1. Introduction: What is keto?
What “keto” means
The “keto” in a ketogenic diet comes from the fact that it makes the body produce small fuel molecules called “ketones”.
This is an alternative fuel for the body, used when blood sugar (glucose) is in short supply.Ketones are produced if you eat very few carbs (that are quickly broken down into blood sugar) and only moderate amounts of protein (excess protein can also be converted to blood sugar).
Ketones are produced in the liver, from fat. They are then used as fuel throughout the body, including the brain. The brain is a hungry organ that consumes lots of energy every day,
and it can’t run on fat directly. It can only run on glucose… or ketones.On a ketogenic diet, your entire body switches its fuel supply to run almost entirely on fat. Insulin levels become very low, and fat burning increases dramatically. It becomes easy to access your fat stores to burn them off. This is obviously great if you’re trying to lose weight, but there are also other less obvious benefits, such as less hunger and a steady supply of energy.
When the body produces ketones, it’s said to be in ketosis. The fastest way to get there is by fasting – not eating anything – but nobody can fast forever.
A keto diet, on the other hand, can be eaten indefinitely and also results in ketosis. It has many of the benefits of fasting – including weight loss – without having to fast.
Learn more about ketosis
Who should NOT do a ketogenic diet?
A keto diet is safe for most people, but in the following situations you may need extra support:
- Are you on medication for diabetes, e.g. insulin? Learn more
- Are you on medication for high blood pressure? Learn more
- Are you breastfeeding? Learn more
Are you a doctor or do you need your doctor to help you with medications on keto? Check out our keto for doctors guide.
2. What to eat on a keto diet
Here are typical foods to enjoy on a ketogenic diet. The numbers are net carbs per 100 grams.
To remain in ketosis, lower is generally better:
The most important thing for reaching ketosis is to avoid eating too many carbohydrates. You’ll probably need to keep carb intake under 50 grams per day of net carbs, ideally below 20 grams. The fewer carbs, the more effective.
Counting carbs can be helpful at first, but if you follow our guides and recipes you can stay keto even without counting.
Detailed list of what to eat on keto
Try to avoid
Here’s what you should not eat on a keto diet – foods full of sugar and starch, including starchy foods like bread, pasta, rice and potatoes. As you can see, these foods are much higher in carbs.
The numbers are grams of net carbs per 100 grams, unless otherwise noted.
This means that on keto you’ll need to completely avoid sweet sugary foods, plus starchy foods like bread, pasta, rice and potatoes. Just follow our keto diet advice, and remember that the food should be high in fat, not high in protein.
A rough guideline is below 10% energy from carbohydrates (the fewer carbs, the more effective), 15-25% from protein (the lower end is more effective), and 70% or more from fat.
More specific advice on what to eat – and what not to eat
What to drink
So what do you drink on a keto diet? Water is perfect, and so are coffee or tea. Ideally, use no sweeteners. A modest amount of milk or cream is OK (but beware of caffe latte!). The occasional glass of wine is fine too.
Check out our full guides to keto drinks and keto alcohol.
Visual keto guides
For more on specific areas – like what fruits or nuts to eat on a ketogenic diet – check out our visual guides:
Check out our hundreds of keto recipes, or a few popular examples below:
Here are two weeks worth of recipes for breakfast, lunch and dinner on a ketogenic diet:
14-day keto diet plan
Get lots of weekly keto meal plans, complete with shopping lists and everything, with our premium meal planner tool (free trial):
How low carb is keto?
The fewer carbohydrates you eat, the bigger the effects on weight and blood sugar will be. A keto diet is a very strict low-carb diet, and thus highly effective.
Here are three examples of what a low-carb meal can look like, depending on how many carbs you eat per day. Note that only the left plate is reliably ketogenic:
We recommend following the dietary advice as strictly as you can. When you’re happy with your weight and health, you may carefully try eating more liberally (if you want to). Learn more
4,301 viewsMake it simple to understand keto and do it right, using our new video course.Check out the first part above, the rest is instantly available with a free trial (no commitment, cancel online anytime).
For everything you need to get started – meal plans, shopping lists, daily tips and troubleshooting – just sign up for our free 2-week keto low-carb challenge.
Keto advice in 40 languages
We have written keto diet advice in 40 languages. This includes our full Diet Doctor sites in Spanish or Swedish. Press this small grey note symbol for more languages:
3. Why eat keto – the benefits
The benefits of a keto diet are similar to those of other low-carb diets, but it’s more powerful than liberal low-carb diets. Think of keto as a super-charged low-carb diet, maximizing the benefits.
Turning your body into a fat-burning machine has obvious benefits for weight loss. Fat burning is vastly increased, while insulin – the fat-storing hormone – levels drop greatly. This creates ideal circumstances in which fat loss can occur, without hunger.
More than 20 high-quality scientific studies
show that, compared to other diets, low-carb and keto diets result in more effective weight loss.
On keto you’ll gain a new control over your appetite. When your body burns fat 24-7, it has constant access to weeks or months of stored energy, dramatically reducing feelings of hunger. It’s a very common experience, and studies prove it.
This makes it easy to eat less and lose excess weight – just don’t eat until you’re hungry. This makes intermittent fasting easy, super-charging efforts to reverse type 2 diabetes and speeding up weight loss. Plus, you’ll save tons of time and money by not having to snack all the time. Many people only feel the need to eat twice a day (often skipping breakfast), and some just once a day.
Not having to fight feelings of hunger can also potentially help with problems like sugar or food addiction, and possibly some eating disorders, like bulimia, as well. At least feeling satisfied can be part of the solution. Food can stop being an enemy and become your friend – or simply fuel, whatever you prefer.
Constant energy and mental performance
Ketosis results in a steady flow of fuel (ketones) to the brain, and you avoid big blood sugar swings. This often results in the experience of improved focus and concentration. Any brain fog will be long gone!
A lot of people use keto diets specifically for increased mental performance. Also, many people experience an increase in energy when in ketosis.
On keto, the brain doesn’t need carbs. It’s fueled 24-7 by ketones, a perfect brain fuel for focus and energy.
Control blood sugar and reverse type 2 diabetes
A keto diet controls blood sugar levels, and is excellent for reversing type 2 diabetes. This has been proven in studies.
It makes perfect sense since keto lowers blood-sugar levels and reduces the negative impact of high insulin levels.As a keto diet may even reverse existing type 2 diabetes, it’s likely to be even more effective at preventing it, or reversing pre-diabetes.
150+ success stories
How to reverse type 2 diabetes – the quick start guide
Improved health markers
There are many studies showing that low-carb diets improve important health markers, including the cholesterol profile (HDL, triglycerides), blood sugar levels, insulin levels and blood pressure.
These commonly improved markers are connected to something called “metabolic syndrome”, and improvements in weight, waist circumference, diabetes type 2 reversal etc.
My health markers after 10 years on a keto diet
A calmer stomach
Keto can result in a calmer stomach, less (or no) gas, less cramps and pains, etc.
For quite a few people this is the top benefit, and it usually only takes a day or two to experience it. Learn more
Increased physical endurance
Keto diets can vastly increase your physical endurance by giving you constant access to all the energy of your fat stores.
The body’s supply of stored carbohydrates (glycogen) only lasts for a couple of hours of intense exercise, or less. But your fat stores carry enough energy to easily last for weeks or even months.
How to maximize endurance on a keto diet
The keto diet is a proven and effective medical therapy for epilepsy that has been used since the 1920s. Traditionally it was used primarily for children, but recently adults have benefited from it as well.
Using a ketogenic diet in epilepsy can allow people to take less or no anti-epileptic drugs, while still remaining seizure-free. This reduces drug side effects and thus increases mental performance. More
More possible benefits
The benefits above are the most common ones. But there are others that are potentially even more surprising and – at least for some people – life changing. Did you know that low carb often normalizes blood pressure, results in less acne, controls migraine and helps with a lot more?
Follow the links below for more knowledge, stories and science:
Other potential benefits
There’s even science-based speculation that a keto diet could increase longevity and help treat or reduce the risk of cancer.
It’s also being used as an experimental treatment for some people with Parkinson’s disease
We have received hundreds, if not thousands, of low-carb success stories, and we get more every day. Here are a few, and links to all of them are sorted by categories:
Reversing type 2 diabetes in only 2.5 months with keto and fasting
Keto and intermittent fasting: “I am completely blown away by the changes”
How Melissa lost 100 pounds with a keto diet, and kept it off for 15 years
Minus 125 pounds and no more binge eating on a keto diet
The keto diet: “It’s unbelievable that it could be this easy”
A low-carb diet: Maintaining a 70-pound weight loss for five years
4. How to know you’re in ketosis
How do you know if you’re in ketosis? It’s possible to measure it by testing urine, blood or breath samples. But there are also telltale symptoms, that require no testing:
Other, less specific but more positive signs include:
- Reduced hunger. Many people experience a marked reduction in hunger.
This may be caused by an increased ability of the body to be fueled by its fat stores. Many people feel great when they eat just once or twice a day, automatically ending up doing a form of intermittent fasting. This saves both time and money, while also speeding up weight loss.
- Increased energy. After a few days of feeling tired (the “keto flu“) many people experience a clear increase in energy levels. This can also be experienced as clear thinking, a lack of “brain fog” or even a sense of euphoria.
How do you measure ketosis?
There are three ways to measure for ketones, which all come with pros and cons:
- Urine strips
- Breath ketone analyzers
- Blood ketone meter
1. Urine strips
Urine strips are the simplest and cheapest way to measure ketosis. It is the first option for most beginners.
Dip the strip in your urine, and 15 seconds later the color change will show you the presence of ketones.
If you get a high reading (a dark purple color), you’ll know that you’re in ketosis.Pro: Ketone strips are available in regular pharmacies or via Amazon, and they’re very cheap. A strongly positive test reliably proves that you’re in ketosis.
Con: Results can vary depending on how much fluid you drink.
The strips don’t show a precise ketone level. Finally, and most importantly, as you become increasingly keto-adapted and your body reabsorbs ketones from the urine, urine strips may become unreliable, even if you’re in ketosis.
Thus, the test may sometimes stop working – always showing a negative result – when you’ve been in ketosis for several weeks.Order urine strips at Amazon
2. Breath-ketone analyzers
Breath-ketone analyzers are a simple way to measure ketones
in your breath. At $169 and up they are more expensive than urine strips. But they are cheaper than blood-ketone meters in the long run, as they are reusable any number of times.These analyzers do not give you a precise ketone level when used on their own, but provide a color code for the general level.
You can also hook it up to a computer or mobile phone (newer models) and get an exact ketone number via the app. Research shows that the device gives a decent correlation with blood ketones in most situations.Pro: Reusable, simple test.
Con: Does not always correlate well with blood ketones. Not always accurate, and can in some situations show entirely misleading values.
More expensive than urine strips, and higher cost upfront than a blood meter.Order Ketonix
Using breath-ketone analyzers
3. Blood-ketone meters
Blood-ketone meters show an exact and current level of ketones in your blood.
They are the gold standard and the most exact way to measure your ketosis level. The major disadvantage, however, is that they are quite expensive, formerly at least $2 per test.
Now a new startup, called Keto-Mojo, is offering blood ketone testing for as little as $1 per test. Early reviews are positive, and if you’re concerned about the price of testing, we recommend using the Keto-Mojo meter.
GOOD: Exact, reliable.
BAD: Still expensive (at least $1 per test). Requires pricking your finger for a drop of blood.
Order the Keto-Mojo meter
Order the blood-ketone meter Precision Xtra with everything included, at Amazon
5. How to reach optimal ketosis
Getting into ketosis is not a black or white thing. It’s not like you’re either in ketosis, or out of ketosis. Instead, you can be in different degrees of ketosis, as this chart demonstrates.
The numbers below refer to values when testing blood ketone levels.
- Below 0.5 mmol/l is not considered “ketosis”, although a value of, say, 0.2 demonstrates that you’re getting close. At this level, you’re still far away from maximum fat-burning.
- Between 0.5 – 1.5 mmol/l is light nutritional ketosis. You’ll be getting a good effect on your weight, but perhaps not optimal.
- Around 1.5 – 3 mmol/l is called optimal ketosis and is recommended for maximum mental and physical performance gains. It also maximizes fat burning, which can increase weight loss.
- Over 3 mmol/l is higher than necessary. It will achieve neither better nor worse results than being at the 1.5–3 level. Higher numbers can also sometimes mean that you’re not getting enough food (“starvation ketosis”). For type 1 diabetics, it can be caused by a severe lack of insulin that requires urgent attention.
- Over 8–10 mmol/l: It’s normally impossible to get to this level just by eating a keto diet. It means that something is wrong. The most common cause by far is type 1 diabetes, with severe lack of insulin.
Symptoms include feeling very sick with nausea, vomiting, abdominal pain and confusion. The possible end result, ketoacidosis, may be fatal and requires immediate medical care. Learn more
How to achieve ketosis
There are many things that increase your level of ketosis. Here they are, from most to least important:
- Restrict carbohydrates to 20 digestible grams per day or less – a strict low-carb diet. Fiber does not have to be restricted, it might even be beneficial.
How much is 20 grams of carbs? Use our visual guide to find out
- Restrict protein to moderate levels. If possible, stay at or below 1 gram of protein per day, per kg of body weight – about 70 grams of protein per day if you weigh 70 kilos (154 pounds).
The most common mistake that stops people from reaching optimal ketosis is too much protein. Our keto recipes are designed with the right amount of protein
- Eat enough fat to feel satisfied.
This is the big difference between a keto diet and starvation, that also results in ketosis. A keto diet is sustainable, whereas starvation is not. Our keto recipes have the needed fat included
- Avoid snacking when not hungry. Unnecessary snacking slows weight loss and reduces ketosis. Though using keto snacks will minimize the damage, and is fine when you’re hungry.
- If necessary, add intermittent fasting, like 16:8. This is very effective at boosting ketone levels, as well as accelerating weight loss and type 2 diabetes reversal.
- Add exercise – adding any kind of physical activity while on low carb can increase ketone levels moderately. It can also help speed up weight loss and diabetes type 2 reversal slightly.
- Usually not necessary: Supplement MCT oil and/or Bulletproof coffee.
- Usually not necessary: Supplement exogenous ketones.
Stories about achieving long-term ketosis
Here are the three reports from a 2-month experiment in reaching optimal ketosis:
- Experiment: Optimal ketosis for weight loss and increased performance
- Four weeks of strict LCHF and ketone monitoring
- Final report: Two months of strict LCHF and ketone monitoring
Do I have to reach optimal ketosis to experience the benefits?
In short, no. Many of the benefits, such as weight loss, are experienced at lower levels of ketosis (above 0.5). But you might need to reach higher levels of ketosis for high-level physical performance.
Learn keto from the experts
6. Keto tips and guides
To make keto truly simple and enjoyable requires a few new skills. For example, how do you cook keto breakfasts that you love? How do you eat more fat? And what’s important to think about when dining out?
Here are all the guides you need.
Breakfast is a great time to eat keto. Who doesn’t love bacon and eggs? If you don’t, there are great keto options with no eggs at all.
Another strong option is to just have a cup of coffee, as many people get less hungry on a keto diet and don’t really need breakfast. There are many other options – both delicious and fast
So, what’s for lunch and dinner? You could for example have meat, fish or chicken dishes with vegetables and a rich full-fat sauce. There are a million alternatives.
Check out this guide to learn to cook amazing keto meals
How to make keto cheap
A keto diet doesn’t have to be expensive. In this guide, you’ll learn how to make it super cheap
How to eat more fat
Fat is filling and an amazing flavor enhancer. But how do you get enough of it in your diet? And how much fat should you really eat? Hint: enough to feel satisfied and not hungry.
Here’s how to do it
Do you have a hard time living without bread?
There are good and bad keto options. Spoiler: you’ll probably want to stay away from “low-carb” bread from the grocery store! Here’s why, and what to do instead
How do you eat keto at buffets, at a friend’s house or at fast-food restaurants? Avoid the starchy foods (like bread or pasta) and ask for additional natural fat, like butter or olive oil, if you need it. Learn more
To cheat or not to cheat? This guide will help you decide, and if you do decide to cheat, it will help you do it smarter
Avoiding special products
Another common mistake on a keto diet is being fooled by the creative marketing of special “low-carb” products. Remember: An effective keto diet for weight loss should be based on real food.
Low-carb products like chocolate, candy, pasta and bread often use all kinds of deceptive marketing, while being just junk food – including carbs – in disguise. Learn more
Do you want more keto guides? We have more keto guides!
7. Potential side effects of ketosis
If you stop eating sugar and starch cold turkey (recommended) you may experience some side effects as your body adjusts. For most people these side effects tend to be mild and last a just few days. There are also ways to minimize them.
Another option is to decrease the intake of carbohydrates slowly, over a few weeks, to minimize side effects. But the “Nike way” (just do it) is probably the best choice for most people. Removing most sugar and starch often results in several pounds lost on the scale within a few days. This may be mostly fluids, but it’s great for motivation.
Here are side effects that may occur when you suddenly start a strict keto diet.
By far the most common side effect is called the keto flu, or induction flu. It’s what makes some people feel really bad 2-3 days after starting keto.
The most common symptoms:
- Light nausea
These side effects rapidly subside as your body adapts and your fat burning increases. Within a week, they are usually gone.
The reason for this is that carbohydrate-rich foods may increase water retention in your body. When you stop eating high-carb foods, you’ll lose excess water and salt through your kidneys, peeing more than usual. This can result in dehydration and a lack of salt during the first week, before the body has adapted, resulting in the above symptoms.
You can minimize the keto flu by drinking more fluids and by temporarily increasing your salt intake. A good option is to drink a cup of bouillon/broth 1-2 times a day. This will usually keep the keto flu minor or even non-existent.
Alternatively, drink a few extra glasses of water and put more salt on your food.
Learn more about keto flu and how to treat it
Other common issues on keto
Beyond the keto flu, there are five more relatively common side effects. Many of them can also be mostly avoided by getting enough fluid and salt.
There are also more things you can do to minimize any problems, click to read more if you’ve experienced one of these issues:
Less common issues
These are less commonly noticed issues that generally affect only a minority of people:
Beyond the usually minor and transient side effects that may occur (see above) there are tons of myths and fears that simply don’t hold up to closer scrutiny. For example, your brain is supposed to stop working unless you eat carbs. We’ll, that’s simply wrong.
Another common mistake is mixing up normal ketosis – resulting from a keto diet – with the dangerous medical emergency ketoacidosis. They are two very different things. Ketoacidosis does not happen just from eating a keto diet.
There are many more unfounded fears about keto, that are mostly based on myths and misunderstandings. Will it kill your kidneys or destroy your bones? Will it stop your thyroid from working? Read all about them on our low-carb and keto myths page
8. Keto Q&A, troubleshooting and resources
There are many common questions about keto, and we do our best to answer them all. Feel free to check out our full keto FAQ, or choose one of the questions below:
Resources to learn more
Get free video courses, keto recipes and news updates like over 500,000 people:
Here are a few of our hundreds of keto TV videos, these ones are focussed on keto basics:
Upcoming keto events
Do you want to meet other low-carb and keto fans and experts? Here’s an updated list of upcoming low-carb and keto events around the world
For more low-carb and keto sites, check out our recommended sites.
The Art and Science of Low-Carbohydrate Performance by Stephen Phinney and Jeff Volek.
Excellent two-part podcast where the top ketogenic diet researcher Dominic D’Agostino is interviewed by Tim Ferriss: part 1 / part 2 (D’Agostino is also active on Twitter).
Keto diet food list – what to eat
14-day keto diet plan