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The Keto Diet For Beginners: How It Works, Why It Works
This article has been written by experts and fact-checked by experts, including licensed nutritionists, dietitians or medical professionals. The information in the article is based on scientific studies and research.
It is designed to be honest, unbiased and objective, and opinions from both sides of an argument are presented wherever there is disagreement.
The scientific references in this article (marked by 1, 2, 3, etc.) are clickable links to peer-reviewed research material on the subject being discussed.
It’s virtually impossible to research diets – or even discuss weight loss with a group of friends – without hearing a lot about the keto diet.
Many medical experts and celebrities swear by keto – and there’s an excellent chance that you have friends or family members who’ve lost 10, 20, or 30 pounds while on the diet. Maybe more.
All that, and you get to eat lots of butter, cheese and bacon? Where do you sign up?
It’s important to understand that keto isn’t just a fad. It’s an accepted method for achieving fast weight loss. However, there are strict guidelines to follow if you want the diet to work.
Let’s learn about the ketogenic diet, starting from the very beginning.
What we now know as the keto diet didn’t go mainstream until the early 2010s when media outlets began carrying stories citing recent scientific studies. But similar low-carb diets had been around for nearly a century. They were an accepted medical treatment for some forms of childhood epilepsy starting in the 1920s.
Half a century later, popular weight loss regimens like the Atkins diet relied largely on reduced carbohydrate consumption, and similar diets like Paleo and South Beach followed in the early 2000s.
So low-carb eating was nothing new, and medical research into the subject accelerated as low-carbohydrate diets proliferated.
In 2013, the most important advancement was a study published in the journal Science. It found that the so-called ketogenic diet not only helped with weight loss but could provide numerous health benefits.
Subsequent publicity heightened interest in ketogenic eating, and just two years later, “keto diet” was the most-searched diet term on Google. Keto remains just as popular today.
Why Is It Called the Keto Diet?
Many diets rely on so-called “sensible” eating rules. Eat lots of vegetables and fruits, avoid junk food and sweet desserts, and you’re well on your way.
Those are good ways to lose weight slowly. But keto works much faster because it takes advantage of the way the body produces energy. And that’s where we meet the terms “keto,” “ketosis,” and “ketones.”
The Body and Energy
The way the human body works is complicated. The way it creates the energy it needs to function, though, is fairly straightforward.
The food we eat, primarily the carbohydrates in our diet, is broken down in the liver to create glucose (also known as blood sugar). Glucose powers our metabolism and our brain for normal daily function.
But what happens if the body doesn’t get enough carbs to make glucose?
First, it uses its limited supply of stored glucose, which is known as glycogen. When that’s been exhausted, the body goes into “emergency” mode to search for a different source of energy, by entering a metabolic state called ketosis.
In ketosis, stored body fat is burned to produce molecules known as ketone bodies (ketones for short). Not only can the body operate just fine on ketones, but there’s evidence that the brain performs even better on ketones than it does on glucose.
When the body’s carbohydrate intake returns to normal, so does its glucose production – and it no longer has to burn fat to produce large amounts of ketones.
If you’ve been reading between the lines, you already understand how depriving the body of carbohydrates can supercharge weight loss. But let’s spell it out.
Ketosis and Weight Loss
The ketogenic diet, more commonly shortened to “keto,” is designed to deprive the body of carbohydrates and force it into a state of ketosis. That’s when it will produce ketones to be used as a fuel source.
And as we’ve learned, large-scale production of ketones requires fat burning – the holy grail of weight loss. It’s really that simple; on the keto diet, the body is put into a metabolic state that encourages rapid weight loss.
Staying in ketosis is tricky, though. As soon as someone consumes enough carbs to restart glucose production, their diet is essentially over.
It doesn’t take much for that to happen. Even a single “cheat day” is likely to end ketosis and the resulting fat loss, and it can take as long as a week to get back into a fat-burning metabolic state.
That underscores something we said at the start: a successful keto diet requires adherence to strict guidelines.
If you follow the rules you could lose at least 1-2 pounds per week, after an initial loss of 5-8 pounds of water weight. If you ignore the rules when you feel like it, you can forget about rapid weight loss. You might even wind up gaining weight.
It’s time to talk about those rules.
Keto Diet: The Basics
Once again, we’ll start at the beginning.
Most of the essential nutrients we consume every day can be classified into one of three categories, collectively known as macronutrients. Those “macros” are protein, fats, and carbohydrates. (The other nutrients that we need in smaller amounts, like vitamins and minerals, are called micronutrients.)
Some foods are “all protein,” “all fat” or “all carbs,” but most of what we commonly eat contains some combination of the three macronutrients.
The keto diet is often billed as a low-carb diet. In reality, though, a proper balance of all three macros is crucial to staying in ketosis and losing weight on keto.
Carbohydrates and the Keto Diet
You probably have a very general understanding of carbohydrates. They’re essentially the sugars and starches in our diets.
On a low-carb diet, of course, you have to limit your daily carb intake. Shortly, we’ll get into the nuts and bolts of how that’s done. What’s important to understand first, though, is how big a change that can be.
(Important note: there are different types of keto. For now, we’ll be discussing “strict” keto diets which place the greatest restrictions on carbohydrate consumption.)
Federal recommendations for healthy eating suggest that normal adults should get 45-65% of their daily calories from carbs. When you do the math, you learn that a “healthy” diet contains between 225 and 325 grams of carbs per day.
On a strict keto diet? To achieve and remain in ketosis, you should be getting just 5% of your daily calories from carbohydrates. That equals 20-25 grams of carbs per day.
It’s not hard to see the drastic change in eating habits that a keto meal plan requires: you have to eliminate 90% of the carbs you’re accustomed to eating. Remember that fact; it will explain why the keto guidelines we’ll be discussing may seem draconian.
When you drop most carbs from your diet, of course, they have to be replaced by other macronutrients. Let’s talk about those next.
Fats, Protein and the Keto Diet
Those with just a passing knowledge of keto might think that you’re allowed to replace carbs with all of the bacon (protein) and butter (fat) you want to eat. That’s not quite true.
Keto guidelines change the “normal percentages” of macronutrients you consume, but the ketogenic diet still focuses on healthy eating. Even though you consume a lot more fat on keto, it should be healthy fat. You consume more protein as well, but it shouldn’t be unhealthy processed meat.
Since the keto diet is a low-carbohydrate, high-fat diet, let’s talk about fats first.
Federal dietary recommendations suggest that 20-35% of daily calories should come from fats. On keto, though, about 70-75% of daily calories ideally come from healthy fats. That means focusing on foods containing monounsaturated fats (like avocado and olive oil) and polyunsaturated fats that are high in Omega-3 fatty acids (like fatty fish and salmon).
By contrast, the partially-hydrogenated oils and trans fats commonly found in processed, packaged, and junk food are unhealthy fats and have no place in a successful keto diet.
If you’ve done the addition, you’ve discovered that about 20-25% of calories should come from protein when you’re on keto. Many adults already consume that much protein daily, so it doesn’t represent an enormous change for most people. That’s why keto is often called a moderate-protein diet.
This has all been a pretty good appetizer. It’s time to get to the main course of our Keto for Beginners guide.
Keto Diet: The Specifics
It would be terrific if keto guidelines were simple to follow. Unfortunately, they’re not.
Why Keto Can Be Complicated
There are hidden carbs in many healthy foods that you’re encouraged to eat on other diets.
And since the keto diet requires you to eliminate almost all dietary carbs, that means there’s a long list of “ordinary” foods you have to avoid.
The list includes obvious carb-laden culprits like cake and pasta. But some vegetables, most fruits, and almost all of the beverages you’re accustomed to drinking regularly are on the list as well.
That’s one issue; here’s a second. Since you’re limited to so few carbs per day, you have to understand how many you’re consuming.
For example, one slice of bread contains 15 grams of carbs (or in the usual keto shorthand, 15 carbs). You could eat that slice of bread, but it would use up almost your entire carb allowance for the day. You normally have a healthy glass of OJ in the morning? Oops. It contains 26 carbs, which may be enough – all by itself – to kick you out of ketosis and kill your diet.
So it can be complicated to follow a keto diet, at least until it becomes second nature.
A detailed rundown of every food you can and can’t eat on the keto diet could fill an entire book. For our purposes, let’s briefly look at each food category to get an idea of the foods on the “naughty” and “nice” lists.
Keto and Sugar
The white stuff you put into your coffee is sucrose, a pure carbohydrate. Brown sugar is made up of sucrose, fructose and glucose, all pure carbohydrates. In fact, almost every naturally sweet food you’ve ever eaten contains a form of sugar – meaning it’s loaded with carbs. Corn syrup, maple syrup, honey? All carbohydrates.
Sugar is what makes bakery goods, flavored yogurt, ice cream, soda, fruit juice, and other sweet foods taste good. Sadly, they’re all no-go on a strict keto diet.
There’s more to the story. An enormous range of packaged and processed foods contains added sugar. Tomato sauce, salad dressings, ketchup, and canned fruit are just a small sample of those foods whose added sugar can easily kill a keto diet. The easiest approach is to eat only whole, natural foods instead of stuff from the pantry or freezer.
Thanks to the huge popularity of ketogenic eating, however, there are a growing number of keto-friendly alternatives for sale. They can take some of the sting out of eliminating carbs from your diet.
What about using sugar substitutes?
Artificial sweeteners are technically low-carb and OK, but it’s been shown that they’re likely to increase cravings for real sugar. The best choices are natural “novel” sweeteners like monk fruit extract and stevia, which contain zero carbs and provide additional health benefits. So-called sugar alcohols like erythritol are also low-carb and suitable for cooking and baking.
Keto, Grains, and Starches
Sugars are simple carbohydrates, while grains and starches are generally complex carbohydrates. The latter may be somewhat healthier, but they’re still carbs. That makes them a big problem for keto dieters.
And there’s a very long list of grains and starches to avoid on the keto diet. We’ll start with grains like wheat, oats, rye, buckwheat, corn, and barley; that means foods like bread, cereal, pasta, tortillas, pizza, and crackers are out. Even the whole grains you’re encouraged to eat on most diets are a no-go on keto. Rice and quinoa are carb-laden and out, too.
Starchy vegetables are full of carbs, and that eliminates most veggies that grow below ground. Potatoes and sweet potatoes, corn, artichokes, parsnips, and beets top that list; onions and carrots are only OK in moderation.
What can you substitute? Many keto dieters opt for foods like cauliflower rice or cauliflower pizza, lettuce wraps, or “bread” made with almond flour. “Oopsie bread” made with cream cheese, eggs, and cream of tartar is another good choice.
Vegetables and Fruits
We’ve already mentioned that most root vegetables are starchy and not suitable for keto diets. Legumes like peas and beans are also carb-heavy and on the “naughty” list.
That leaves a wealth of above-ground veggies that are considered staples of keto eating plans. Leafy greens and just about all green vegetables, tomatoes and peppers, cukes and asparagus, cauliflower and broccoli? Go wild. Avocado is best of all, in all its forms.
Fruits are a very different story. Most contain high amounts of fructose, or fruit sugar, so they contain way too many carbohydrates for keto dieting. Small amounts of berries, watermelon, cantaloupe, and star fruit are essentially the only safe fruits when you’re on keto.
Just as carbs hide in fruit as fructose, they hide in milk and many other dairy products in the form of lactose (milk sugar).
You’re best off avoiding all types of dairy milk (including low-fat). Learning to love low-carb plant-based milks like almond, coconut, hemp or flaxseed is your best approach. Just be sure they’re unsweetened; you can guess what’s often used to sweeten nut milk.
There’s good news here, though. Most cheeses are OK in moderation; parmesan, asiago, mozzarella, brie, and blue cheese are among the lowest in carbs. Also fine in moderation: cottage cheese, cream cheese, sour cream, and Greek yogurt.
Heavy cream and butter get separate mentions here. They’re considered staples of keto dieting because they’re among the lowest-carb dairy products and they’re full of healthy fat. They do contain a lot of calories, though, so they’re not considered “unlimited” foods – just very good ones to include on keto.
Finally, an easy one.
You can eat virtually all proteins on a ketogenic diet: meat, poultry, fish, seafood, eggs – even hot dogs. But there’s one big difference between keto and most other diets: you don’t have to stick to lean meats and white meat poultry. Fatty cuts are a good way to get the extra fat you need on the keto diet.
Sticking with the overall theme of healthy eating, you should stick with high-quality proteins when possible. Grass-fed, free-range and wild-caught are the adjectives to look for because they contain more nutrients and fewer contaminants than commercially-raised proteins.
The only proteins you should definitely avoid have been heavily processed or breaded. For example, bacon is great; bacon with added sugar isn’t. Steak is terrific; chicken-fried steak is not.
Don’t overlook nuts and seeds, either. Many varieties like pecans, walnuts, flaxseeds, macadamia nuts, and chia seeds are high in protein and very low in carbohydrates.
Oils and Fats
Yes: Butter, olive oil (extra-virgin is best), avocado oil, coconut oil, sesame oil, walnut oil, lard, and ghee. Just use them in moderation. (Coconut oil is rich in MCTs, which are medium-chain triglyceride fats that help boost ketone production.)
No: Hydrogenated and partially-hydrogenated oils, trans fats, and margarine are out. Processed vegetable oils like canola, sunflower, corn, and soybean oils should be avoided as well.
That’s not all you can drink, but it’s the best zero-carb beverage there is. That also means black coffee is great for keto, as are all types of tea. Heavy cream, keto coffee creamers like Super Creamer, and novel sweeteners like monk fruit extract or stevia can provide variety.
Other common keto options include the unsweetened nut milks we’ve mentioned, and bone broth.
Bad news: soda, energy drinks, and fruit juices are out, and as we’ve already discussed, sugar-free sodas can make you crave sugar. Good news: spirits like whiskey, rum, gin, and vodka are all zero-carb beverages, and low-carb beer and wine are fine in moderation. Just skip the mixers, which are what make alcoholic beverages dangerous on the keto diet.
Condiments and Spices
Herbs and spices that grow naturally are ideal for use in keto recipes, as are salt and pepper. Mayo and mustard are usually OK, but the ketchup, BBQ sauce, salsa, and hot sauce you get at the store usually contain added sugar, as do salad dressings.
Homemade versions of those condiments are the way to go on keto. You can make yummy versions that are zero- or low-carb.
The keto-friendly commercial alternatives we’ve previously mentioned can be lifesavers, but one word of warning: always check ingredient labels before buying. No law prevents manufacturers from labeling foods “keto-friendly” when they’re really not.
Fast Food and Junk Food
Nope. They’re loaded with carbs.
It’s possible to eat in restaurants and still stay on a keto diet, but you have to be very careful to watch your carb consumption. More and more restaurants offer keto-friendly menu options, and those are the best places to patronize when you’re on a low-carb diet.
How Much of Everything Can You Eat?
The keto diet isn’t a golden ticket to eating as much as you want. Portion control is as important on keto as it is for any other type of healthy eating plan or weight loss regimen.
As for the amounts of each food you can eat, the best approach is to count carbs until you feel comfortable with the diet and its restrictions. In the early going, it’s essential to have a carb-counting app or a book that lists the number of carbs in each food. That will help you make sure you don’t fall out of ketosis in the early going.
Types of Keto Diets
We’ve been focusing on the guidelines for strict ketogenic dieting, which only allow you to consume 20-25 carbs per day. Some people, however, follow less-restrictive low-carb eating plans.
There are versions of “keto” that allow you to eat 50 carbs per day or even more. However, those diets are more likely to provide slow, gradual weight loss, since it’s easy to fall out of ketosis when you’re eating that many carbohydrates. The same applies to “cyclical” keto and intermittent fasting, which encourage the body to enter and leave ketosis regularly.
Another common approach is called “dirty keto,” on which you don’t worry about the “right” types of foods to eat as long as you keep your total carb consumption under your daily limit. Mixing in high-carb foods isn’t the best way to follow a keto diet, but it works for some people who get frustrated by having to avoid all the foods they love.
Finally, there are niche versions of keto which blend ketogenic guidelines with other diets to focus on specific types of food. They include Mediterranean keto, high-protein keto, and “clean” keto (an extremely healthy version of the diet).
Starting the Keto Diet
One word: patience.
Once you eliminate most carbs from your diet, it will take your body a few days (for some people, as long as a week) to use up all of its stores of carbohydrates and glycogen. Only then will you enter ketosis.
And the waiting may not be pleasant. As your metabolism shifts, you’re likely to suffer the symptoms of what’s known as the keto flu. Exhaustion, cramps, constipation or diarrhea, and frequent urination are the most common side effects, but insomnia and rashes are possible both in the beginning stages of keto and later in the diet.
The keto flu won’t last long. Hydration, mineral supplements and rest will help, and the benefits will be worth the discomfort. And from the glass-half-full department: the possibility of another bout of keto flu can encourage you to stay on your diet – so you don’t have to go through the flu again.
Speaking of benefits…
Health Benefits of Keto
Way back at the start of this beginner’s guide, we mentioned that the ketogenic diet originated as a treatment for some forms of childhood epilepsy. Since then, research has uncovered a wealth of other medical, health and wellness benefits that keto dieting appears to provide.
- Diabetes: Keto has been shown to lower blood sugar levels, triglycerides and cholesterol levels while dramatically improving insulin sensitivity.
- Heart Health: Keto dieting may reduce numerous risk factors for heart disease and metabolic syndrome, including high blood pressure, high levels of LDL (bad) cholesterol, and excess body fat. It may also boost HDL (good) cholesterol.
- Neurological Diseases: Studies show that keto may help fight degenerative diseases like Alzheimer’s disease and Parkinson’s disease, and aid recovery from traumatic brain injuries.
- Mental Focus: The brain appears to function more efficiently on ketones than glucose, leading to better clarity, attention span, focus, and memory performance.
Preliminary research has indicated there are many more potential benefits of keto. They include easing skin conditions, PCOS, migraines, digestive issues – and possibly even fighting some types of cancer. And of course, any diet effective at fighting obesity is going to boost overall health.
Are There Risks to Keto Dieting?
Some people should not start a keto diet without consulting their doctor, because carb restrictions may make their existing medical conditions worse. Those groups include type 1 diabetics and patients with liver failure or pancreatitis, gallbladder disease and eating disorders. Women who are pregnant or nursing should seek medical advice before trying keto.
Those with type 2 diabetes who take insulin may have a higher risk of low blood sugar (hypoglycemia) on a keto diet, so they should speak to their doctor as well.
One other group of dieters may not find keto the right choice: athletes and workout warriors. They derive much of their energy from carbohydrates, so they may not be able to maintain their exercise regimen when cutting carbs to very low levels. Consulting a dietitian would make sense first.
Many studies indicate that the ketogenic diet should only be followed for short periods, 30-90 days or so, before resuming a more normal eating regime. That’s because carb deprivation may lead to several health or medical issues over time:
- Lack of sufficient micronutrients
- Disruption of the gut biome, leading to digestive issues
- Atrial fibrillation, a heart rhythm disorder
- Ketoacidosis, a buildup of blood acids that can be dangerous, particularly to diabetics
None of those conditions are common, and they should not be a reason for healthy adults to fear short-term ketogenic dieting. However, it’s important for all dieters – whether they’re on the keto diet or another eating plan – to carefully monitor their physical condition and speak with a professional if they feel they may be experiencing problematic health conditions.
Keto vs. Other Diets
Healthy eating can help most people lose weight, and many science-based diets can accelerate weight loss.
However, studies have compared the keto diet to other popular eating plans like traditional low-fat diets and the Mediterranean diet. And results show that participants in controlled research lost more weight on keto than on those other respected diet plans.
Two possible reasons are that ketones may suppress hormones that make you feel hungry, and that protein and fat make dieters feel fuller than carbs do.
Whatever the reasons, the keto diet is a proven way to lose a substantial amount of weight more rapidly than other diets will allow.