories; you simply eat until you feel satisfied. While your carbs are low in keto (ideally 20 grams or fewer per day), with carnivore you consume zero carbs. Protein is also much higher with carnivore than with keto, which is kept moderate at around 20% of your total intake.

Another big difference between the two diets is that you do eat things besides meat on keto, particularly vegetables. Carnivore is extremely strict: no desserts, ever, while with keto you can make keto ice cream and fat bombs, or have nuts as a snack.

Perhaps the biggest difference between the two is that ketosis is not the point of the carnivore diet. It may happen, but because the body can convert protein into glucose, you will not automatically stay in ketosis while eating a carnivorous diet.

BEST KETO DIET SUPPLEMENTS

  • Electrolytes — Carbohydrates cause the body to retain water, and when you go low-carb you don’t retain as much. Taking electrolytes can help prevent dehydration, as well as lessen the effects of the initial phase of adjusting to the keto diet.
  • MCT oil — Medium-chain triglyceride oil helps you to feel full by releasing the hormone leptin. It is easily converted to ketones, which can help you stay in ketosis. MCT oil is also an instant source of energy that is able to cross the blood-brain barrier, meaning it can feed your brain. This is why MCT oil is so popular amongst keto dieters.
  • R-ALA — One of insulin’s jobs is to remove sugar from the blood stream. Being insulin resistant means your body no longer responds the way it should to sugar in your system. Excess sugar in your bloodstream can cause serious health issues. Alpha lipoic acid (R-ALA) has been proven to increase insulin sensitivity, which in turn improves the metabolism of sugar.
  • Chromium — Chromium is a mineral that has also been shown in studies to increase insulin sensitivity, helping your body to process sugar more effectively.
  • Exogenous ketones — Ketones can be made by the liver, but you can also take them as a supplement and that’s all that ‘exogenous’ means. MCT oil is an example of an exogenous ketone. You don’t need them every day, but they can help keep you in ketosis if you go a little overboard on the carbs.

KETO DIET RECIPES & RESOURCES

KETO DIET STUDIES

PROPONENTS OF THE KETO DIET

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Leslie Waterson

Leslie has been passionately involved in the health and fitness industries for over a decade. She is constantly reviewing the latest scientific research and studies in order to take a research-backed approach to lifestyle optimization. Her main areas of interest include nutrition and supplementation. Leslie shares her findings on Fitness Clone to help other health enthusiasts choose the products and routines that will help them achieve their goals.