A Ketogenic Diet for Beginners
A ketogenic diet (keto) is a very low-carb diet, which turns the body into a fat-burning machine. It has many potential benefits for weight loss, health and performance, but also some potential initial side effects.
A ketogenic diet is similar to other strict low-carb diets, like the Atkins diet or LCHF (low carb, high fat). These diets often end up being ketogenic more or less by accident. The main difference between strict LCHF and keto is that protein is restricted in the latter.
A keto diet is designed specifically to result in ketosis. It’s possible to measure and adapt to reach optimal ketone levels for health, weight loss, or for physical and mental performance. Below you can learn how to use keto to achieve your personal goals.
What is Ketosis?
The “keto” in a ketogenic diet comes from the fact that it makes the body produce small fuel molecules called “ketones” 1. 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 day2, 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, like for example 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 obviously it’s not possible to fast forever.
A ketogenic 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.
Who should NOT do a ketogenic diet?
Most people can safely do a ketogenic diet. But in these three situations you may need extra preparation or adaptation:
- 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
The Benefits of a Ketogenic Diet
The benefits that come from a ketogenic diet are similar to those of any strict low-carb diet. However, the effect might be even greater since protein is more restricted. This raises ketones more, and lowers insulin (the fat-storing hormone) more.
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.
Diabetes type 2 reversal
Improved mental focus
Ketosis results in a steady flow of fuel (ketones) to the brain. And on a ketogenic diet you avoid big swings in blood sugar. This often results in the experience of increased focus and improved concentration.
A lot of people specifically use keto diets specifically for increased mental performance.
Interestingly, there’s a common misperception that eating lots of carbs5 is needed for proper brain function. But this is only true when ketones are not available.
After a few days (up to a week) of keto-adaptation – during which people may experience some difficulty concentrating, have headaches and become easily irritated – the body and brain can run effortlessly on ketones.
In this state many people experience more energy and improved mental focus.
Increased physical endurance
Ketogenic 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.
When you’re adapted to burning primarily carbohydrates – like most people are today – your fat stores are not easily available, and they can’t fuel your brain. This results in constantly having to fill up by eating before, during and after longer exercise sessions. Or even just to fuel your daily activities and avoid “hanger” (hungry and irritable).
On a ketogenic diet this problem is solved. As the body and brain can easily be fueled 24/7 by your powerful fat stores, you can keep going forever like the Energizer Bunny.
Whether you are competing in a physical endurance event, or just trying to stay focused on reaching some other goal, your body has the fuel it needs to keep you going and going.
So how is it possible that most people believe that carbs are necessary to perform exercise? There are two reasons. To unlock the power of ketogenic diets for physical endurance, and not instead suffer reduced performance, you need:
- Enough fluid and salt
- Two weeks of adaptation to burning fat – it does not happen instantly
There are many studies showing that low-carb diets improve markers of metabolic syndrome6 such as blood lipids, insulin levels, HDL-cholesterol, LDL particle size and fasting blood sugar levels. Improvements have been shown to be even greater when carbs and protein are restricted to a the point of being steadily in nutritional ketosis.
The ketogenic diet is a proven medical therapy for epilepsy that has been used since the 1920s. Traditionally it has mainly been used in children with uncontrolled epilepsy despite medication.
More recently it has also been tested successfully by adults with epilepsy, with similar good results. There are many randomized controlled trials that demonstrate the effectiveness of the ketogenic diet in decreasing seizures in patients with epilepsy7.
Using a ketogenic diet in epilepsy is that usually allows people to take less anti-epileptic drugs, while remaining seizure-free. It’s not unusual to even be able to completely stop taking these drugs while staying seizure-free.
As all anti-seizure medications have side effects – like drowsiness, reduced concentration, personality changes or even reduced IQ – being able to take less or no drugs can be hugely beneficial.
Other possible benefits
What Do You Eat on a Ketogenic 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 to reach ketosis is to avoid eating most carbohydrates. You’ll probably need to keep carb intake to under 50 grams per day of net carbs12, ideally below 20 grams. The fewer carbs the more effective.
This means you’ll need to completely avoid sweet sugary foods, plus starchy foods like bread, pasta, rice and potatoes. Basically follow the guidelines for a strict low-carb diet, and remember it’s supposed to 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% protein (the lower end is more effective), and 70% or more from fat.
Here are examples of keto recipes:
Here are two weeks worth of recipes for breakfast, lunch and dinner on a ketogenic diet:
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Visual keto guides
For more on specific areas – like what fruits or nuts to eat on a ketogenic diet – check out our visual guides:
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:
How to Know You’re in Ketosis
How do you know 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:
- Dry mouth and increased thirst. Unless you drink enough and get enough electrolytes, like salt, you may feel a dry mouth. Try a cup of bouillon or two daily, plus as much water as you need.
- Increased urination – another ketone body, acetoacetate, can end up in the urine. This makes it possible to test for ketosis using urine strips. It also – at least when starting out – can result in having to go to the bathroom more often. This is the main cause of the increased thirst (above).
- Keto breath – this is due to a ketone body called acetone escaping via our breath13. It can make a person’s breath smell “fruity”, or similar to nail polish remover. This smell can sometimes also be felt from sweat, when working out. It’s often temporary. Learn more
Other, less specific but more positive signs include:
- Reduced hunger – many people experience a marked reduction in hunger14. This may possibly be caused by an increased ability of the body to be fueled by its fat stores. Many people feel great while eating 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 – perhaps 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 as 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 is the most simple and cheap way to measure ketosis. It is the first option for most beginners.
You dip the stick in your urine, and 15 seconds later the color change will tell you the presence of ketones15. 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 drink16. 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 ketosis17. Thus the test may sometimes stop working – always showing a negative result – when you’re been in ketosis for several weeks.
2. Breath ketone analyzers
Breath ketone analyzers is a simple way to measure ketones18 in your breath. At around $150 they are more expensive than urine strips. But they are cheaper than blood ketone meters in the long run, since they are reusable any number of times.
These analyzers do not give you a precise ketone level, but rather a color code for the general level. Research shows that there is decent correlation with blood ketones in most situations.
Pro: Reusable, simple test.
Con: Does not always correlate well with blood ketones. Not accurate, and can sometimes show entirely misleading values. More expensive than urine strips upfront than blood meter. Not portable, needs computer hookup to read..
Blood ketone meters show an exact and current level of ketones in your blood19. They are currently the gold standard and the most exact way to measure your ketosis level. The major disadvantage, however, is that they are quite expensive: A meter with 10 test strips included costs about $100 and then an additional $3 per test after that.
GOOD: Exact, reliable.
BAD: Expensive. Requires pricking your finger for a drop of blood.
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 demonstrates20. 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.
- Values of over 3 mmol/l aren’t necessary. That is, they will achieve neither better nor worse results than being at the 1.5–3 level. Higher values 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 attention21.
- Values of over 8–10 mmol/l are usually impossible to get to just by eating a ketogenic diet. It means that something is wrong. The most common cause by far is type 1 diabetes with severe lack of insulin22. Symptoms include feeling very sick with nausea, vomiting, abdominal pain and confusion. The end result can be a state called ketoacidosis, that may be fatal. Needless to say abnormally high ketones 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 beneficial23.
- Restrict protein to moderate levels. If possible stay at or below 1 gram of protein per day, per kg of body weight. So about 70 grams of protein per day if you weigh 70 kilos (154 pounds). It might be beneficial to lower protein intake even more, especially when overweight, and then aim for 1 gram of protein per kg of desired weight. The most common mistake that stops people from reaching optimal ketosis is too much protein.
- Eat enough fat to feel satisfied. This is the big difference between a ketogenic diet and starvation, that also results in ketosis. A ketogenic diet is sustainable, starvation is not.
- Avoid snacking when not hungry. Unnecessary snacking slows weight loss and reduces ketosis.
- 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.
- Usually not necessary: Supplement MCT oil and/or Bulletproof coffee.
- Usually not necessary: Supplement exogenous ketones24.
Two stories about achieving long-term 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
Here’s a great ten-minute presentation about self-tracking one year in nutritional ketosis:
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 (at least above 0.5). There are indications that you might need to reach higher levels of ketosis for high-level physical performance.
A master class in ketosis
Here’s a great presentation by Professor Jeff Volek, about the benefits of adapting your body to run on fat and ketones for fuel:
Do you want to understand what it takes to successfully and enjoyably reach and maintain long-term ketosis? Then there’s no better teacher than Professor Stephen Phinney. Get inspired here:
Potential Side Effects of Ketosis
Can ketones get too high, dangerously high? Not under normal circumstances.
For most people it’s quite a challenge to even get to optimal ketosis. Getting into dangerously high ketone levels (more than 8 – 10 mmol/l) is most often simply impossible. The main exception is type 1 diabetes, where the pancreas does not produce enough insulin. In type 1, it’s very possible to get dangerously high ketone levels – just by forgetting to take your insulin injection. There are also other situations like breastfeeding and taking type 2 diabetes medications called SGLT-2 inhibitors25 that in rare situations can result in too high ketone levels.
This will result in feeling sick, nauseous and very weak. It can develop into a life-threatening condition called ketoacidosis. There’s a simple treatment if you suspect this may be happening: eat some carbohydrates right away (e.g. a couple of fruits or a sandwich or a glass of juice). If you have type 1 diabetes take more insulin. Then contact emergency medical services if you do not immediately start feeling better.
The Keto Flu
While ketosis is normally safe, it is common to experience some time-limited side effects.
People transitioning from sugar-burning to fat-burning mode often initially experience side effects. This is referred to as the keto flu, since symptoms are similar to those of the flu: fatigue, nausea, headaches, cramps, etc. There are two main things that one can do to prevent or alleviate these symptoms:
- Drink water with salt and lemon – alternatively have a daily cup of bouillon.
- Gradually reduce carbohydrate intake – stopping suddenly results in more temporary symptoms
When starting on a ketogenic diet, you lose water and consequently electrolytes. This is happening since carbs retain water and salts in the body, so when you stop eating carbs your body loses this water. If the keto flu is happening due to too little hydration, it might help to drink a glass of salt water with a little bit of squeezed lemon (for taste).
When carbohydrates are suddenly removed from the diet, the brain can run slightly low on energy before it learns to use ketone bodies for fuel instead of sugar. This means that if you drastically reduce carbs from one day to another, you may get symptoms of such as tiredness, nausea and headaches. Replacing fluids and electrolytes as described above can alleviate the symptoms. Or by instead gradually lowering carb intake over a period of a week or more, the body gets used to burning fat and ketones instead of glucose and there will usually be no symptoms.
If you do not wish to gradually reduce carbs, make sure to get enough fluid and salt (like 1-2 cups of bouillon per day) to minimize symptoms. After a week or so the body is usually adapted to a ketogenic diet.
Dangers, Myths and Side Effects of the Ketogenic Diet
The side effects, potential dangers and myths around the ketogenic diet are virtually identical to other strict low-carb diets. Learn more about them here:
Alternatively choose a specific topic below.
The 6 most common problems when starting
Less common issues on keto / low carb
Low-carb & keto myths
Q&A, Fine-tuning and Troubleshooting
What’s the difference between low-carb and keto diets?
Keto is a very strict low-carb diet, that also puts even more emphasis on moderating the protein intake, and relying primarily on fat to supply energy needs.
A regular strict low-carb diet will likely put most people in ketosis anyway. But a keto diet tweaks things even further to make sure it’s working and, if desired, to get even deeper into ketosis.
Keto could be called an extra strict low-carb diet.
Should you aim for high ketone levels to speed up weight loss?
Yes and no. Eating less carbs, less protein and intermittent fasting certainly promotes weight loss, while lowering insulin and raising ketones.
However, adding extra fat to raise ketone levels does not promote weight loss. Neither does supplementing with MCT oil to raise ketone levels, or drinking “exogenous” ketone supplements. These methods actually slow down weight loss, by providing alternative fuel to be used instead of burning body fat.
If you want to lose weight only use these methods – MCT oil or exogenous ketones – when you are hungry, or for performance reasons (unrelated to weight loss).
Learn more: The Benefits of Ketones… Endogenous Ketones
At what time of day should you test ketone levels?
For comparison purposes it’s good to do it about the same time every day. Doing it in the morning before eating makes it most easy to compare the result from day to day.
However, morning values are usually among the lowest in the day, while evening values are higher. So if for some reason you want impressively high values, do it in the evenings instead. Be aware that your ketone levels don’t distinguish between the burning of dietary fat and stored fat.
More Low-Carb Questions & Answers
Resources to Learn More
Get free video courses, keto recipes and news updates like over 250,000 people:
Top ketosis videos
Ketogenic Diet Resource (very thorough, but not simple)
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:
- The Tim Ferriss Show: Dom D’Agostino on Fasting, Ketosis, and the End of Cancer (November 2015, interview)
- The Tim Ferriss Show: Dom D’Agostino — The Power of the Ketogenic Diet (July 2016, D’Agostino answers reader questions)
D’Agostino is also quite active on Twitter @DominicDAgosti2.
Do you have any suggestions on how to improve this page about ketogenic diets? Anything that is unclear or wrong? Any important information missing? Please let us know in the comments below.
There are three different ketones, or “ketone bodies” used as fuel by the body. They are:
Learn far more than you’ll ever need about ketones here:
and can run perfectly well on ketones. The brain consumes about 20% of the body’s required energy every day, despite only representing 2% of the body’s mass.
A good bonus for weight loss, if you can get your hungry brain to burn fat for you, 24-7. ↩
120 grams per day or more ↩
Volek, Jeff S. et al. Carbohydrate Restriction Improves the Features of Metabolic Syndrome. Journal of Nutrition and Metabolism, 2005. ↩
These two articles show how the ketogenic diet can be used to treat children with epilepsy:
- Kosoff, EH et al. Ketogenic Diets: An Update for Child Neurologists. Journal of Child Neurology, 2009.
- Kosoff, EH et al. Optimal Clinical Management of Children Receiving the Ketogenic Diet: Recommendations of the International Ketogenic Diet Study Group. Epilepsia, 2009.
Here’s a recent review article summarizing the science on the topic:
One small study has found improvement in memory in people with mild cognitive impairment, using a ketogenic diet:
- Krikorian, R et al. Dietary ketosis enhances memory in mild cognitive impairment. Neurobiology of Aging, 2012.
There are studies linking high, or even “normal”, non-diabetic blood sugar levels to dementia and Alzheimer’s. Since a ketogenic diet lowers blood glucose it could conceivably cut the risk of developing these diseases. Take a look at this study for instance:
Here are a couple of pilot studies where a ketogenic diet was used in cancer patients. The conclusions are that an insulin-inhibiting diet is safe and feasible in selected patients with advanced cancer.
- Fine, EJ et al. Targeting Insulin Inhibition as a Metabolic Therapy in Advanced Cancer. Journal of Nutrition, 2012.
- Tan-Shalaby, JL et al. Modified Atkins diet in advanced malignancies – final results of a safety and feasibility trial within the Veterans Affairs Pittsburgh Healthcare System. Nutrition & Metabolism, 2016.
In brain cancer in particular the ketogenic diet looks like a promising addition to other treatments:
- Frontiers in Molecular Neuroscience 2016: Tumor Metabolism, the Ketogenic Diet and β-Hydroxybutyrate: Novel Approaches to Adjuvant Brain Tumor Therapy
NOTE: This is only an experimental additional treatment of selected cancers, with highly limited evidence. Many conventional cancer treatments (surgery, chemo etc.) are highly effective and they often offer excellent chances of a cure when used in early stages of the disease. To turn down such treatment would be a mistake that could easily be fatal. ↩
A small pilot study of five people with Parkinson’s disease showed clear improvement of symptoms on a ketogenic diet. There was no control group, so a placebo effect can’t be ruled out.
Vanitallie, TB et al. Treatment of Parkinson disease with diet-induced hyperketonemia: a feasibility study. Neurology, 2005. ↩
Net carbs (or “digestible carbs”) are total carbs minus fiber. Fiber is OK to eat since it doesn’t affect blood sugar levels. ↩
This can sometimes be measured as early as during the first day on a ketogenic diet:
This has been clearly demonstrated in several scientific studies:
The strips measure for the ketone type acetoacetate. The presence of this in your urine indicates that you’re been in ketosis during the hours before testing. ↩
By drinking more water, you dilute the concentration of ketones in the urine and thus a lower level of ketones will be detected on the strips. ↩
This happens when the body becomes more adapted to using ketones, meaning that they increasingly stay in the blood to be used as energy instead of being lost through the urine. ↩
Breath analyzers measure the ketone acetone. ↩
Blood ketone meters measure the ketone beta-hydroxybyturate (BHB). ↩
The chart is from the excellent book The Art and Science of Low-Carbohydrate Performance by Professor Stephen Phinney and Jeff Volek. Highly recommended.
Take insulin, eat carbs (if your blood glucose isn’t already high), and contact medical services immediately. ↩
Fiber is digested by bacteria in the colon, and some of it is transformed into a fat called medium-chain triglycerides. This fat can be absorbed by the body and is very effective at turning into ketones. Thus eating more fiber (but still very low carb) could result in higher ketone levels in the blood. ↩
The company Prüvit sells drinkable ketones, called KETO//OS. This drink raises blood levels of ketones and may possibly improve physical and mental performance under certain circumstances.
However, it does not lower insulin or blood sugar, and it does not increase fat burning. Thus it hardly helps with weight loss or type 2 diabetes reversal.
Also note that they are selling through a multi-level marketing scheme, meaning their affiliates are paid on commission. So take all endorsements with a grain of salt.
E.g. Farxiga, Jardiance, Invokana ↩